GTK, Bulletin 412. Developments in Map Data Management And

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Bulletin 412 • Special Issue Bulletin Jarmo Kohonen and Timo Tarvainen (eds) (eds) Timo Tarvainen and Jarmo Kohonen geological unit nomenclature in Finland unit nomenclature geological Developments in map data management and and management data in map Developments Geological SurveyGeological Finland of

Geological Survey of Finland • Bulletin 412 • Special Issue • Jarmo Kohonen and Timo Tarvainen (eds) Geological Survey of Finland, Bulletin

The Bulletin of the Geological Survey of Finland publishes the results of scientific research that is thematically or geographically connected to Finnish or Fennoscandian geology, or otherwise related to research and innovation at GTK. Articles by researchers outside GTK are also welcome. All manuscripts are peer reviewed.

Editorial Board Dr Saku Vuori, GTK, Chair Dr Stefan Bergman, SGU Dr Asko Käpyaho, GTK Dr Antti Ojala, GTK Dr Timo Tarvainen, GTK, Scientific Editor

Instructions for authors available from the Scientific Editor. GEOLOGICAL SURVEY OF FINLAND

Bulletin 412

Developments in map data management and geological unit nomenclature in Finland

Jarmo Kohonen and Timo Tarvainen (eds)

Unless otherwise indicated, the figures have been prepared by the authors of the article.

https://doi.org/10.30440/bt412

Received 15.9.2020; Accepted in revised form 13.4.2021

Layout: Elvi Turtiainen Oy

Espoo 2021 Kohonen, J. & Tarvainen, T. (eds) 2021. Developments in map data management and geological unit nomenclature in Finland. Geological Survey of Finland, Bulletin 412, 169 pages, 41 figures, 18 tables and 4 appendices.

The ongoing transition from maps to 3D modelling of geology needs to be supported by efficient infrastructure, both within the Geological Survey of Finland (GTK) and nationally. One key component is the easy use of geological map data in forward modelling processes. In practice, this means consistency, standardization and traceability of all the interpreted map data.

The first paper (Ahtonen et al.) describes the structure of the new GTK Map Data Architecture (MDA) within the broader context of National Geological Framework of Finland (NGFF). MDA will be founded on three pillars: (1) structured spatial data, with the map objects and related attributes arranged as thematic layers; (2) structured non-spatial data (Finstrati databases for defined geological units; Finstruct database for major bedrock structures) and (3) linked documentation, including key references to the original geological descriptions and scientific content. The MDA is designed to meet the needs of various use cases and to enable access to all kinds of geological information.

The Precambrian crystalline bedrock of the Fennoscandian shield area is covered by a thin layer of superficial deposits of Quaternary age. The distinctly twofold characteristics of Fennoscandian geology are directly reflected in the mapping concepts and in the research tradition in Finland. The last three contributions of the volume consider the principles of geological map unit division. The second paper, “Terminology and division of tectonic-scale map units in Finland” (Kohonen et al.), clarifies the connection between the prevailing tectonic evolution models and the national bedrock map compilations. The new, coherent classification system for tectonic-scale map units consists of three categories: crustal province, tectonic province and structural province. The categories are conceptually independent, which allows both the subdivision and spatial overlapping of the map units. Key attributes for characterization of all the province categories are provided.

The third paper (Luukas & Kohonen) summarizes the current ideas concerning thrust tectonics in Finland. The new province division presented in the second paper has been utilized here in the arrangement of the thrust systems. The authors present a country-wide compilation of the major thrust-bounded units in Finland. All the units (nappes, allochthons and thrust stacks) are named, characterized and linked to the corresponding detachment.

The Quaternary superficial deposits were deposited on the bedrock mainly during and after the last glaciation as a result various glacial and postglacial processes. The fourth paper (Palmu et al.) presents a comprehensive and coherent system for the management of the superficial map units in Finland. The approach is based on four parallel systems: (1) glacial dynamic (GD) classification (provinces and regions), (2) morpho-lithogenetic (MLG) classification, (3) lithostratigraphic classification, and (4) allostratigraphic classification. The refined GD approach creates an overall map unit framework, whereas MLG classification is applied to interpretations of glacial landforms from high-resolution (2m grid) LiDAR DEM data. Lithostratigraphy and allostratigraphy are standard methods in type section based mapping and in marine geological surveys, respectively.

Keywords: Geological map data, map data architecture, classification system, map unit, Precam- brian, Quaternary, Finland

Jarmo Kohonen Geological Survey of Finland P.O. Box 96 FI-02151 Espoo Finland E-mail: [email protected]

Timo Tarvainen Geological Survey of Finland P.O. Box 96 FI-02151 Espoo Finland E-mail: [email protected]

ISBN 978-952-217-410-9 (pdf) ISSN 0367-522X (print), ISSN 2489-639X (online)

2 CONTENTS

Editors’ preface ...... 4 Jarmo Kohonen and Timo Tarvainen

GTK Map Data Architecture: the core of the developing National Geological Framework of Finland...... 7 Niina Ahtonen, Jarmo Kohonen, Jouni Luukas, Antti E. K. Ojala, Jukka-Pekka Palmu and Jouni Vuollo

Classification of regional-scale tectonic map units in Finland...... 33 Jarmo Kohonen, Raimo Lahtinen, Jouni Luukas and Mikko Nironen

Major thrusts and thrust-bounded geological units in Finland: a tectonostratigraphic approach ...... 81 Jouni Luukas and Jarmo Kohonen

Classification system for Superficial (Quaternary) Geological Units in Finland...... 115 Jukka-Pekka Palmu, Antti E. K. Ojala, Joonas Virtasalo, Niko Putkinen, Jarmo Kohonen and Pertti Sarala

3 Developments in map data management and geological unit nomenclature in Finland Edited by Jarmo Kohonen and Timo Tarvainen Geological Survey of Finland, Bulletin 412, 4–6, 2021

EDITORS’ PREFACE

All the contributions to this volume consider the management of geological map data. The main focus is on questions related to data architectures and underlying geological classification systems, not on information system technologies. All the examples represent activities by the Geological Survey of Finland (GTK), but the underpinning concepts are generic and basically applicable any- where with a similar geological environment.

The geological map – an anachronism?

Since the early 19th century, printed geological maps have formed the fundamental foundation in the representation of geological relationships in regional geology. A geological map is essentially a 2D model, an interpretation based on the compiler’s ideas of the geology, often supported by cross-sections, structural drawings and stratigraphic diagrams. The traditional geological mapping has been under pressure: the relevance of the printed format was undermined by GIS technologies and online data delivery, while the 2D-model concept has been eroded by technologically advanced modelling technologies, and long-term mapping programmes are challenged by cost-efficient thematic and targeted field strategies.

However, the fundamental drawback of the traditional map format and related mapping procedure may be none of these, but the conceptual limitations and, especially, the narrow data model specifications. Geology consists of several subtopics, such as petrology, structural geology, stratigraphy and metamorphic geology, and all these utilize the spatial representation of data and interpretations. Any map with a scale, layout and legend has resolution limitations, both in the amount of detail and overlapping map features. The cornerstone of the shifted paradigm is no longer a printed one-layout map series but efficient storage of accessible versatile map information – the system. A modern map data architecture allows different approaches (e.g. tectonic, stratigraphic, structural) via a theme-layer-based structure. As a result, the geological features can be stored in all the richness provided by the alternative approaches. The combined use of the map themes enables a complete view of all aspects of the up-to-date regional geology.

The role of a modern Geological Survey

The transition from 2D to 3D modelling of geology needs to be supported, both within the Geological Survey of Finland (GTK) and nationally, by an efficient infrastructure. In the future, one key function of GTK will be to provide reliable geological spatial data and interpretation for various application areas, such as mineral potential assessment and infrastructure planning. In any forward modelling process, the consistency, standardization and traceability of the input map data are of crucial importance.

In practice, the transformation from map sheets to data architectures is a tedious process. The planning and maintenance of the system is not possible without a truly systemic approach with common rules, defined terms and harmonization of the legacy information – including maps with variable classification systems. Positively, generic conceptual models, such as the North American Data Model (NADM-C1), the international collaboration coordinated by the Commission for the Management and Application of Geoscience Information (CGI of IUGS), together with key technologies, such as globally shared widget-based vocabularies hosted by the ARDC (Australia), offer unseen opportunities for geological data infrastructures. In this vision, the role of geological survey organizations is to create a national-level information strategy, arrange the vast legacy data and enable the interoperability of systems according to the internationally developing overall frame. This mission is driven and enabled by technological change, but it is important to see that the work cannot be constrained by technologies – it must be based on the needs of the developing science and different branches of geology.

4 Geological Survey of Finland, Bulletin 412 Editors’ preface

Geological mapping in Finland The regional geology programmes in Finland have been very long term, and their development consists more of stepwise evolution than revolutionary changes driven by new technologies. However, in some cases, too slow evolution has led to the extinction and termination of mapping programmes. GTK has carried out geological mapping in Finland for more than 100 years. Since the 1980s, all of the bedrock observations have been stored in a GTK database, and since the 1990s, the GIS approach has shown the way to fully digital mapping processes. The map sheet-based approach was replaced in 2005 by a seamless bedrock map database, which has been further developed towards a system of nationwide thematic layers compatible with the (IUGS- CGI-GeoSciML) standards. The superficial (Quaternary geology) mapping process was completely reformed following access to LiDAR imagery. The mapping programme was replaced by modern glacial terrain mapping, which was conceptually influenced by the glacial dynamics of the Fen- noscandian ice sheet. The extensive GTK databases and the modern information infrastructure provide a good work environment for regional interpretation. During the last 10 years, modelling technologies have emerged, and 3D is gradually becoming the mainstream in the depiction and conceptualization of geology. As a next step forward, GTK started preparation for a National Geological Framework of Finland (NGFF) in 2017. This volume presents some of the key results.

The contributions The authors of the first paper started working with GIS and GTK information systems in the 1990s and have experienced the technological change since then. Their contribution, “GTK Map Data Architecture: the core of the developing National Geological Framework of Finland” (Ahtonen et al.), is the latest ring in the long chain of development measures. The paper describes the current status of the GTK Map Data Architecture (MDA) and also connects it to a broader national context. The selected approach aims to link the spatial features, systematic classification systems and the primary scientific content. The MDA is designed to enable easy access to different kinds of structured geological information, and it will be versatile in fulfilling the needs of the various user groups.

The second paper, “Classification of regional-scale tectonic map units in Finland” (Kohonen et al.), builds on the authors’ experience in national-scale geological compilations, tectonic modelling and map data management. The paper provides a new classification system for tectonic-scale map units in Finland. The authors propose two new province categories (crustal province, structural province) and redefine the concept of tectonic province. The work is closed by a discussion on the relationships between the novel classification system, tectonic terminology and time-stratigraphy in Finland.

“Major thrusts and thrust-bounded geological units in Finland: a tectonostratigraphic approach”, the third paper by Luukas & Kohonen, applies the structural province division of the previous paper and summarizes our current knowledge of thrust systems in Finland. The authors define new bedrock map units bounded by major thrusts and discuss their significance in understanding geological relationships and features presented in regional and national map compilations.

The fourth paper, “Classification system for superficial (Quaternary) geological units in Finland” (Palmu et al.), presents the views of the leading GTK experts on the applicability of different classification systems to Quaternary deposits. The authors propose a new glacial dynamic (GD) map unit division and clarify the use of morpho-lithogenetic (MLG) classification in Finland. The GD approach creates an overall framework for depositional models, whereas the MLG system is found useful in the interpretation of LiDAR DEM data. These systems, combined with the classic stratigraphy, cover the needs of both regional superficial mapping and more detailed Quaternary research on vertical sections.

The work presented in this volume is part of the GTK programme ‘3DSuomi / National Geological Framework of Finland’ (GTK project number 50402-20104). Jarmo Kohonen planned and coordinated the compilation of this volume and took care for the overall terminological consistency of the articles. Timo Tarvainen was responsible for the review process of all the four articles. We express our warmest thanks and appreciation to the referees for sharing their expertise and precious time. Roy Siddall is thanked for revising the language. Päivi Kuikka-Niemi provided valuable assistance as the technical editor of the volume.

Espoo, 22.2.2021

Jarmo Kohonen and Timo Tarvainen Editors of this GTK Bulletin

5 Geological Survey of Finland, Bulletin 412 Jarmo Kohonen and Timo Tarvainen

6 Developments in map data management and geological unit nomenclature in Finland Edited by Jarmo Kohonen and Timo Tarvainen Geological Survey of Finland, Bulletin 412, 7–32, 2021

GTK MAP DATA ARCHITECTURE: THE CORE OF THE DEVELOPING NATIONAL GEOLOGICAL FRAMEWORK OF FINLAND

Niina Ahtonen2), Jarmo Kohonen1*), Jouni Luukas2), Antti E. K. Ojala1), Jukka-Pekka Palmu1) and Jouni Vuollo3)

Ahtonen, N., Kohonen, J., Luukas, J., Ojala, A. E. K., Palmu, J.-P. & Vuollo, J. 2021. GTK Map Data Architecture: the core of the developing National Geological Framework of Finland. Geological Survey of Finland, Bulletin 412, 7-32, 7 figures and 2 appendices.

The ongoing transition from 2D to 3D modelling of geology needs to be supported, both within the Geological Survey of Finland (GTK) and nationally, by efficient infrastructure. As a part of the future-forward national information infrastructure, the key performance of the GTK Map Data Architecture is to provide easy use of geological map data in all forward modelling processes. In practice, this means consistency, standardization and traceability of the available interpreted map data.

The implementation of the GTK Map Data Architecture (MDA) has two major objectives. First, on a practical level, the utilization and re-use of map data will be improved through a systematic, conceptually solid and standard-based national storage system. International standards and vocabularies will be applied in the construction of the MDA, and the NADM- C1 conceptual model and GeoSciML documentation are used as primary references. Second, a deeper-level objective is an information system enabling the management of geological content in full scientific depth, including both the underpinning conceptual framework and the original research behind the interpreted geological map data.

The GTK Map Data Architecture is designed to meet the needs of various use cases, such as 3D-modeling processes and GTK’s online map data services. The MDA concept is broader than a map library, and it is founded on three pillars: (1) structured spatial data, with the map objects and related attributes arranged as thematic layers; (2) structured non-spatial data, including the Finstrati databases with definitions and descriptions of geological units and the Finstruct database with descriptions of the major geological structures, and (3) linked documentation, including key references with the original descriptions and scientific content.

The GTK Map Data Architecture is planned to be a dynamically developing part of the broader National Geological Framework of Finland. The GTK MDA combines the spatial features and systematic classification of the defined geological units and structures. Structured non- spatial data is the key element of the architecture and will link the regional spatial data to the key scientific references. The GTK MDA aims to enable access to geological information, not only to spatial map objects and their attributes.

Keywords: Geological map, map data architecture, spatial, 3D modelling, data model, Geological Survey, Finland

7 Geological Survey of Finland, Bulletin 412 Niina Ahtonen, Jarmo Kohonen, Jouni Luukas, Antti E. K. Ojala, Jukka-Pekka Palmu and Jouni Vuollo

1) Geological Survey of Finland, P.O. Box 96, FI-02151 Espoo, Finland 2) Geological Survey of Finland, P.O. Box 1237, FI-70211 Kuopio, Finland 3) Geological Survey of Finland, P.O. Box 77, FI-96101 Rovaniemi, Finland

* Corresponding author, e-mail: [email protected]

https://doi.org/10.30440/bt412.1

Editorial handling by Timo Tarvainen. Received 15.9.2020; Received in revised form 4.2.2021; Accepted 10.2.2021

8 Geological Survey of Finland, Bulletin 412 GTK Map Data Architecture: the core of the developing National Geological Framework of Finland

CONTENTS

1 INTRODUCTION...... 10 1.1 Perspective and rationale...... 10 1.2 GTK mapping tradition and legacy information...... 11 1.3 GTK Map Data Architecture as part of the National Geological Framework of Finland...... 11

2 GTK MAP DATA ARCHITECTURE...... 13 2.1 Conceptual framework...... 13 2.2 GTK approach ...... 15

3 STRUCTURED MAP DATA...... 17 3.1 GTK Map Database: structured spatial data...... 17 3.2 Finstrati and Finstruct: structured non-spatial data...... 19

4 CONCLUDING REMARKS ...... 19

ACKNOWLEDGEMENTS...... 20

LIST OF APPENDICES ...... 20

REFERENCES ...... 21

APPENDIX 1...... 22

APPENDIX 2 ...... 28

9 Geological Survey of Finland, Bulletin 412 Niina Ahtonen, Jarmo Kohonen, Jouni Luukas, Antti E. K. Ojala, Jukka-Pekka Palmu and Jouni Vuollo

1 INTRODUCTION

1.1 Perspective and rationale

The Geological Survey organizations (GSOs) all over • Modular map datasets with scientifically sound the world have had to develop governance frame- themes as a basis of the data products works and structured data management systems to • Evolution from a simplistic 2D map portrayal to meet their objectives as modern information pro- more realistic 3D models viders. The fundamental importance of a shared conceptual frame was recognized by the North Our overall objective is to design and implement American surveys and lead to data-model standard a comprehensive system for storing geological NADM-C1 (NADMSC 2004) for the description of descriptions, particularly those related to geological geologic features in digital geologic map databases. maps (e.g., geological units, lithology and geologic The next challenge was set by the interoperability structures), as well as spatial information on map and the derived essence of standards. Australia has features. The main 2D realization is the national been the beacon showing the way to implementa- geological map dataset with various derived prod- tion of standards to geological information systems. ucts and online services. The Geological Survey of Finland (GTK) has cre- During the last decade, 3D modelling and map- ated a vision and a national approach for the pro- ping has emerged and is now gradually becoming duction and storage of, as well as services for all the mainstream in the description and portrayal of primary and interpreted geological information. geology. In 2017, GTK started to prepare a long- System development has been ongoing for several term programme (‘3DSuomi’; Kohonen et al. 2019), years. The present contribution outlines GTK’s Map which aims to facilitate the overall transition from Data Architecture (MDA) and the concepts under- the 2D approach to 3D in all activities, from geo- pinning the system. The fundamental idea is that logical data collection and interpretation to the the GTK MDA will have the capability to develop production of digital outputs and services. Easy towards a more advanced geological information access to well-organized geological map data is an architecture with scientific geological content as the essential requirement for an efficient 3D modelling main focus, not only the storage of spatial data. process. The main input to 3D modelling systems GTK MDA forms an essential part of the developing consists of primary constraints (data) and second- National Geological Framework of Finland (NGFF). ary constraints (interpreted data). GTK map data As an overall objective, the NGFF shares features (interpreted 2D data), 2D data models and GIS of the BRGM RGF program (Urvois et al. 2016) and technology lay in practise the foundation for geo- the systems implemented by Geoscience Australia logical 3D modelling. Explicit geological 3D mod- (https://www.ga.gov.au/about/projects/resources/ els are typically directly derived from 2D maps and continental-geology) and many other GSOs. cross-sections, and the reliability of the implicit 3D A geological map compilation is currently not models largely depends on the quality of the input only the final product of an interpretation process, data. Improvement of the quality of structured 2D but also provides essential input data for forward data is a foremost task of the 3DSuomi programme. modelling processes. Typically, the derived outputs This paper provides an overview of GTK’s include generalized and thematic maps, GIS-based approach to geological information manage- spatial analyses (e.g. Nykänen & Ojala 2007) and ment and describes: (1) the Map Data Architecture geological 3D models (see Kohonen et al. 2019). (MDA) as a part of the evolving National Geological Information technology and advances in geological Framework of Finland (NGFF), (2) the overall struc- conceptual modelling have opened up new perspec- ture and functionality of the MDA. Map theme tives and approaches in the management of map descriptions can be found in the appendices, but data: technical description, like database structures • National geological compilations at various scales and feature class relationships diagrams are not • Recurrently updated, ‘evergreen’ map included. compilations

10 Geological Survey of Finland, Bulletin 412 GTK Map Data Architecture: the core of the developing National Geological Framework of Finland

1.2 GTK mapping tradition and legacy information

GTK has systematically mapped the geology and Earth The stepwise evolution path of the long-term resources of Finland for well over 100 years. The geol- regional mapping programmes of GTK includes ogy of Finland is characterized by Precambrian crys- some major milestones, for example: talline bedrock (Fennoscandian Shield) covered by a • Since the 1980s, all the bedrock field observations thin layer of Late Quaternary superficial deposits. The have been stored in a GTK database distinctly two-fold characteristics of Finnish geology • Since the 1990s, the GIS implementation has are directly reflected in the mapping practices and resulted in fully digital mapping and map pro- research traditions in Finland. duction processes The limitations of traditional lithostratigraphic • In 2005, the map sheet-based approach was methods in meeting the needs of both Precambrian replaced by seamless map databases and Quaternary geology are widely recognized (cf. • Since 2008, in (Precambrian) bedrock map- NACSN 2005), and the strong lithology-based ping, the lithology (rock type)-based procedure mapping tradition in Finland can be seen as a con- has been progressively replaced by a geological sequence of this. The Precambrian terrain has tra- unit-based method; introduction of the Finstrati ditionally been mapped according to the rock types concept. of different age groups, and the Quaternary uncon- • Since 2016, the superficial (Quaternary) geology solidated deposits have been divided to classes by mapping process has been completely renewed the sediment type and the grain size class. In 2008, following the emergence of LiDAR imagery GTK bedrock mapping was directed towards a unit- • In 2018, construction of the Finstruct database based (litostratigraphic-lithodemic) approach, and and linked structural and tectonic map themes as a result, a seamless 1:200 000 scale bedrock com- (bedrock) was started pilation with a linked non-spatial unit database The amount of GTK legacy information is vast, (Finstrati) was established in 2009 (see Luukas et and a major part of this has been digitized and uti- al. 2017). Mapping of superficial deposits by GTK lized in the production of the current core data, such followed this example a couple of years later, and as the MDA map themes. These data are a major a new database for Quaternary map units has been asset for GTK, but consistency, metadata and data defined (Palmu et al. 2021; this volume). access still need improvement. GTK’s field map- The division of geological units is essential in ping activities have considerably declined during order to understand the geometry and sequence of the last ten years, but the extensive GTK databases rock bodies. Such an approach has many advantages combined with a modern information infrastruc- regarding both the arrangement of the geological ture provide an applicable and informative working content and technical aspects (such as database environment for novel geological interpretations structures). The original Finstrati has been reviewed and an excellent starting point for targeted field and divided to FinstratiKP for the Precambrian units operations. and FinstratiMP for the Quaternary units.

1.3 GTK Map Data Architecture as part of the National Geological Framework of Finland

Within the overall 3DSuomi frame, the National geology (e.g., tectonics, mineral systems, engi- Geological Framework of Finland (NGFF) means neering geology) by applying the National Data the harmonization, 3D extension and consolidation Architecture of the GTK information infrastructure (Fig. 1). • Provide a national reference and spatial 3D The overall objectives of the NGFF cover all framework aspects of the GTK mission. In short, the NGFF is • Provide a technology architecture, including 3D the conceptual and technical framework for geo- software and 3D data storage solutions needed logical research in 2D and 3D. Ideally, the NGFF for the implementation of 3DSuomi will be able to: • Activate innovative new applications, interpreta- • Accommodate 2D and 3D models of different tions and 2D and 3D models extents and scales representing various themes of

11 Geological Survey of Finland, Bulletin 412 Niina Ahtonen, Jarmo Kohonen, Jouni Luukas, Antti E. K. Ojala, Jukka-Pekka Palmu and Jouni Vuollo

JK 0709_2020 National Geological Framework of Finland: an outline

Stratigraphic Guides (SSK collaboration) Classifications etc. Vocabularies etc. ’3D-Suomi Domain’ GEOLOGICAL CONCEPTS > Finstrati concept ’Geological 2D data models’ ’Geological 3D data models’ Regional Geology -2D core themes Regional 3D models -2D generalized theme sets Crustal scale model REALIZATIONS > Topical 2D themes Deposit models etc.

Applied 2D themes Urban area models Engineering geology models GTK GIS systems 3D-software architecture SYSTEMS > Finstrati database GTK Online service systems 3D data storage

Fig. 1. A schematic diagram of the 2D to 3D transformation at GTK. The 3D realizations (models) build on 2D map data. Solid geological data models with supporting scientific documentation and robust technical systems form the framework for 3D modelling.

The NGFF Data Architecture is based on defined holding and maintaining geological data in Finland. concepts, data models, vocabularies and interna- The GTK Business Architecture (processes and tional standards. Such an information system for all services) is in continuous interaction with the corporate data, including primary and interpreted Data Architecture, which in turn is supported by 2D and 3D presentations and models, would ide- Application and Technology Architectures. The ally increase both the efficiency of processes and the NGFF Data Architecture consists of components that quality of the end products in all activities, including are essential for 2D and 3D data production and contracted projects and customer solutions, mapping forms a subset of the entire GTK Data Architecture processes and scientific interpretations. At the same (Fig. 2). This paper focuses on the GTK Map Data time, a well-organized and well-structured database Architecture (see Fig. 3), which currently, by volume would be a major asset for the long-term relevance at least, forms the core part of the developing NGFF of GTK as a science-based agency and an authority data architecture.

GTK Data Architecture

NGFF Data Architecture • Map Data Architecture (MDA) MDA supporting 2D > 3D transition • 3D Data Architecture • Other components NGFF enabling 3D-modelling in GTK NGFF Application Architecture

NGFF Technology Architecture

Fig. 2. NGFF domains essential for the implementation of an appropriate corporate-level 3D work process at GTK.

12 Geological Survey of Finland, Bulletin 412 GTK Map Data Architecture: the core of the developing National Geological Framework of Finland

The National Geological Framework of Finland an integrated basis for various types of geological is a long-term objective: a structured information interpretation and applications, and (4) the frame- system and technology platform providing tools work should have capabilities to guide future geo- for efficient access to both primary data and inter- scientific research. pretations. The general requirements for the NGFF The implementation and management of an are condensed to the following points: (1) the data enterprise-scalable Map Data Architecture requires models must be nationally relevant and compat- clear business rules for data security, ownership, ible with international standards, (2) the framework and authority for all data that is stored in data- must be capable of accommodating various geo- bases. Integration of data from different sources logical themes, such as tectonic modelling, aqui- will require the maintenance of adequate metadata fer modelling and mineral systems modelling, (3) such that the original source for each data object the fundamental, nationwide models must act as can be determined and traced.

PHASE 1 • Conceptual modelling • Definition of the overall (spatial) data architecture (structure of the information infrastructure) PHASE 2 • Definition of the spatial data themes (main feature classes) • Linked datasets (e.g. Geological Units) • Outline of the application architecture (e.g. software and database solutions) • Implementation of the 2D architecture PHASE 3 • Integration into international data services • Implementation of the 3D architecture IN ALL PHASES • Strategic planning • Project planning • Application of standards and international guidelines • Training programmes • New and updated data products and online services

Fig. 3. A schematic diagram of NGFF implementation.

2 GTK MAP DATA ARCHITECTURE

2.1 Conceptual framework

All geological information, including geological ing geological features defined by the specific main units, is based on primary data (e.g., observations, descriptor, such as ‘rock type name’, ‘lithostrati- measurements) and interpreted spatial features graphic unit name’, ‘tectonic province name’ or (e.g., geological unit boundaries, structures) with ‘fault type’ (Fig. 4). It is essential to see the distinc- documented scientific descriptions, such as reports tion between map data and their cartographic map and articles. However, all the map features and geo- symbolization. Map data are geological features in logical depictions are eventually abstract concep- a real-world spatial reference framework whereas tions managed by conceptual modelling. The maps cartographic map results in symbolization of those and models consist of geometric objects represent- via coloured areas, lines and map symbols.

13 Geological Survey of Finland, Bulletin 412 Niina Ahtonen, Jarmo Kohonen, Jouni Luukas, Antti E. K. Ojala, Jukka-Pekka Palmu and Jouni Vuollo

Cartography: -Map symbol libraries -Colour charts -etc.

DATA MODEL WHERE Geological Occurrence: Concepts: WHAT Spatial units and -Stratigraphic Principles Descriptors: object geometry -Classification Systems (Map Legends) -Polygons / 3D objects -Vocabularies (Model Feature Catalogs) -Lines -Stratigraphic Units -Points -Provinces -Rock type classes -Structural feature classes -etc.

Fig. 4. Simplified representation of the generic data model for geological maps and models. The presence of an object is described by 1) its spatial features and 2) its properties with a defined set ofdescriptors . (Diagram modified after Soller et al. 2005)

The conceptual level consistency, concepts asso- Thus, one major challenge is to compose data mod- ciated with defined terms, form the fundamental els that are suitable for legacy data management, basement of a sustainable information infrastruc- but also have flexibility for extension with new ture. Whitehead et al. (2010) noted: ‘Geoscience data schemas that allow the map compiler to represent capture is expensive. In order to extract maximum value, what is actually known about the geological features the data need to be consistently described, easily found, portrayed on a geological map. and then shared among those who need it. While storage Our intention is to apply the international best and transfer standards are vital, they lack a descriptive practices and standards wherever possible. The element which standardizes the meaning of their con- major underlying framework is the NADM-C1 contents.’ Without tackling the ontological challenge ceptual model (NADMSC 2004). The model empha- as such, careful conceptual modelling is one key sizes geoscience concepts and relationships related to long-term functionality and versatility of the to information presented on geological maps, and architecture. the model documentation (https://pubs.usgs.gov/ The vital interaction between the advancing sci- of/2004/1334/) states: ‘A key aspect of the model is ence (new theories and concepts) and information the notion that representation of the conceptual frame- technology now provide unforeseen opportunities work (ontology) that underlies geologic map data must to develop completely new insights into geologi- be part of the model, because this framework changes cal mapping and modelling. Unfortunately, the with time and understanding, and varies between systemic advantage of these extensions to tradi- information providers. The top level of the model dis- tional geological map content is not automatically tinguishes geologic concepts, geologic representation accepted by all members of the community (see concepts, and metadata. The geologic representation USGS NCGMP 2020) or gaining funds for long-term part of the model provides a framework for representing information infrastructure programs. A report by the ontology that underlies geologic map data through NADM-SLTT (2004) elegantly describes the deep- a controlled vocabulary, and for establishing the rela- seated tension between ‘traditionalistic, legacy ori- tionships between this vocabulary and a geologic map ented’ and ‘maximum scientific content oriented’ visualization or portrayal.’ philosophies in geological map data management.

14 Geological Survey of Finland, Bulletin 412 GTK Map Data Architecture: the core of the developing National Geological Framework of Finland

2.2 GTK approach

The arrangement of geological map data is not GIS technologies, but the ideal solutions for the just a practical task. It is based on a long mapping future still need to be carefully considered. With tradition and national conventions developed over geological data, the ultimate relational database decades. Nationwide geological maps are essential implementations may lead to very complex data- components of a geoscientific framework. GTK has a base structures and result in a lack of agility in both long history of compiling 1:1M scale geological maps database development and applications. In contrast, (e.g. Simonen 1980, Korsman et al. 1997, Nironen et pure GIS solutions may lead to simplistic data modal. 2016, Niemelä et al. 1993) and their national leg- els and poor query performance. The management ends. However, the conceptual frame of a national of different scales of map data without duplication map information system is no longer a solitary map of the attribute data is also found as a challenge. compilation or a national legend template. Instead, The GTK Map Data Architecture is planned to the core of the geological framework is the Map be a dynamically developing system of geological Data Architecture with defined data models, clas- information (see Fig. 5), and is basically founded sification systems and linked vocabularies. The on three pillars: NADM-C1 specifies the basic types of geological (1) Structured spatial data: map objects and related features, with guidelines for descriptors. It does attributes not specify a database implementation. We apply (2) Structured non-spatial data: Finstrati databases the NADM-C1 geological concepts hierarchy with with geological unit definitions and descrip- related classification systems and vocabularies to tions; the Finstruct database with major struc- define the descriptors, which direct the division of ture descriptions; related documentation; linked the spatial objects of a map or 3D model. to two other pillars Another key question in MDA construction is the (3) Key references with the original descriptions selection of technology. GTK has experience and a and scientific content long history of combining relational database and

’CONCEPTUAL WORKSHOP’ • Map themes vs. NADM-C1 major concepts • Geological concepts; GeoSciML; other standards • Data derived vs. interpreted map themes • Finstrati; map unit classification systems • Master Data vs. Compilations / Products • Other map feature classification systems

STRUCTURED MAP DATA LINKED DOCUMENTS

Structured Spatial Structured Non-spatial Data Data

• GTK GIS applications • Finstrati database applications • HTML links • Geodatabase • Finstruct and other applications • URI-based document identifiers and services • Other database solutions • Etc. • XML based technologies • Etc. ’TECHNOLOGY WORKSHOP’

Fig. 5. The main components of the GTK Map Data Architecture (blue boxes). The architecture has been designed according to the selected concepts, definitions and geological data models by the ‘Conceptual Workshop’. The functionality relies on applications and technologies selected by the ‘Technology Workshop’.

15 Geological Survey of Finland, Bulletin 412 Niina Ahtonen, Jarmo Kohonen, Jouni Luukas, Antti E. K. Ojala, Jukka-Pekka Palmu and Jouni Vuollo

The selected approach aims to combine the spa- utes for different spatial scale compilations, and the tial features and systematic classification of the second utilizes the traditional scalable classifica- defined geological units with the primary descriptions (e.g., group – formation – member – bed). tion and geological interpretation. The structured Most importantly, the integrity of the structured non-spatial data form the scientific key element non-spatial core data is sustainable compared to of the architecture. For example, the conceptual data stored in numerous attribute tables. The linked division of different geological units, their char- non-spatial databases allow basic queries from GIS- acteristics and attributes form the backbone of the based services. Finstrati databases. These structured non-spatial All the structured map data are quality controlled data link the spatial master data (spatial objects) and maintained by GTK; the appropriate metadata to the key references (Fig. 6). Basically, the system is the most essential component of documentation. allows browsing from the map view to the unit lexi- Some of the linked documents, such as data mod- con (Finstrati) and further to the original scientific els, database descriptions and map theme feature reference source and, in the future, also vice versa. catalogues, are also produced and updated by GTK The architecture enables access to geological infor- (see Fig. 6). In addition to maintaining geological mation, not only to ‘map data’. information, the GTK Map Data Architecture is an The scalability is one of the major challenges in essential component of GTK’s ongoing data pro- all map data applications. The selected approach duction processes and services. New map data are described above provides two significant advan- generated in research projects or received from tages: (1) intelligent linkage of structured non- external sources (e.g., academia, companies). The spatial data (shared attributes between different project map library is the primary storage for these spatial scales and between 2D and 3D models) and outputs, and after a harmonization process, the data (2) maximal hierarchy of the non-spatial classifica- are incorporated into the structured GTK map data- tion systems. The first reduces duplication of attrib- base (Fig. 7).

JK 0909 2020

STRUCTURED MAP DATA LINKED DOCUMENTS

< ------Maintained and updated by GTK ------>

Structured Spatial Data Structured Non-spatial Data NGFF documentation Research Reports (static) • NGFF overall structure • Unit type section or type • GTK MDA description area -Map Theme feature catalogues • Unit definitions ’GTK map database’ Finstrati (geol_unit register) -Finstrati/Finstruct description • Descriptions of units and • Bedrock Map Themes • Stratigraphic units • GTK data models structures • Superficial Map Themes • Lithostratigraphic • GTK vocabularies (linked to CGI • Regional reviews and • Lithodemic terms) descriptions Both categories divided into • Tectonostratigraphic Internationally maintained • Core Themes • Allostratigraphic Key references linking primary documentation: • Generalized Themes • Other geological units • IUGS/CGI Standards research to Finstrati and to • Topical Themes • Lithotectonic -GeoSciML/ERML Finstruct • Applied Themes • Morpho-lithogenetic • Other standards • IUGS/CGI vocabularies All themes defined by Finstruct (struct_name register): • NADM-C1 • Feature classes with • Shear / fault zones • Stratigraphic Codes/Guides • Attributes • Major faults • Attribute value lists • Other major structures

Units linked to Finstrati Core of the MDA with links both to Structures linked to Finstruct the structured spatial data and to the key references (and other linked documents)

Fig. 6. The overall structure of the GTK Map Data Architecture. Finstrati and Finstruct link the spatial map units to the primary research reports. The consistency of the system is supported by NGFF documentation and international standards. The structure allows extensions from 2D map themes to 3D models without any major modification.

16 Geological Survey of Finland, Bulletin 412 GTK Map Data Architecture: the core of the developing National Geological Framework of Finland

External Data Sources / GTK Research Projects / GTK Legacy Data

Unit/Structure definitions Map Data Reports and descriptions

Project Map Library

Harmonization Structured Spatial Master Structured Non-spatial Data Linked Documents Data Compilation Forward modelling Generalized Thematic Models Map Data Map Data

GTK products and online services

Fig. 7. The GTK Map Data Architecture (blue boxes) is positioned between data input (top) and the GTK customer interface (bottom).

3 STRUCTURED MAP DATA

Structured map data refers to thematically and data). The system supports easy access and the hierarchically arranged datasets with defined fea- orderly use of map data in any forward modelling tures and controlled vocabularies. Structured map process and enables defined update procedures for data comprise the GTK Map Database (spatial data) all parts of the system. and Finstrati and Finstruct databases (non-spatial

3.1 GTK Map Database: structured spatial data

The GTK Map Database is a structured system for linked to the non-spatial databases. The master the interpreted spatial 2D information. The attrib- data are the primary source for modelling processes ute data are stored in theme-specific GIS attribute and generalized or thematic map compilations. tables. All the attribute value lists are composed Basically, structured spatial data are not limited to according to internationally recognized classifica- 2D map data. A major part of the interpreted map tion systems with some national modifications (e.g. data is used as input data in 3D modelling and, con- rock name value lists as part of the system docu- sequently, the models have close ties to the spatial mentation). The key attributes link map features map data and to the related attributes. In the future, (geological units and the major structures) to the the 3D spatial objects can be incorporated as part of Finstrati and Finstruct databases. the system by an extension or as a separate system Structured spatial master data (Core Themes; linked to the GTK MDA. see Fig. 6) are the first-generation harmonized, Bedrock geology and superficial geology form structured map data arranged as thematic layers the main branches of the GTK Map Database. The according to the main feature classes derived from map themes of both branches are divided into core the NADM-C1 conceptual model. The master data themes and other themes. A more detailed descrip- are regularly updated by the harmonization of new tion of the GTK Map Database can be found in the map data gathered in the project map library (Fig. Appendices, but the components are summarized 7), ensuring and checking that map features are as follows:

17 Geological Survey of Finland, Bulletin 412 Niina Ahtonen, Jarmo Kohonen, Jouni Luukas, Antti E. K. Ojala, Jukka-Pekka Palmu and Jouni Vuollo

Core Themes (Regional geology master data) The NADM-C1 top-level geological classes • ‘Evergreen’ thematic compilations with a regular (Geological Unit, Earth Material and Geological update procedure by GTK Structure) form the main frame for the concep- – New data from project maps (harmonization) tual modelling of the GTK master map data. The – Primary update to the core theme (not to gen- core themes with the underpinning regional geology eralized themes or digital products) conceptual model form the cornerstone of the sys- • Spatial map data in full resolution (not general- tematic production and storage of the (interpreted) ized to any nominal map scale) map data by GTK. The objective of the core theme • New feature classes and features added with definition was to create a map database with (1) developing science and the conceptual model a science-based thematic division, (2) minimum Generalized themes overlap between the themes and (3) appropri- • Selected set of core themes generalized for the ate options for extension with a minimum risk of production of digital or printed map products conceptual-level inconsistencies. with lay-out and map symbols Topical and applied themes are linked on concep- • Generalized regional data are widely used in the tual level to the GTK regional geology model and the creation of research report figures and as the shared features are identical. The geological data background of thematic map compilations model and corresponding feature catalogues are Topical themes extended by features specific to the topic (Fig. 8). • Themes displaying scientific interpretation (e.g. The feature catalogues for solitary maps (e.g., pro- regional variation of metamorphic grade) ject maps) are also supported by the GTK geologi- • Data usage with reference to compilers only cal data models and map theme feature catalogues. Applied themes The use of identical features is recommended to • Themes related to applied geology (e.g. engineer- support the incremental update of the core themes. ing geology, aggregates) In principle, the configuration of the map theme

JK 0909 2020

NADM-C1 GeologicConcept

GTK Regional Geology Regional Geology GTK Regional Geology Conceptual Model Core Themes Feature Catalogues

GTK Application Area 1 GTK Applied Theme Applied Theme Conceptual Model Feature Catalogue GTK Application Area 2 GTK Applied Theme Applied Theme Conceptual Model Feature Catalogue GTK Application Area 3 GTK Applied Theme Applied Theme Conceptual Model Feature Catalogue

Fig. 8. Conceptual-level consistency is a major requirement for structured spatial data. International compliance is supported by linking the GTK regional geology conceptual model to NADM-C1. The consistency of the GTK Map Database is based on a harmonized system of all the conceptual-level models. As a result, the feature catalogues of the applied and topical themes (lower right in the diagram) form an extendable system with the basic conceptual framework inherited from the generic conceptual models.

18 Geological Survey of Finland, Bulletin 412 GTK Map Data Architecture: the core of the developing National Geological Framework of Finland follows the same steps as the process for a solitary • Generation of the map theme feature catalogue map or model: (main feature classes, features) • Map theme definition with theme-specific fea- • Terminological definition of the features and tures (descriptors derived from the conceptual related attributes (mainly by links to CGI / model) INSPIRE vocabularies) • Connection of the features to the spatial objects • Compilation (or checking) of attribute value lists (e.g., polygons, lines). used by GTK

3.2 Finstrati and Finstruct: structured non-spatial data

In a traditional GIS approach, the attributes char- ponent of the structured non-spatial data. Spatially acterize the spatial geometric objects. In the GTK it is confined by the parent unit, and the description MDA the non-spatial data together with key refer- can be found in the original reference. Currently ences address the geological ideas underpinning the the MDA structured non-spatial data consist of the spatial objects. The linked but solitary non-spatial following parts: database (see Fig. 6) extends the MDA to a digital • Non-spatial unit databases lexicon and to management of geological units and – FinstratiKP (Bedrock geology unit database) structures. These features are defined and named – Stratigraphic units as a result of geological research, and the link to – Lithostratigraphic units key references is therefore an essential part of their – Lithodemic units management. – Lithotectonic Units The geological units and structures comprising – Tectonic-scale units Finstrati and Finstruct, respectively, may be linked – Thrust-bounded units to an unlimited number of spatial objects (2D/3D; – FinstratiMP (Superficial geology unit database) surface/subsurface). Nonetheless, the geological – Stratigraphic units features are not only attributes of a polygon or line, – Lithostratigraphic Units but conceptual geological features basically inde- – Allostratigraphic Units pendent of object geometry. Therefore, the Finstrati – Morpho-lithogenetic Units units (and Finstruct structures) must not have a – Glacial Dynamic Provinces and Regions corresponding map object. For example, a defined – Finstruct (Bedrock structure database) lithostratigraphic member or bed may be too minute – Major (named) structures for any map scale in use, but it forms relevant com-

4 CONCLUDING REMARKS

Geology, as a science, is fundamentally based on geology), full coherence may not be a realistic concepts, models and theories. Geology is rich in objective except for the highest conceptual lev- terminology, and the AGI Glossary (Neuendorf et els. Nevertheless, many practical reasons call for al. 2005) has nearly 40 000 entries. As research increased conceptual consistency. The versatility of advances, our concepts are improved and modified. map data (and all interpreted data) will be improved This, together with developing information tech- when the different domains, such as scientific nologies, makes the systematic storage of geological research, regional geology and applied geology, information, including both legacy data and new share the same national or international system. observations, a highly challenging task. The coordinated system of thematic data sets (Data The fundamental importance of consistency at Themes) will ideally support this development at the conceptual level is widely understood, but as GTK and in Finland. The MDA improves the inter- concepts are developing within different branches operability of GTK data regarding both international of geology (e.g., mineral systems, engineering data infrastructures, such as INSPIRE (Cetl et al.

19 Geological Survey of Finland, Bulletin 412 Niina Ahtonen, Jarmo Kohonen, Jouni Luukas, Antti E. K. Ojala, Jukka-Pekka Palmu and Jouni Vuollo

2019), EGDI (www.europe-geology.eu) and more tion of spatial structural features will support both science-oriented Macrostrat (Peters et al. 2018). geological 3D modelling and the regional mapping Structured geological data, with definitions, hier- of different structural domains. archies and sufficient metadata, improve the quality The geological map has dominated the landscape of any forward modelling process, either in 2D or for more than 200 hundred years. The traditional 3D. Geological 3D modelling at various scales, and printed map, or geological 2D model of the region, especially implicit modelling, sets high require- obviously has a very limited capacity to depict all ments for the input data, including the interpreted the geological detail or the phenomena related to geological map data. The concrete benefits of the geological evolution. Furthermore, the technical MDA for 3D modelling include: (1) improved qual- limitations of the map (such as the defined scale ity control of 2D input data, (2) shared names and and use of symbols) have unfortunately reflected attributes in the MDA in 3D models, (3) scalability mapping specifications and regional geological data provided by the unit hierarchies and (4) the linkage models; in many cases, we have literally been ‘map- of the regional and applied models by conceptual- ping’, not collecting data for geological research in level consistency partly of the data models. all its richness. New technologies have fundamen- The trend is from qualitative description to quan- tally changed the situation, and our task is to utilize titative (or semi-quantitative) data sets. These this opportunity. The GTK Map Data Architecture types of attributes, such as rock density and modal is one step from the map-dominated (spatial, GIS composition, are of growing importance. Structural technology) approach towards content-oriented geology and structural data are developing together (conceptual, information systems) geology. with the modelling, and the systematic classifica-

ACKNOWLEDGEMENTS

The numerous discussions with our international and GTK colleagues are greatly appreciated. We are grateful to C. Loiselet and J. Virtasalo for their careful reviews.

LIST OF APPENDICES

The appendices are part of MDA documentation and will be updated on a regular basis.

Appendix 1 Structured spatial map data; Bedrock; map themes and main feature classes

Appendix 2 Structured spatial map data; Superficial deposits; map themes and main feature classes

20 Geological Survey of Finland, Bulletin 412 GTK Map Data Architecture: the core of the developing National Geological Framework of Finland

REFERENCES

Cetl, V., Tomas, R., Kotsev, A., de Lima, V. N., Smith, R. S. ternary deposits of Finland and northwestern part of & Jobst, M. 2019. Establishing Common Ground Russian Federation and their resources 1:1 000 000. Through INSPIRE: The Legally-Driven European Spa- Sheet 1 Western part. Geological Survey of Finland. tial Data Infrastructure. In: Service-Oriented Map- Available at: https://tupa.gtk.fi/kartta/erikoiskartta/ ping. Berlin, Germany: Springer, 63–84. ek_027.jpg Geoscience Australia. Australian Government. Available Nironen, M., Kousa, J., Luukas, J. & Lahtinen, R. (eds) at: https://www.ga.gov.au/about/projects/resources/ 2016. Geological Map of Finland: Bedrock 1:1 000 000. continental-geology [Accessed 02.02.2021] Geological Survey of Finland. Available at: http://tupa. Kohonen, J., Putkinen, N., Laine, E.-L., Ojala, A., Luukas, gtk.fi/kartta/erikoiskartta/ek_097_300dpi.pdf J. & Virtasalo, J. 2019. Geological Survey of Finland: Nykänen, V. & Ojala, V. J. 2007. Spatial Analysis Tech- steps from seamless mapping towards a national geo- niques as Successful Mineral-Potential Mapping logical 3D-framework. In: MacCormack, K. E., Berg, Tools for Orogenic Gold Deposits in the Northern R. C., Kessler, H., Russell, H. A. J. & Thorleifson, L. Fennoscandian Shield, Finland. Natural Resources H. (eds) Synopsis of Current Three-Dimensional Geo- Research volume 16, 85–92. Available at: https://doi. logical Mapping and Modelling in Geological Survey org/10.1007/s11053-007-9046-5 Organizations. Alberta Energy Regulator/ Alberta Palmu, J.-P., Ojala, A. E. K., Virtasalo, J., Putkinen, N., Geological Survey, AER/AGS, Special Report 112, 109– Kohonen, J. & Sarala, P. 2021. Classification system 117. Available at: https://ags.aer.ca/document/SPE/ of Superficial (Quaternary) Geologic Units in Finland. SPE_112_CH12.pdf In: Kohonen, J. & Tarvainen, T. (eds) Developments Korsman, K., Koistinen, T., Kohonen, J., Wennerström, in map data management and geological unit no- M., Ekdahl, E., Honkamo, M., Idman, H. & Pekkala, Y. menclature in Finland. Geological Survey of Finland, (eds) 1997. Suomen kallioperäkartta – Berggrundskar- Bulletin 412. (this volume). Available at: https://doi. ta över Finland – Bedrock map of Finland 1:1 000 000. org/10.30440/bt412.4 Geological Survey of Finland. Peters, S. E., Husson, J. M. & Czaplewski, J. 2018. Mac- Luukas, J., Kousa, J., Nironen, M. & Vuollo, J. 2017. Ma- rostrat: A platform for geological data integration jor stratigraphic units in the bedrock of Finland, and deep-time earth crust research. Geochemistry, and an approach to tectonostratigraphic division. Geophysics, Geosystems, 19, 1393–1409. Available at: In: Nironen, M. (ed.) Bedrock of Finland at the scale https://doi.org/10.1029/2018GC007467 1:1 000 000 – Major stratigraphic units, metamor- Simonen, A. 1980. Suomen kallioperä 1:1 000 000. Pre- phism and tectonic evolution. Geological Survey of Quaternary rocks of Finland. Finlands berggrund. Finland, Special Paper 60, 9-40. Available at: http:// Geological Survey of Finland. Available at: https:// tupa.gtk.fi/julkaisu/specialpaper/sp_060_pag- tupa.gtk.fi/kartta/erikoiskartta/ek_012.pdf es_009_040.pdf Soller, D. R., Berg, T. M. & Stamm, N. C. 2005. The Na- NACSN, North American Commission on Stratigraphic tional Geologic Map Database Project: Overview and Nomenclature, 2005. North American Stratigraphic Progress. U.S. Geological Survey, Open-File Re- Code. AAPG, Bulletin 89 (11), 1547–1591. Available at: port 2005-1428. Available at: https://pubs.usgs.gov/ https://ngmdb.usgs.gov/Info/NACSN/05_1547.pdf of/2005/1428/soller1/ NADM-SLTT, North American Geologic Map Data Mod- Urvois, M., Baudin, T., Cagnard, F., Calcagno, P., Chauvin, el Steering Committee Science Language Technical N. et al. 2016. The Spatial Data Infrastructure for the Team, 2004. Report on Progress to develop a North Geological Reference of France. 35th International American Science-Language Standard for Digital Geological Congress: IGC 2016, Aug 2016, Cape Town, Geologic-Map Databases. Digital Mapping Techniques South Africa. ffhal-01355390f. Available at: https:// ‘04, Proceedings. Available at: https://pubs.usgs.gov/ hal-brgm.archives-ouvertes.fr/hal-01355390 of/2004/1451/pdf/nadm.pdf USGS NCGMP, U.S. Geological Survey National Coopera- NADMSC, North American Geologic Map Data Model tive Geologic Mapping Program, 2020. GeMS (Geo- Steering Committee, 2004. NADM Conceptual Mod- logic Map Schema)—A standard format for the digital el 1.0 – A conceptual model for geologic map infor- publication of geologic maps. U.S. Geological Survey, mation. U.S. Geological Survey, Open-File Report Techniques and Methods, book 11, chap. B10. 74 p. 2004-1334. 58 p. Available at: http://pubs.usgs.gov/ Available at: https://doi.org//10.3133/tm11B10. of/2004/1334. Also published as Geo-logical Survey of Whitehead, B., Gahegan, M., Everett, M., Hills, S. & Canada, Open File 4737, 1 CD-ROM. Brodaric, B. 2010. Fostering the exchange of geosci- Neuendorf, K. K. E, Mehl, J. P. & Jackson, J. A. (eds) 2005. ence resources for knowledge exploration and dis- Glossary of geology. 5thEdition. Alexandria: American covery. 4th eResearch Australasia Conference, Gold Geological Institute. 779 p. Coast, Australia, Abstracts. Available at:https://www. Niemelä, J., Ekman, I. & Lukashov, A. (eds) 1993. Suomen researchgate.net/publication/234082781_Foster- ja Venäjän Federaation luoteisosan maaperä ja sen ing_the_exchange_of_geoscience_resources_for_ raaka-ainevarat 1:1 000 000. Lehti 1 Länsiosa. Qua- knowledge_exploration_and_discovery

21 Geological Survey of Finland, Bulletin 412 Niina Ahtonen, Jarmo Kohonen, Jouni Luukas, Antti E. K. Ojala, Jukka-Pekka Palmu and Jouni Vuollo

APPENDIX 1 15.9. 2020

STRUCTURED SPATIAL MAP DATA; BEDROCK; MAP THEMES AND MAIN FEATURE CLASSES

J. Kohonen & J. Luukas

1 GENERAL DESCRIPTION OF SPATIAL MASTER DATA (‘GTK Bedrock Map database’)

GTK Bedrock map database is part of the GTK Map ing to defined classification systems. The Core Data Architecture (see Ahtonen et al. 2021; this vol- Themes (spatial master data) and the linked non- ume). This document describes the current structure spatial databases (FinstratiKP, Finstruct) con- of the spatial bedrock map data (interpreted data): stitute Regional Master Data (bedrock), which is (1) the underpinning conceptual model, (2) the map maintained and updated on regular basis by GTK. features arranged according to Geologic Concept Regional Master Data form the source for both gen- hierarchy and (3) the division to map themes. eralized data sets and thematic data sets (Fig. 1). Key part of the system are the Core Themes. Core themes contain the map data structured accord-

Ver. 14.09 . 2020 BEDROCK Structural Regional Master Data interpretation -scale -Core themes (spatial) 3D interpretation Compilation Crustal -Linked databases (non-spatial) structures • Structural sequence * • Deformation phases

Core Theme KP_1M Scientific Metallogenic * Metallogeny Structure • Litho-units interpretation Structures Compilation Finstruct • Structures • Metallogenic provinces Formlines Major Structures DigiKP • Dyke swarms • Mineral potential estimates Description * Rakenneviivat + 200 update Core Themes Regular • Litho-units; main New Geological lithology Metamorphic Engineering Interpretation data generalization • Structures interpretation; Geology Map Units compilation* • Dyke swarms

• Bedrock properties Geological units Finstrati • Finstrati • Fracture zones Rock units Geological Units Description descriptions (.pdf) Metamorphic Applied Domains 1M Aggregates *no regular update by GTK • Mm isograds

• Rock type technical properties

Fig. 1. Diagram illustrating the vision for the functionality of the GTK Map Data Architecture (bedrock). The core of the system are Regional Master Data (spatial and non-spatial) regularly updated by GTK. Generalized theme sets (upper right) and the Topical / Applied themes (left and lower right) are also shown. (Green components are implemented, light green are progressing and red are in planning stage).

22 Geological Survey of Finland, Bulletin 412 GTK Map Data Architecture: the core of the developing National Geological Framework of Finland

2 CONCEPTUAL FRAMEWORK OF REGIONAL GEOLOGICAL DATA (bedrock)

The main feature classes are arranged according further arrangement of map features into thematic to NADM-C1 top-level Geologic Concept hierarchy layers called as ‘Map Themes’. (Fig. 1 and Table 1). The basic idea is to support the

Geologic Concept

1. Geologic Unit 2. Earth Material

Compound Lithostratigraphic Lithodemic Lithotectonic Mineral Unit Unit Unit Material 3. Geologic Structure Unconsolidated Rock Material Fold Fault Fracture Fabric Layering

Fig. 2. Diagram displaying the NADM-C1 top-level Geologic Concept hierarchy.

Table 1. The main feature classes used in GTK regional bedrock mapping arranged according to the NADM-C1 top level Geologic Concepts. Terms directly corresponding to NADM-C1 are indicated in grey.

1 Geologic Unit 2 Earth Material 3 Geologic Structure

1.1 Litostratigraphic unit 2.1 Compound material 3.1 Fold 2.1.1. Rock (rock type) 2.1.1.1 Weathered rock 2.1.1.1.1 Regolith/paleosol 2.1.1.1.2 Hydrothermally altered rock

1.2 Lithodemic unit 2.2 Mineral 3.2 Displacement structure 2.2.1 Metamorphic (index) mineral 3.2.1 Fault 2.2.2 Ore mineral 3.2.2 Fault zone 3.2.3 Shear zone

1.3 Thrust-bounded unit 3.3 Fracture (‘tectonostratigrahic unit’)

1.4 Lithotectonic unit 3.4 Fabric 1.4.1 Crustal Province 3.4.1 Foliation 1.4.2 Tectonic Province 3.4.2 Gneissic banding/ 1.4.3 Structural Province migmatite veining 1.4.4 Geologic Region 3.4.3 Lineation

3.5 Layering

3.6 Sedimentary structure

23 Geological Survey of Finland, Bulletin 412 Niina Ahtonen, Jarmo Kohonen, Jouni Luukas, Antti E. K. Ojala, Jukka-Pekka Palmu and Jouni Vuollo

3 SPATIAL OBJECTS TYPES (polygons, lines, points) AND MAIN FEATURE CLASSES

The main objective here is to connect the geologi- those data do not have a direct connection to the cal features (or feature classes) used in portrayal of division of the thematic layers (Map Themes). These regional geology to spatial object types. Basically map features (e.g. observation locations, structural the object type (polygon / line) is dependent on strike/dip symbols) are omitted from Table 2. In the map scale and all features can be linked to any some cases map-unit polygons are too small to spatial object type. Table 2 describes the linking in show at scale and are presented as point symbols map scales currently used at GTK. The point data, (e.g. kimberlites, impact rocks) and these cases are features linked only to points, form a special case. included to Table 2. All point data sets can be displayed in any scale and

Table 2. The linked to Table 1 (numbers) and spatial objects (Polygon / Line) corresponding to those in GTK Regional Geology Maps. Features occurring only as points are omitted (see text). X = in use; (X) possible but not in use with core data

Polygon Line (Point)

1 Geologic Unit

1.1 Litostratigraphic unit X (X)

1.2 Lithodemic unit X (X)

1.3 Thrust-bounded X (‘tectonostratigrahic’) unit

1.4 Lithotectonic unit X

2 Earth Material

2.1.1 Rock (type)* X X (X) symbol

2.1.1.1.1 Regolith/Paleosol (X)

2.1.1.1.2 Hydrothermally (X) altered rock

3 Geologic Structure

3.1. Fold (axial plane trace) X

3.2.1 Fault X

3.2.2 Fault zone** (X) (1M-10M scale)

3.2.3 Shear zone** (X) (1M-10M scale)

3.3 Fracture X

3.4.1 Foliation (trend) X

0.0 Undefined structural trend / X formline

3.4.2 Migmatite veining / Gneissic banding (trend)

3.5.1 Layering (trend) X (‘bedding’)

*rock type not only material property; partly depends on texture; e.g. gneisses, pyroclastic rocks **zones will be presented spatially as collection of other features (e.g. faults, fractures)

24 Geological Survey of Finland, Bulletin 412 GTK Map Data Architecture: the core of the developing National Geological Framework of Finland

4 DIVISION OF BEDROCK MAP THEMES

Thematic division of the map data is building on the – Static (no regular update) work done over the years with GTK. Main reasons • Topical Themes for the current restructuring are: (1) to improve the – Metamorphic Domains documentation; (2) to provide clear concepts and – Other themes currently mostly data sets cor- definitions in all levels; (3) to refine the terminology responding to products between the (digital) map data and the (digital) map – IPR: reference to compiler(s) required; Access: products and (4) to clarify update responsibilities All in GTK; License: mostly Open License (see and procedures. the corresponding products) or defined in data • Core Themes set metadata – Regional Master Data (spatial); map features – Update: Static (no regular update; possible arranged and attributed according to the best update by compilers) available classification systems / standards • Applied Themes (currently no themes defined) – Core part of GTK Corporate Data (internal GTK system; access: all in GTK) The more detailed description and documenta- – Regular update by GTK (standard procedure tion, like attribute and value lists, database struc- and responsibilities defined) tures and feature class relationships diagrams are • Generalized Themes developed and maintained as part of the GTK MDA – Data sets corresponding to products (general- documentation. Also MDA documentation structure, ized/modified from Regional Master Data) Finstrati / Finstruct descriptions and the glossary of – Theme: DigiKP200 key terms will be presented in separate documents. – IPR: GTK corporate; Access: All in GTK; DigiKP themes (Core Themes ‘Lithological Unit’ License: see product ‘Kallioperä 1:200 000 and ‘Structure’) are the main source data for the / Bedrock of Finland 1:200 000’ generalized theme DigiKP200, which is the most – Regular update by GTK frequently used compilation in various online prod- – All other themes: uct and services. The other Core Themes are indi- – IPR: reference to compilers recommended; cated by CT in the theme name. In the following: Access: All in GTK; Open License (see the P=polygon, L=line, Pt=point. corresponding products)

A) Core Themes; Bedrock

1 DigiKP_Lithological_Unit (Linked to FinstratiKP) – Interbed (e.g. black shale, carbonate rock, Main feature classes (FIN: pääkohdeluokat): conglomerate) • Lithostratigraphic/Lithodemic unit P • (Minerals Pt)* • Dyke L (Lithodemes; P/L depends on resolu- • Hydrothermally altered rock (alteration zone) tion) NOTE: NOTE: • ’Rock type’ is here the main descriptor of the map • For description of the units – see FinstratiKP feature defining the P/L • ’Main rock type’ is here an attribute of the map • Rock type L features are spatial lithological fea- the geological unit tures (located) – not structural pattern lines (see • Dyke / dyke swarm is defined in FinstratiKP as CT_KP Structure) lithodeme (suite) • Dykes are mainly defined as lithodeme (see • For ’Dyke swarms’ – see ’topical themes’ DigiKP Lithological Unit); the dyke rock here is a rock type; not a lithodemic unit 2 CT_KP_Rock Type • *Metamorphic index minerals and ore minerals Main feature classes (FIN: pääkohdeluokat): may be presented as point symbols • Rock type P • Rock type L 3 CT_KP_Thrust-bounded Unit – Vein (e.g. large Q-veins) (Linked to FinstratiKP) – Dyke rock (e.g. diabase, lamprophyre) Main feature classes (FIN: pääkohdeluokat):

25 Geological Survey of Finland, Bulletin 412 Niina Ahtonen, Jarmo Kohonen, Jouni Luukas, Antti E. K. Ojala, Jukka-Pekka Palmu and Jouni Vuollo

• Tectonostratgraphic unit* P – Migmatite veining trend • Allochthon P – Neosome • Thrust block P – Paleosome • Thrust stack P – Other formlines • Thrust sheet P – Magnetic trace trendline NOTE: – EM trace trendline • See Luukas & Kohonen (2021; this volume) for – Undefined structural trend (muotoviiva) details of the classification esim. vanhat muotoviivat, joiden tuotanto- • *Tectonostratigrahic unit is here a subclass of tapaa ei tunneta thrust-bounded unit NOTE: • Characterization of the features mainly in attrib- 4 CT_KP_Lithotectonic Unit (Linked to FinstratiKP) ute table (description partly in Finstruct) Main feature classes (FIN: pääkohdeluokat): • *No spatial feature in this theme; all defined and • Crustal Province P named in Finstruct • Tectonic Province P • Any spatial features (faults, fractures) may be • Structural Province P linked to a zone (defined in Finstruct) • Geologic Region P – Fault, fracture (fold) are the basic units (like • Suture zone boundary* L Fm) NOTE: – Basic units may be arranged under fault zone, • See Kohonen et al. (2019) for details of the shear zone (like Group) classification • Fault zone corresponds to ‘brittle/semiductile • *Suture zone (or Cryptic suture zone) is the area shear zone’ between the Tectonic Provinces; spatially defined – system of faults by Tectonic Province boundaries – set of faults related to the same major structure (e.g. Suhmura thrust zone) 5 DigiKP_Structure (The named structures linked • Shear zone refers to a zone with ductile / semi- to Finstruct) ductile zone of strain partitioning Main feature classes (FIN: pääkohdeluokat): – system of faults and/or smaller high strain • Fault L elements • Fracture L – set of faults within a regional high strain zone • (Fault zone)* (e.g. Kynsikangas shear zone) • (Shear zone)* • The difference between Fault zone and Shear • Fold axial plane trace L zone is indistinct • Form line L – Layering trend (primary) 6 CT_KP_Subaereal_weathering / Phanerozoic – Foliation trend sedimentary cover remnants / Bedrock relief – Gneissic banding trend (Proposed; waiting for specification)

B) Generalized themes (data sets); Bedrock

1 DigiKP200 (corresponding map product: Kallioperä • Dykes1M L 1:200 000 / Bedrock of Finland 1:200 000) • Kimberlites1M Pt Feature classes (FIN pääkohdeluokat): • Meteorite_impacts1M pt • Litostrat/Lithodem 200 P • Structural line 1M L • Structural lines 200 L • Tectonic Province P NOTE: Feature classes refer to generalized (200) version of the corresponding core theme 3 KP1M_yleistetty (corresponding map product: Yleistetty kallioperä 1:1 000 000 / Generaliserad 2 DigiKP1M (corresponding map product: Kallioperä berggrund 1:1 000 000 / Generalized Bedrock of 1:1 000 000 / Bedrock of Finland 1:1 000 000; see Finland 1:1 000 000) Nironen et al. 2016) • Feature classes (FIN: pääkohdeluokat): Feature classes (FIN: pääkohdeluokat): • Units1My P • Units1M P • Dykes1My L

26 Geological Survey of Finland, Bulletin 412 GTK Map Data Architecture: the core of the developing National Geological Framework of Finland

• Kimberlites1M Point 6 KP_2M_2001 (corresponding printed map product: • Meteorite_impacts1M point Koistinen et al. 2001) • Structural line 1My L • Units2M P • Dykes2M L 4 DigiKP5M (corresponding map product: Kallioperä • Structural line 2M L 1:5 000 000/1:10 000 000 / Bedrock of Finland • etc. 1:5 000 000/1:10 000 000; Mikkola 2017) • Units5M P 7 KP_1M_1997 (corresponding printed map product: • Structural line 5M L Korsman et al. 1997) • Units1M P *** 5 DigiKP10M (corresponding map product: Mikkola • Dykes1M L *** 2017) • Kimberlites1M Point *** • Units10M P • etc. • Structural line 10M L

C) 2D Topical themes (Bedrock) 1 Metamorphic Domains (see Hölttä & Heilimo 2017; Metamorphic map of Finland) 2.2. Structural sequence interpretation (xxxxxx, • Isograd pre-peak 1M 20XX; just an example – there can be several ver- • Isograd peak 1M sions by different compilers) • Isograd overprint 1M X. Metallogenic Provinces (Proposed; preliminary • Isograd overprint2 1M planning in progress) X. Mineral Systems (Topical theme or Core theme??) 2 Regional structural sequence (interpretation) (Proposed; waiting for specification) X. Dyke swarms (Proposed; waiting for revision / 2.1 Structural sequences in Central and Northern checking) Finland (Luukas 202X; specification and compila- X. Black Shales (Proposed; waiting for revision / tion in progress) checking) • Fold hinge trace (Dn to Dn+x) • etc. D) Applied themes; Bedrock 1 Aggregates (Proposed; waiting for specification) 2 Engineering geology (Proposed; waiting for specification)

REFERENCES

Ahtonen, N., Kohonen, J., Luukas, J., Ojala, A. E. K., Pal- (eds) 1997. Suomen kallioperäkartta – Berggrunds mu, J.-P. & Vuollo, J. 2021. GTK Map Data Architec- karta över Finland – Bedrock map of Finland 1:1 000 000. ture: the core of the developing National Geological Geological Survey of Finland. Framework of Finland. In: Kohonen, J. & Tarvainen, Luukas, J. & Kohonen, J. 2021. Major thrusts and thrust- T. (eds) Developments in map data management and bounded geological units in Finland: a tectonostra- geological unit nomenclature in Finland. Geological tigraphic approach. In: Kohonen, J. & Tarvainen, T. Survey of Finland, Bulletin 412. (this volume). Avail- (eds) Developments in map data management and able at: https://doi.org/10.30440/bt412.1 geological unit nomenclature in Finland. Geological Hölttä, P. & Heilimo, E. 2017. Metamorphic map of Fin- Survey of Finland, Bulletin 412. (this volume). Avai- land. In: Nironen, M. (ed.) Bedrock of Finland at the lable at: https://doi.org/10.30440/bt412.3 scale 1:1 000 000 – Major stratigraphic units, meta- Mikkola, P. 2017. Yleistetty Suomen kallioperäkartta, sii- morphism and tectonic evolution. Geological Survey hen liittyvät oheismateriaalit sekä siitä tehdyt yleis- of Finland, Special Paper 60, 77–128. Available at: tykset. Geological Survey of Finland, archive report http://tupa.gtk.fi/julkaisu/specialpaper/sp_060_ 50/2017. 8 p., 2 app. Available at: http://tupa.gtk.fi/ pages_077_128.pdf raportti/arkisto/50_2017.pdf Koistinen, T., Stephens, M. B., Bogatchev, V., Nordgulen, Nironen, M., Kousa, J., Luukas, J. & Lahtinen, R. (eds) Ö., Wennerström, M. & Korhonen, J. 2001. Geologi- 2016. Geological Map of Finland: Bedrock 1:1 000 000. cal map of the Fennoscandian Shield, scale 1:2 000 00. Geological Survey of Finland. Available at: http://tupa. Geological Survey of Finland. gtk.fi/kartta/erikoiskartta/ek_097_300dpi.pdf Korsman, K., Koistinen, T., Kohonen, J., Wennerström, M., Ekdahl, E., Honkamo, M., Idman, H. & Pekkala, Y.

27 Geological Survey of Finland, Bulletin 412 Niina Ahtonen, Jarmo Kohonen, Jouni Luukas, Antti E. K. Ojala, Jukka-Pekka Palmu and Jouni Vuollo

APPENDIX 2 2.2. 2021

STRUCTURED SPATIAL MAP DATA; SUPERFICIAL DEPOSITS; MAP THEMES AND MAIN FEATURE CLASSES

J.-P. Palmu, A. E. K. Ojala & J. Kohonen

1 GENERAL DESCRIPTION OF SPATIAL MASTER DATA (‘GTK Superficial deposits map database’)

The GTK superficial deposits map database is part according to defined classification systems. The of the GTK Map Data Architecture (see Ahtonen et Core Themes (spatial master data) and the linked al. 2021; this volume). This document describes the non-spatial database (FinstratiMP) constitute the current structure of the spatial superficial deposits Regional Master Data (Superficial deposits), which map data (interpreted data): (1) the underpinning are maintained and updated on a regular basis by conceptual model, (2) the map features arranged GTK. Regional Master Data form the source for according to the Geological Concept hierarchy and both generalized datasets and thematic datasets (3) the division into map themes. (Fig. 1). A key part of the system is the Core Themes. Core themes contain the map data structured

Glacial dynamics Interpretation 1M • GD compilation

Scientific • Deglaciation • Ancient shorelines SUPERFICIAL DEPOSITS Regional Master Data Groundwater -Core themes (spatial) -Linked databases (non-spatial) • Aquifer structures • Other groundwater studies

Engineering Interpretation New Core Themes Geology Generalization DigiMP Generalization * DigiMP_1M map Geological data 200 • Bedrock surface Map Units * No regular update by GTK • Overburden thickness • MLG units • Fine sediment thickness • Lithological units Geological units • Glacial dynamic Finstrati provinces and regions Geological Units - Acid Sulphate • Morpho-litho-genetic Description Soil • Lithostratigraphic • • Risk area evaluation Allostratigraphic • Risk area mapping Lithological units

Applied Aggregates

• Resource investigations • Sediment type technical properties

Fig. 1. The vision and functionality of the GTK Map Data Architecture for superficial deposits. The Regional Master Data (spatial and non-spatial) forms the core, which is regularly updated by GTK. The generalized theme set of DigiMP 200 is updated regularly, while DigiMP 1M is not. (The scientific and applied themes on the left are either ongoing (light green) or planned components (red) of the system.)

28 Geological Survey of Finland, Bulletin 412 GTK Map Data Architecture: the core of the developing National Geological Framework of Finland

2 CONCEPTUAL FRAMEWORK FOR REGIONAL GEOLOGICAL DATA (superficial deposits)

The main feature classes are arranged according to further arrangement of map features into thematic the NADM-C1 top-level Geologic Concept hierarchy layers known as ‘Map Themes’. (Fig. 1 and Table 1). The basic idea is to support the

Geologic Concept

1. Geologic Unit 2. Earth Material

Compound Organic Lithostratigraphic Allostratigraphic Biostratigraphic Mineral Material Material Unit Unit Unit

Unconsolidated Rock 3. Geologic Structure Material

Sedimentary Fold Fault Fabric Layering structure

Fig. 2. Diagram displaying the NADM-C1 top-level Geologic Concept hierarchy.

Table 1. The main feature classes used in GTK superficial mapping arranged according to the NADM-C1 top-level Geologic Concepts. Terms directly corresponding to NADM-C1 are indicated in grey.

1 Geological Unit 2 Earth Material 3 Geological Structure

1.1 Lithostratigraphic unit 2.1 Compound material 3.1 Fold 2.1.1 Unconsolidated material 3.1.1 Glacial deformation fold 2.1.1.1 Gravel 2.1.1.2 Diamicton 2.1.1.3 Sand 2.1.1.4 Mud 2.1.2 Rock Material 2.1.2.1 Weathered rock (Regolith/Paleosol)

1.2 Allostratigraphic unit 2.3 Organic material 3.2 Sedimentary external structure 2.3.1 Peat 3.2.1 Depositional structure 2.3.2 Organic-rich sediment 3.2.2 Erosional structure 3.2.3 Dep./eros. structure 3.2.4 Synsedimentary def. structure 3.2.4.1 (Drumlin) lineation

1.3 Morpho-lithogenetic unit 2.4 Dumped material 3.3 Fault 3.3.1 Postglacial fault

1.4 Glacial dynamic unit

29 Geological Survey of Finland, Bulletin 412 Niina Ahtonen, Jarmo Kohonen, Jouni Luukas, Antti E. K. Ojala, Jukka-Pekka Palmu and Jouni Vuollo

3 SPATIAL OBJECT TYPES (POLYGONS, LINES, POINTS) AND MAIN FEATURE CLASSES

The main objective here is to connect the geological features linked only to points, form a special case. features (or feature classes) used in the portrayal of All point data sets can be displayed at any scale, regional geology to spatial object types. Basically, and these data do not have a direct connection to the object type (polygon / line) is dependent on the division of the thematic layers (Map Themes). the map scale and all features can be linked to any These map features (e.g. observation locations) are spatial object type. Table 2 describes the linking at omitted from Table 2. map scales currently used by GTK. The point data,

Table 2. The link to Table 1 (numbers) and spatial objects (Polygon / Line) corresponding to those in GTK Regional Geology Maps. Features only occurring as points are omitted (see text). X = in use; (X) possible but not in use with core data

Polygon Line (Point) 1 Geological Unit 1.1 Lithostratigraphic unit (X) (X) 1.2 Allostratigraphic unit (X) (X) 1.3 Morpho-lithogenetic unit X X 1.4 Glacial dynamic unit X 1.5 Biostratigraphic unit (X) 2 Earth Material 2.1.1.1 Gravel X 2.1.1.1 Diamicton X 2.1.1.1 Sand X 2.1.1.1 Mud X 2.1.2.1 Regolith/Paleosol (X) 2.3.1 Peat X 2.3.2 Organic-rich sediment X 0.0. Bedrock outcrop / thin overburden 3 Geological Structure 3.3.1 Postglacial fault (X) 3.2.4.1 (Drumlin) lineation X

4 DIVISION OF SUPERFICIAL DEPOSIT MAP THEMES

The thematic division of the map data builds on the • Core Themes work done over the years at GTK. The main reasons – Regional Master Data (spatial); map features for the current restructuring are to: (1) improve the arranged and attributed according to the best documentation; (2) provide clear concepts and defi- available classification systems/standards nitions at all levels; (3) harmonise the terminology – Core part of GTK Corporate Data (internal GTK between the (digital) map data and the (digital) system; access: all at GTK) map products and (4) clarify the responsibilities – Regular update by GTK (standard procedure and procedures for updating. and responsibilities defined)

30 Geological Survey of Finland, Bulletin 412 GTK Map Data Architecture: the core of the developing National Geological Framework of Finland

• Generalized Themes such as attribute and value lists, database struc- – Data sets corresponding to products (general- tures and feature class relationship diagrams, are ized/modified from Regional Master Data) developed and maintained as part of the GTK MDA – Theme: DigiMP200 (not finalized) documentation. The MDA documentation structure, – IPR / Access / License Finstrati descriptions and glossary of key terms will – Regular update by GTK also be presented in separate documents. – All other themes: DigiMP themes (Core Themes ‘MLG Unit’ and – IPR: reference to compilers recommended; ‘Sediment Type’) are the main source data for the access: all at GTK; Open License (see the generalized theme DigiMP200, which will be the corresponding products) most frequently used compilation in various online – Static (no regular update) products and services. The Core Themes are indi- • Topical Themes (currently no themes defined) cated by ‘CT’ in the theme name. In the following: • Applied Themes (currently no themes defined) P = polygon, L = line, Pt = point. The more detailed descriptions and documentation,

A) Core Themes (Superficial deposits)

1 CT_MP_MLG_Unit (Linked to FinstratiMP) (Will 2 CT_MP_Sediment Type be finalized in 2020) (Lithological map units) Main feature classes (FIN: pääkohdeluokat): Main feature classes (FIN: pääkohdeluokat): • Glacial dynamic unit P • Sediment type P • Morpho-lithogenetic unit P – Gravel • Genetic deposit type P – Diamicton • *Drumlin lineation L – Sand NOTE: – Mud • For feature classes, see Palmu et al. (2021; this – Peat volume) – Organic-rich sediment • Structure included in the unit theme due to the NOTE: lack of a theme devoted to structures • Compiled from 1:20k, 1:50k, 1:100k and 1:200k map sheet data; resolution variable • An upgrade proposed

B) Generalized themes (datasets (Superficial deposits)

1 DigiMP200 (Proposed; waiting for specification) 2 DigiMP1M (Proposed; waiting for Feature classes (FIN: pääkohdeluokat): specification) • MLG 200 P • Sediment Type 200 P 3 MP_1M_1993 (Corresponding printed map product: NOTE: Feature classes refer to the generalized (200) Niemelä et al. 1993) version of the corresponding core theme

C) Topical themes (Superficial deposits)

1 Ancient shorelines 2 Acid sulphate soils

D) Applied themes (Superficial deposits)

1 Aggregates (gravel, sand) (Proposed; waiting for 3 Groundwater specification) • Interpolated bedrock surface • Areas suitable for aggregate production • Interpolated groundwater table

2 Engineering geology (Proposed; waiting for specification)

31 Geological Survey of Finland, Bulletin 412 Niina Ahtonen, Jarmo Kohonen, Jouni Luukas, Antti E. K. Ojala, Jukka-Pekka Palmu and Jouni Vuollo

REFERENCES

Ahtonen, N., Kohonen, J., Luukas, J., Ojala, A. E. K., Pal- Palmu, J.-P., Ojala, A. E. K., Virtasalo, J., Putkinen, N., mu, J.-P. & Vuollo, J. 2021. GTK Map Data Architec- Kohonen, J. & Sarala, P. 2021. Classification system ture: the core of the developing National Geological of Superficial (Quaternary) Geologic Units in Finland. Framework of Finland. In: Kohonen, J. & Tarvainen, In: Kohonen, J. & Tarvainen, T. (eds) Developments T. (eds) Developments in map data management and in map data management and geological unit no- geological unit nomenclature in Finland. Geological menclature in Finland. Geological Survey of Finland, Survey of Finland, Bulletin 412. (this volume). Avail- Bulletin 412. (this volume). Available at: https://doi. able at: https://doi.org/10.30440/bt412.1 org/10.30440/bt412.4 Niemelä, J., Ekman, I. & Lukashov, A. (eds) 1993. Suomen ja Venäjän Federaation luoteisosan maaperä ja sen raaka-ainevarat 1:1 000 000. Lehti 1 Länsiosa. Qua- ternary deposits of Finland and northwestern part of Russian Federation and their resources 1:1 000 000. Sheet 1 Western part. Geological Survey of Finland. Available at: https://tupa.gtk.fi/kartta/erikoiskartta/ ek_027.jpg

32 Developments in map data management and geological unit nomenclature in Finland Edited by Jarmo Kohonen and Timo Tarvainen Geological Survey of Finland, Bulletin 412, 33–80, 2021

CLASSIFICATION OF REGIONAL-SCALE TECTONIC MAP UNITS IN FINLAND

Jarmo Kohonen1*), Raimo Lahtinen1), Jouni Luukas2) and Mikko Nironen1)

Kohonen, J., Lahtinen, R., Luukas, J. & Nironen, M. 2021. Classification of regional-scale tectonic map units in Finland. Geological Survey of Finland, Bulletin 412, 33–80, 9 figures and 7 tables.

We introduce a novel classification system for the different types of geological provinces. The proposed categories are validated by a provisional division of regional-scale tectonic map units in Finland. Our contribution clarifies the connection between the prevailing tectonic evolution model and the national map compilations by providing a coherent classification system and the corresponding identification of tectonic map units in Finland.

In the last twenty years, modelling of the tectonic evolution of the Finnish bedrock has made major advances, and structural interpretation has become an increasingly important tool in the reconstruction of the overall geological representation. At the same time, geological map data models are of growing importance as a standard basis for developing interoperable geological map databases. The systematic management of geological map data raises a need for structured terminology for regional-scale tectonic map units.

Our approach emphasizes geoscientific concepts, geological relationships and their representation on geological maps. On the conceptual level, geological provinces constitute abstract scientific elements such as orogens, arc complexes, drifting continental blocks and collision zones. This conceptual framework underlying geological map data must be presented, because it forms the basement of the classification and may also be vulnerable to changes with increased geological understanding. We provide key term definitions, key attributes for the map feature characterization and apply the generic conceptual model (NADM-C1) and international vocabularies (CGI GeoSciML) whenever possible.

A regional-scale tectonic map unit is defined as a spatial representation of a crustal segment relevant in understanding the tectonic set-up of the Finnish bedrock. The units are divided into three major categories. A crustal province (CP) represents a segment of continental crust that records a similar range of radiometric (igneous) crystallization ages. A tectonic province (TP) is conceptually defined as a tectonic block transported with respect to adjacent blocks by tectonic processes and having a tectonic history significantly different from each other. A structural province and the lower ranks of the category (LT-FIN-SP) classifies map units with structural characteristics significantly different from the adjoining areas. The tectonic features of the province definitions are genetically related, but the three categories (LT-FIN-CP /-TP /-SP) are all conceptually defined independently, which allows both the subdivision and spatial overlap of the map units.

Province boundaries are fundamental spatial features separating adjacent tectonic map units. We provide both description and spatial definition of the suture zones. The structural province boundaries display, for the first time, the extent of the Svecofennian structural overprint within the Karelia Tectonic Province in eastern and northern Finland. The relationships between the novel classification system, tectonic terminology and time-stratigraphy in Finland are briefly discussed, and some redefinition of the terminology is suggested. Finally, the article is closed is by a review and minor revision of the geological region names in Finland.

33 Geological Survey of Finland, Bulletin 412 Jarmo Kohonen, Raimo Lahtinen, Jouni Luukas and Mikko Nironen

Keywords: Geological province, lithotectonic classification, map unit, tectonic model, Finland

1) Geological Survey of Finland, P.O. Box 96, FI-02151 Espoo, Finland 2) Geological Survey of Finland, P.O. Box 1237, FI-70211 Kuopio, Finland

* Corresponding author, e-mail: [email protected]

https://doi.org/10.30440/bt412.2 Editorial handling by Timo Tarvainen. Received 16.9.2020; Received in revised form 14.12.2020; Accepted 2.2.2021

34 Geological Survey of Finland, Bulletin 412 Classification of regional-scale tectonic map units in Finland

CONTENTS

1 INTRODUCTION...... 37

2 NEW CLASSICATION SYSTEM FOR REGIONAL-SCALE TECTONIC MAP UNITS...... 38 2.1 Geological province as a concept...... 38 2.2 Classification and categories of the geological provinces...... 39 2.2.1 Crustal province (LT-FIN-CP)...... 41 2.2.2 Tectonic province (LT-FIN-TP)...... 41 2.2.2.1 Suture zone, the tectonic province boundary...... 43 2.2.3 Structural Province and the classification system (LT-FIN-SP) for structural map units ...... 43 2.2.4 Description of province boundaries...... 44

3 LITHOTECTONIC DIVISION OF REGIONAL-SCALE TECTONIC MAP UNITS IN FINLAND...... 45 3.1 Provinces and tectonic boundaries in Finland: an overview...... 45 3.2 Crustal provinces...... 46 3.2.1 Division of crustal provinces...... 46 3.3 Tectonic provinces (Paleoproterozoic)...... 48 3.3.1 Division of tectonic provinces ...... 48 3.3.2 Suture zones...... 50 3.4 Structural provinces...... 50 3.4.1 Division and boundaries of structural provinces ...... 50 3.4.2 Paleoproterozoic structural provinces...... 51 3.4.3 Paleozoic Kilpisjärvi Structural Province...... 51 3.5 Discussion and recommendations...... 54 3.5.1 Applicability of the (LT-FIN) province division in Finland...... 54 3.5.2 Potential new categories and extension of the LT-FIN system...... 55 3.5.3 Terminological comments and recommendations...... 55 3.5.3.1 Time–stratigraphic terms and terminology of orogenies...... 55 3.5.3.2 Crustal, tectonic and structural provinces in relation to orogens...... 57 3.5.3.3 Present-day map units in relation to paleoterms ...... 57 3.5.3.4 Summary of recommendations...... 57

4 REGIONAL-SCALE TECTONIC MAP UNITS IN FINLAND: DESCRIPTION...... 58 4.1 Crustal provinces in Finland...... 58 4.1.1 Archean Province...... 58 4.1.1.1 Central Karelia Subprovince...... 58 4.1.1.2 Central Lapland Subprovince...... 59 4.1.1.3 Northern Lapland Subprovince...... 59 4.1.2 Svecofennian Province...... 60 4.1.2.1 Northern Svecofennia Subprovince...... 60 4.1.2.2 Southern Svecofennia Subprovince...... 61 4.2 Tectonic provinces in Finland...... 61 4.2.1 Karelia Province...... 61 4.2.1.1 Iisalmi–Pudasjärvi Subprovince...... 62

35 Geological Survey of Finland, Bulletin 412 Jarmo Kohonen, Raimo Lahtinen, Jouni Luukas and Mikko Nironen

4.2.2 Norrbotten Province...... 63 4.2.3 Kola Province...... 63 4.2.4 Central Finland Province...... 64 4.2.5 Southwestern Finland Province...... 64 4.3 Structural provinces in Finland...... 65 4.3.1 Svecokarelia Structural Province...... 65 4.3.1.1 North Karelia–Kainuu Subprovince...... 66 4.3.1.2 Kuopio–Iisalmi–Oulujärvi Subprovince...... 66 4.3.1.3 North Ostrobothnia Subprovince...... 67 4.3.2 Norbotten–Lapland Structural Province...... 68 4.3.3 Muonio–Ropi Structural Province...... 69 4.3.4 Hetta–Jergul Structural Province...... 69 4.3.5 Kola–Lapland Structural Province...... 70 4.3.5.1 Kaldoaivi Subprovince...... 70 4.3.5.2 Inari Subprovince...... 71 4.3.5.3 Sodankylä Subprovince...... 71 4.3.6 Kilpisjärvi Structural Province (Paleozoic) ...... 72

5 GEOLOGICAL REGIONS IN FINLAND...... 73

ACKNOWLEDGEMENTS...... 73

REFERENCES ...... 74

36 Geological Survey of Finland, Bulletin 412 Classification of regional-scale tectonic map units in Finland

1 INTRODUCTION

The construction of digital geological map databases – Extension of the GTK bedrock map unit system challenges national geoscience agencies to develop (FinstratiKP) with tectonic map units suited to a digital information infrastructure that supports crustal-scale 3D modelling the arrangement of geological features into spatial • Systematic, compliant with international stand- and non-spatial database structures. The challenge ards with appropriate respect for the national is not just technical but requires nationally coor- tradition and mapping legacy dinated definition of conceptual models describing • Flexible to allow changes and extensions with geology and scientific language that allows stand- increasing scientific understanding ardized descriptions and classification. Key concept definitions, classification systems and data mod- Many key aspects of geology (e.g., the formation of els form a basis for solid database structures and crust, tectonic evolution, igneous activity) are tied improve scientific communication. together in a complex and fascinating manner. As The Geological Survey of Finland (GTK) has a consequence, the definitions for geological con- the responsibility for developing regional geo- cepts and terms overlap and may be poorly defined. logical terminology in Finland. GTK has no formal The overall richness of and some inconsistency in authority for national standards, but we hope that tectonic terminology is easy to notice by inspect- the lexicons and vocabularies ‘preferred by GTK’ ing geological glossaries or by comparing national would gradually develop towards de facto national map legends. The situation reflects both the long standards. The principles and definitions presented backlog of geology as a science and methodologies here are part of a more comprehensive scheme (GTK developed in different countries and in different Map Data Architecture; see Ahtonen et al. 2021; this geological environments. volume) for use in computer-based geoscientific The current approach emphasizes geoscientific information systems in Finland. Geological survey concepts, geological relationships and their rep- organizations are in position to support the devel- resentation on geological maps. The impetus for opment towards globally standardized terminolo- our work was a desire to clarify the connection gies and interoperable information infrastructures. between the prevailing models of tectonic evolu- Sufficient documentation of the national approach tion and national map compilations. Our principal is one way ahead on a practical level. aim was the identification and coherent division of Our fundamental impetus is to provide new tools regional-scale tectonic map units, not a compre- for both the practical management of tectonic map hensive review of various tectonic evolution models. units and more theoretical geological modelling. Our contribution consists of four parts. First, we The overall objective is to supplement the national present (Chapter 2) a novel classification system geological map data model by defining the key for the different types of geological provinces. In concepts and classification tools for the systematic Chapter 3, the proposed categories of the classifica- management of regional-scale tectonic map units in tion system are validated by a provisional division Finland. The request for the province classification of lithotectonic map units in Finland. Chapter 4 system was specified as follows: contains descriptions of the presented lithotectonic • Applicable to practical purposes such as: units (provinces) and their boundaries. Chapter 5 – Map compilations at various scales, index is a minor revision of the geological region names maps of scientific papers in Finland. – National legends and feature catalogues of regional maps, profiles and 3D models

37 Geological Survey of Finland, Bulletin 412 Jarmo Kohonen, Raimo Lahtinen, Jouni Luukas and Mikko Nironen

2 NEW CLASSICATION SYSTEM FOR REGIONAL-SCALE TECTONIC MAP UNITS

2.1 Geological province as a concept

With the emergence of a tectonic approach to (e.g., province, tectonic province, orogenic domain, regional and national geological map compilations, crustal domain, terrane). Especially challenging is stratigraphic and lithological units have typically the concept of a ‘tectonic province’; (2) The term been grouped (both spatially and conceptually) into ‘province’ has been in use in many connections, ‘geological provinces’ – in most cases fully reason- which are not always tectonic; (3) Tectonic prov- ably, but without any definition for the province. inces and many other tectonic concepts are related Glossary of Geology (Neuendorf et al. 2005) pro- to both geological time and the spatial dimension, vides broad definitions: and the hierarchical relationships of these ‘time– • Province: Large region with similar features or a his- space terms’ may therefore be complex. tory significantly different from the adjacent areas Tectonic province is currently an ambiguous term • Geologic Province: Extensive region with similar that is not included in the Glossary of Geology geolocic history throughout or similar structural, pet- (Neuendorf et al. 2005). Maxwell (1982) stated that rographic or physiographic features “...the continental crust can be divided into series of tectonic provinces, marking the successive development of International examples of the systematic classifica orogenic belts during the course of geological history.” tion of provinces are not many. Geoscience Australia Geoscience Australia (Raymond 2003) defined tec- has provided a national approach (Raymond 2003) tonic provinces as follows: “Groups of provinces linked with definitions of province types. Nonetheless, the by a common tectonic history are designated as tectonic province terminology is not well established, and provinces. Tectonic provinces may contain a collection the need for a clear and geologically justified clas- of sedimentary, igneous, structural, metamorphic and sification system is apparent: (1) as a framework for metallogenic provinces.” the meaningful handling and correlation of the geo- Geological unit is a generic term (see Fig. 1), which logical rock record developed as separate tectonic has in practice been synonymous with a geological entities, and (2) to display plate tectonic models map unit. Nonetheless, in the application of classifi- with spatially overlapping orogens as corresponding cations, there is no fundamental difference between map unit representations. geological maps, 2D vertical sections and 3D mod- The linking of tectonic evolution models and the els. The term for the spatial geometric object may national map unit classification system involves a change, for example, from tectonic province (2D) to combination of two different approaches. On the tectonic block (3D), but the characteristics of the rock conceptual level, regional-scale tectonic geological body typically remain the same. According to the provinces arise from published orogenic evolution NADM-C1 geological concept hierarchy (Fig. 1) and models consisting of rather abstract elements, such GeoSciML terminology, the classification of litho- as arc complexes, drifting continental blocks and tectonic units is the appropriate option for geological collision zones. In contrast, the spatial system con- units such as tectonic and structural provinces. straints are simple and concrete: provinces are map • Lithotectonic unit (see Neuendorf et al. 2005; units having defined boundaries with the adjacent GeoSciML): Geologic unit defined on basis of struc- units. The overall challenges in the classification of tural or deformation features, mutual relations, ori- provinces are severe: (1) Formal definitions are lack- gin or historical evolution. Contained material may ing or very broad, even for commonly used terms be igneous, sedimentary, or metamorphic.

38 Geological Survey of Finland, Bulletin 412 Classification of regional-scale tectonic map units in Finland

Fig. 1. Generalized version of the NADM-C1 (North American Geologic Map Data Model Steering Committee 2004) ‘Geologic Concept’ hierarchy (lower part). In the upper part, the concept of a ‘Geologic Unit’ is defined.

2.2 Classification and categories of the geological provinces

Provinces and other regional-scale tectonic map provided by international working groups, such units are spatial representations (e.g., polygons) as NADM-SLTT (https://ngmdb.usgs.gov/www- of crustal segments relevant in understanding the nadm/), IUGS-CGI GeoSciML (https://cgi-iugs.org/ tectonic set-up of the Finnish bedrock. The defined project/geosciml/) and INSPIRE (https://inspire. key concepts are crucial background information, ec.europa.eu/). Regional-scale tectonic map units, and the conceptual framework underlying geologi- the provinces, are linked to the NADM-C1 frame- cal map data must be presented. This especially true work by the concepts of geologic unit and litho- with tectonic map units because the tectonic models tectonic unit (Fig.1). Consequently, the proposed are vulnerable to changes with increased under- scheme is formally a national lithotectonic classi- standing over time. fication system (LT-FIN) for spatial map units (2D In general, geological map units are established or 3D), and all the lithotectonic units must have a and classified according to different classification link to spatial objects. systems, such as litostratigraphic, tectonostrati- The tectonic map units support the design of graphic and lithotectonic. Conceptual models and national legends and nationwide geological com- data models (e.g. NADM-C1, Boisvert et al. 2016) pilations, but the hierarchy and subdivision also provide support in arrangement of different con- allow application to more detailed scales. One cepts and derived geological units. The presented starting point and benchmark was the pioneer scheme aims to follow, whenever possible, the work ‘Australian Geological Provinces, Regions and recommendations, guidelines and vocabularies Events - A standardised, national approach’, and

39 Geological Survey of Finland, Bulletin 412 Jarmo Kohonen, Raimo Lahtinen, Jouni Luukas and Mikko Nironen the main line of the Australian examples (Bain & • The division of a tectonic province shall be assigned Draper 1997, Raymond 2003) is largely followed, to a specified tectonic model with some novel features and modifications: • Geological provinces and their lower ranks are The major categories (CP - crustal province, TP - linked to the NADM-C1 top-level hierarchy as tectonic province, SP - structural province; Table 1) of lithotectonic units. the lithotectonic classification in Finland (LT-FIN) • All the lithotectonic categories (e.g., different are defined by features that are genetically closely province types) are characterized by a defined related. Nonetheless, the three major province cat- set of key attributes, features such as: egories (Table 1) are all conceptually defined inde- – Genesis, geological age, composition, fabric pendently, which allows both the subdivision and (e.g., structural trend), metamorphic grade, spatial overlap of the map units. The key attributes geological relation (spatial/structural). for each LT-FIN category may be either measurable/ • A new concept of a crustal province is introduced observed or interpreted (see Table 1). and defined.

Table 1. Categories and unit terms in the lithotectonic (LT-FIN) classification.

LITHOTECTONIC DEFINITION IN PRINCIPAL KEY ATTRIBUTES IN UNIT TYPE CATEGORIES UNIT RANKS CHARACTERIZATION*

Crustal Province This paper Province Geological age of continental crust (o) Spatial (LT-FIN-CP) Subprovince Genesis (crustal growth history) (i) Domain Composition (o) Nature of the boundaries (i)

Tectonic Province This paper/Raymond Province Tectonic history (i) Spatial (LT-FIN-TP) 2003; see also Subprovince Nature of the boundaries (i) Nironen 2017a

Structural Province Raymond 2003/ Province Characteristic structural features (o) Spatial; overlapping (LT-FIN-SP) this paper Subprovince Tectonic setting (i) Domain Nature of the boundaries (i/o) Subdomain Other lithotectonic characteristics (o) Possible extensions**:

Sedimentary Province Raymond 2003 Spatial; overlapping

Igneous Province Raymond 2003 Spatial; overlapping

Metamorphic Province Raymond 2003 Spatial; overlapping

Metallogenic Province Raymond 2003 Spatial; overlapping

Regolith-landform Raymond 2003 Spatial Province Informal categories

Geological Region This paper (Part 4); No ranks Geographic location, main lithologies Spatial 2D see also Nironen geological setting et al. 2002

* Attributes are either measurable/observed (o) or interpreted (i) features.

** Examples (originally suggested and defined by Geoscience Australia; Raymond 2003) of possible further categories of the LT-FIN classification.

40 Geological Survey of Finland, Bulletin 412 Classification of regional-scale tectonic map units in Finland

The key terminology and the province hierar- definition ofmajor reworking and isotopic resetting. chy of Raymond (2003) has been adopted. The only Each melting event somewhat resets the isotopic term wider than a province is a superprovince, and system (e.g., anorogenic granites) and each juvenile the lower ranks are subprovince, domain, subdomain increment (e.g., rift-related mafic intrusions) is part and microdomain. The highest rank used here is a of the crustal growth, but these components can province. A new lower-rank LT-FIN unit can be iden- generally be separated from the extensive, orogenic tified and defined on any hierarchical level, but the key crustal volumes. attributes in characterization must remain the same as The unit definition shall contain information presented for the category (see Table 1). For flexibil- related to all the items (i–iv), and the description ity and applicability, incomplete hierarchies (e.g., a of province boundaries shall follow the guidelines domain within a province without a subprovince in presented in Table 2. The definition of a new lower between) are allowed. rank unit must include the name of the parent unit. In all the presented LT-FIN categories, the lower The LT-CP-FIN units shall be defined by the fol- rank unit shall be spatially enclosed by the par- lowing features and attributes: ent (or other higher rank) unit. The map units of (i) Geological age of the continental crust (observed) separately defined categories (crustal, tectonic and • Range of magmatic crystallization ages structural provinces) may spatially overlap each – Continental crustal growth/major reworking other. In addition, different structural provinces and period characteristic for the unit (range of the their subclasses may spatially overlap each other. ages) The categories CP and TP are by the definition – Complete range of geological ages within the meaningful in the presentation of tectonic recon- unit structions. The observation-based SP classification (ii) Genesis (interpreted) offers novel tools to describe regional structural • Description of a major, well-defined stage of units independent of lithological units and to con- orogenic continental crust formation (Province) nect structural provinces to tectonic interpreta- • Description of an orogenic stage of continental tions. On a more practical level, the identification crust formation or a tectonic stage with major of lower-rank SP units (such as structural domains) magmatic reworking of the crust (Subprovince might be a useful procedure to encourage and sys- and other lower ranks) temize structural mapping in Finland. (iii) Composition (observed) (iv) Nature of the province boundaries (interpreted) 2.2.1 Crustal province (LT-FIN-CP) 2.2.2 Tectonic province (LT-FIN-TP) A crustal province is herein defined as a volume of continental crust that records a similar range of radio- We define a tectonic province (TP) as a lithotectonic metric (igneous) crystallization ages. The definition is unit representing a tectonic block (a defined body of tied to the formation of new continental crust, and Earth material) transported with respect to adjacent the crustal provinces typically also display other blocks by plate-tectonic processes and having a tectonic similar features as described by Condie (1997). The history significantly different from the adjoining areas. term ‘crustal province’ has been also used for geo- A tectonic province is a spatially outlined geologi- physically (magnetic and gravity anomaly pattern) cal map unit, but the definition involves both the defined crustal entities (e.g. Bain & Draper 1997), concept of the precursor (active tectonic block) and a method distinctly different from the present the nature of the present boundaries, most typically approach. sutures representing the ancient collision zones. Crustal province is the most deep-seated concept Active tectonic block (ATB) may originate by accretion of the LT-FIN map unit classification, and the key (growth of new continental crust) within volcanic characteristics of the concept are related to a com- arcs or via the break-up of a pre-existing conti- mon crustal growth history and the large-scale nental block. The life span of an ATB comes to an formation of new continental crust (provinces and end when it is laterally accreted by collision and/ subprovinces) or to a major, regional-scale, tectono- or when the particular tectonic transport stage has thermal reworking and magmatic isotopic resetting ended (Fig. 2). Accordingly, the life span of an ATB of a crustal segment (subprovinces and the other is a fundamental part of the characterization of tectonic lower ranks). The main conceptual challenge is the provinces. Tectonic processes may spatially over-

41 Geological Survey of Finland, Bulletin 412 Jarmo Kohonen, Raimo Lahtinen, Jouni Luukas and Mikko Nironen lap each other with geological time, and an ATB on the tectonic evolution model selected. Therefore, is therefore seen as a ‘space–time’ concept (Fig. the defined provinces are potentially vulnerable to 2). However, the resulting (current) tectonic prov- changes and modifications with increasing tectonic ince is an ordinary spatial map unit with defined understanding and the emergence of new models. boundaries. It is essential to note that within the framework of A potential challenge with the tectonic province a tectonic model involving collisions (lateral accre- concept also arises from the ‘space–time’ nature. tion), sutures must exist on a conceptual level, even A laterally accreted block (TP), or part of it, may when their spatial features are poorly defined or depart (as a new ATB) and collide again (as a new inferred. References to the applied tectonic mod- TP). As a result, the successive orogenies may els, the assumed active tectonic block history, and result in spatially overlapping tectonic provinces. boundary descriptions are essential parts of tectonic This complication can be avoided by referring to province characterization. the latest ATB in the definition of a tectonic province. The unit definition shall contain information Tectonic provinces reflect prevailing regional related to all the items (i–ii) and the description of paradigms and their definition is solely dependent the province boundaries shall follow the guidelines

Fig. 2. Schematic diagram addressing the concepts of ‘Active Tectonic Block’, ‘Tectonic Province’ and ‘Crustal Province’.

42 Geological Survey of Finland, Bulletin 412 Classification of regional-scale tectonic map units in Finland given in Table 2. The definition of a new lower rank radiometric age of igneous or metamorphic rocks unit must include the name of the parent unit. The together with other multiple lines of evidence (see TP units will be defined by the following features Moores 1981, Vasey et al. 2019) may provide a first- and attributes: order indication of a cryptic suture. (i) Tectonic history (interpreted) • A cryptic suture zone is a wide suture zone with dif- • Definition of theactive tectonic block correspond- fuse boundaries and collision-related features ing to the tectonic province obscured either by primary gravitational insta- – Origin and tectonic history of the ATB bilities within the thickened crust or reworking – Life span (geological age) of the ATB from by later deformation stages. Variable lithologies initiation to the end of the tectonic transport and age patterns reflecting hybrid continental stage crust mixed from the lower and upper plates are (ii) Nature of boundaries between adjacent tectonic characteristic for cryptic suture zones. provinces (interpreted) Province boundaries are fundamental, not only as The spatial depiction of a suture zone is not a spatial features separating the adjacent map units, straightforward task. Theoretically, the case is sim- but also as the conceptual foundation for the defini- ple: a suture zone separates the domains repre- tion of a tectonic province. Tectonic province bounda- senting upper and lower plates within the collision ries are major tectonic zones, like cryptic suture zone. In practice, suture zones are represented by zones, and their original characteristics may have tectonic slices of uncertain origin, melanges and been substantially obscured by later deformation complex deformation. The collisional structures stages. Thus, a major challenge is the precise loca- are typically modified and overprinted by later tion of province boundaries: the spatial depiction of deformation, multiple re-activation of faults and tectonic provinces is not possible without a definition post-collisional intrusives. The exact boundaries of the boundaries. (and width) of a suture zone can seldom be precisely mapped in the field. Rather, the spatial appearance 2.2.2.1 Suture zone, the tectonic province boundary of the zone can be understood more like a prob- In tectonic terminology, sutures represent the ability function; the lower the spatial accuracy (i.e. remains of ancient collision zones between ter- the wider the outlined suture zone), the better are ranes that are joined together. Due to the lack of the chances that the zone exclusively separates the an internationally accepted tectonic vocabulary, we upper plate domain from the lower plate domain. clarify the key terms and their usage: Post-collisional features (e.g., intrusions, fault • Suture is a concept joining together separate zones) cannot define suture zones, but are still tectonic units that have different plate tectonic, important components of their description. metamorphic and paleogeographic histories. The presence of a suture implies that the tec- 2.2.3 Structural Province and the classification tonic units were once widely separated and either system (LT-FIN-SP) for structural map units oceanic lithosphere or extremely thinned continental lithosphere (proto-oceanic rift basin) once The LT-FIN-SP is a system of mappable structural units existed between the blocks. with descriptions of the unit boundaries and rel- • A suture zone is the area (map unit) where two evant lithogenetic features. The map units represent tectonic plates have joined together through a bedrock segments (defined bodies of Earth material) collision. A suture zone is characterized by the displaying structural characteristics significantly dif- presence of tectonic lenses with varying types of ferent from the adjoining area. The units are charac- lithologies, often including ophiolitic fragments terized by regionally significant structural features or eclogites, and complex networks of mylonitic (such as foliations, lineations, finite strain patterns) shear zones and faults. representing a coherent, geologically meaningful set The preservation potential of oceanic crust is of structures (e.g., structural trend), and the units low, and not all sutures expose ophiolites. The of the same hierarchical level may spatially over- lack of eclogites is also a common feature within lap as a result of superimposed structural features Precambrian suture zones (e.g., van Hunen & Allen differing in age and origin. The generic LT-FIN-SP 2011), and other criteria are needed for their firm characterization is based on regional-scale data (e.g., recognition. Even so, major differences in the structural observations, remote sensing data), and

43 Geological Survey of Finland, Bulletin 412 Jarmo Kohonen, Raimo Lahtinen, Jouni Luukas and Mikko Nironen the origin of the structures is just one key attrib- b. Extension-related setting ute. A structural province is the highest rank of map c. Lateral displacement (transcurrent) related units and it may contain subprovinces, domains and setting subdomains. d. Undefined tectonic setting Within the LT-FIN-SP category the highest • For lower ranks (e.g., subprovince, domain), the rank forms an exception; unlike the lower ranks, a tectonic setting corresponding to the structural structural province is established by linking the observed features defining the unit. structures to a collision zone (or other tectonic, crustal-scale frontier). According to the definition, (iii) Nature of the unit boundaries (interpreted/ collision (or lateral accretion) leads to the genera- observed) tion of a tectonic province. Tectonic transfer in a collision zone results in the regional deformation (iv) Other (relevant) lithotectonic characteristics and transposition of structures on both sides of the (observed) boundary zone. Therefore, tectonic and structural • Additional description in the lower ranks (if provinces are both spatially and causally closely tied required for subprovinces, domains and sub- together. domains) The development of ductile structural features (by recrystallization) has a close linkage to the met- 2.2.4 Description of province boundaries amorphic history of the area, and the metamorphic characterization is part of the SP description. It is The nature of the boundaries is crucial in the char- seen as appropriate, even considering the possibility acterization of all the province categories, and for a for the definition of distinct metamorphic provinces tectonic province, the nature of the boundaries forms (see Table 1) in the future. the conceptual starting point (see Table 1 and Fig. The SP unit definition shall contain information 2). Tectonic boundaries, such as suture zones, may related to all the items (i–iv) and the description be geologically very complex and display various of the province boundaries shall follow the guide- stages of reactivation. Consequently, not all prov- lines given in Table 2. The definition of a new lower ince boundaries necessarily follow lithological rank unit must include the name of the parent unit. boundaries as presented in geological maps. Structural provinces and other SP units are character- The boundaries between the crustal provinces ized by the following features and attributes: and between the tectonic provinces are often not ‘mappable’ in the traditional sense. The essence (i) Characteristic structural features (observed) of the classification lies in conceptual definitions • Structural features defining/characterizing the based on interpretation. In addition, the location unit and the related tectonic event (if applicable) of a boundary may not be spatially well defined; • Structural (foliation, lineation, strain) patterns for example due to the complex nature of a cryp- and trends; description tic suture zone (tectonic province boundary) or due • Metamorphic features linked to the characteristic to the gradational nature of the boundary (e.g., structures (optional) structural province). Nonetheless, the boundaries must be characterized and described by a set of (ii) Tectonic setting of the unit; the origin of the attributes (Table 2). The generic subdivision of dominant structures (interpreted) contacts (Geological structure > Contact; NADM-C1) • For the highest rank (structural province), the fol- in the GeoSciML vocabulary recognizes a province lowing attributes for tectonic setting are used: boundary (Contact > Geological province contact) and a. Collision-related setting provides terminology for further characterization – Foreland fold and thrust belt (peripheral) of the contact type (see CGI GeoSciML geoscience – Retro-arc (foreland) fold and thrust belt vocabularies; http://geosciml.org/resource/). – Intracratonic fold belt (e.g. inboard foreland fold belt) – Magmatic arc fold belt

44 Geological Survey of Finland, Bulletin 412 Classification of regional-scale tectonic map units in Finland

Table 2. Characterization of lithotectonic unit boundaries. The terms corresponding to the GeoSciML/CGI geoscience vocabulary (status 11/2019) are presented in italics.

LITHOTECTONIC TECTONIC CONTACT TYPE SPATIAL CHARACTERISTICS CATEGORY NATURE

Location Nature Width

Crustal province / Collisional Geological province contact >Well defined >Sharp >Line Tectonic province >Cont./Cont. >Cryptic suture zone >Defined >Gradational >Narrow zone >Cont./Arc >Suture zone >Poorly defined >Diffuse >Wide zone >Arc/Arc Lithogenetic contact >Inferred >Undefined >Undefined Non-collisional >Igneous intrusive contact >Transcurrent >Undefined lithogenetic contact Undefined Faulted contact >Fault zone

Structural Geological province contact (Shared) (Shared) (Shared) province n/a (CP/TP) >Well defined >Sharp >Line Faulted contact >Defined >Gradational >Narrow zone >Fault zone >Poorly defined >Diffuse >Wide zone >>Thrust fault zone >Inferred >Undefined >Undefined >>>Frontal ramp >>Transcurrent fault Lithogenetic contact >Igneous intrusive contact >Deformation boundary zone contact

Geological n/a Geographic boundary Region Any geological boundary (Shared) (Shared) (Shared) (see Part 4)

3 LITHOTECTONIC DIVISION OF REGIONAL-SCALE TECTONIC MAP UNITS IN FINLAND

3.1 Provinces and tectonic boundaries in Finland: an overview

In the following, we apply LT-FIN classification logical structures and map unit patterns, the recent system and indroduce the regional-scale tectonic 1:1M map (Nironen et al. 2016) and the explanatory map units in Finland. The description of the units text (Nironen 2017a) are referred to. A vast amount (provinces) is presented in Chapter 4. To aid further of knowledge is condensed in Chapter 4, but due to reading, the geological provinces are arranged in the selected concise format, we merely provide the age groups in Table 3. key references, and the reader is directed to further The research history of the provinces and several references therein. The comprehensive compilation aspects of tectonic modelling are addressed briefly by Lehtinen et al. (2005) is suggested as the first or not at all. For the overall division of the bedrock step for the geological context. and visualization of the main lithologies, major geo-

45 Geological Survey of Finland, Bulletin 412 Jarmo Kohonen, Raimo Lahtinen, Jouni Luukas and Mikko Nironen

Table 3. Geological provinces of Finland.

Crustal provinces Tectonic provinces Structural provinces

Archean Paleoproterozoic Paleoproterozoic

Archean Province Karelia Province Svecokarelia Structural Province > Central Karelia Subprovince > Iisalmi–Pudasjärvi Subprovince >North Karelia–Kainuu Subprovince > Central Lapland Subprovince >Kuopio–Iisalmi–Oulujärvi Subprovince > Northern Lapland Subprovince >North Ostrobothnia Subprovince

Norrbotten–Lapland Structural Province Norrbotten Province Muonio–Ropi Structural Province

Hetta–Jergul Structural Province

(Kola Province) Kola–Lapland Structural Province (Outside Finland) >Kaldoaivi Subprovince Paleoproterozoic >Inari Subprovince >Sodankylä Subprovince Svecofennian Province > Northern Svecofennia Central Finland Province Subprovince Paleozoic > Southern Svecofennia Southwestern Finland Province Subprovince Kilpisjärvi Structural Province

3.2 Crustal provinces

3.2.1 Division of crustal provinces episodes. The two major stages of crustal growth explaining the main division of crustal provinces in The geological evolution of the Finnish bedrock Finland are presented in Figure 3. represents stable cratonic stages and orogenic

Svecofennian Orogeny

Major Archean Karelia Craton New Craton crustal growth Craton (precursor of the East European Craton) break-up Anorogenic bimodal Major magmatism Paleoproterozoic crustal growth Fig. 5

Fig. 3. Simplified diagram with two major stages of crustal growth explaining the division of crustal provinces in Finland. The time span corresponding to Figure 5 is also indicated.

46 Geological Survey of Finland, Bulletin 412 Classification of regional-scale tectonic map units in Finland

Crustal provinces represent the first-order tec- province boundary (e.g., Hietanen 1975, Koistinen tonic map units, which comprise the Fennoscandian 1981, Gaál & Gorbatschev 1987) has been widely Shield and the entire East European Craton. The accepted for decades, and a continent–arc colli- fundamental boundary between the Archean Crustal sion (ca. 1.9 Ga) between the Archean craton and Province and the (Paleoproterozoic) Svecofennian the Paleoproterozoic arc collage is the currently Crustal Province (Table 4 and Fig. 4) has been com- favoured model (e.g., Gaál 1990, Lahtinen et al. prehended since the first reliable age determina- 2005). The boundary between the crustal provinces tions (cf. Kouvo & Tilton 1966, Simonen 1971, 1980, is discussed below as one of the tectonic province Patchett & Kouvo 1986), and the Sm–Nd and Pb–Pb boundaries (Raahe–Ladoga Suture; R–LS; see Table data show an abrupt change from Archean to juve- 6). The complicated assembly of the cryptic suture nile arc lithosphere across the boundary (Vaasjoki zone (R–LS) has recently been reviewed by Lahtinen 1981, Huhma 1986). The collisional nature of the et al. (2015b, 2016).

Table 4. Division of crustal provinces in Finland with a summary of their characteristics (see also Chapter 4).

CRUSTAL Age (Ga) Compositional Crustal growth history Boundaries PROVINCE characteristic characteristics (in Finland; (range) see Table 6)

Archean 2.83–2.70 Tonalite-trondhjemite- A result of Archean orogenic processes; Raahe–Ladoga Province> (3.5–2.6) granodiorite rocks (TTG) details of the orogenic history are poorly Suture (in the SW) with minor coeval known; fully cratonized prior to 2.5 Ga supracrustals

Russia (in the east)

granitoids; supracrustal (ca. 2.4 to 1.98 Ga) within the Archean Chapter 4 Subprovince remnants Province; syn- (ca. 1.88 Ga) to late orogenic granitoids dominant

Granulite Belt (in the SE)

Svecofennian 1.90–1.87 Granitoid complexes with A result of Paleoproterozoic orogenic Raahe–Ladoga Province> (1.93–1.77) coeval supracrustal belts processes; a collage of several volcanic Suture (in the NE) arc complexes; intraforogenic stage at 1.86–1.84 Ga; fully cratonized prior to 1.65 Ga

granite- recycling of PP crust; tectonic cause Chapter 4 Subprovince migmatites are disputable characteristic

*Age of the Paleoproterozoic reworking and recrystallization or igneous activity

47 Geological Survey of Finland, Bulletin 412 Jarmo Kohonen, Raimo Lahtinen, Jouni Luukas and Mikko Nironen

The principle of a ‘major, regional-scale, tectonothermal reworking and isotopic resetting of a crustal segment’ in the definition of the LT-FIN-CP is not straightforward to apply. Even large plutonic complexes like the anorogenic intrusions of the Southern Finland Rapakivi Supersuite, and the area with post-orogenic granites (1.80–1.77 Ga) in Lapland, are not considered as crustal subprovinces, because the sharply cross-cutting intrusions are not seen to represent an overall, regional-scale reworking of the crust. A sufficient classification system for their management as map units is provided by the lithostratigraphic–lithodemic division of the FinstratiKP (Luukas et al. 2017). The possible definition of igneous provinces (see Table 1) might in the future provide new tools for their conceptual modelling and classification.

3.3 Tectonic provinces (Paleoproterozoic)

3.3.1 Division of tectonic provinces

Archean tectonic evolution is poorly known, and no tectonic provinces are hence introduced. Some tentative evolutionary models have been presented (e.g., Slabunov et al. 2006), but at this stage, the understanding seems insufficient to allow the identification of collisional boundaries and the corresponding provinces. Within the Archean Crustal Province three Paleoproterozoic tectonic provinces (Karelia, Norrbotten and Kola) are recognized, Fig. 4. Crustal provinces in Finland; for descriptions, and the Svecofennian Crustal Province is represented see Table 4 and Chapter 4. by the Central Finland and Southwestern Finland provinces. The division of tectonic provinces is summarized in Table 5, and more detailed province Karelia, (2) Norrbotten and (3) Kola (Figs. 5 and 6; descriptions can be found in Chapter 4. Table 5). Regarding the Paleoproterozoic tectonic provinces, The nature of the Norrbotten and Kola Tectonic here we primarily follow the overall evolutionary Provinces has not been finally resolved (see Fig. models developed in Lahtinen et al. (2005) and 5 and the suture zone descriptions in Chapter 4). Lahtinen & Huhma (2019), as summarized in Figure Nonetheless, according to the applied tectonic 5. The crustal-scale extension and the episodic model, the provinces represent active tectonic blocks rifting of the Karelia Craton from ca. 2.45 Ga to (ATBs) that rifted from the Karelia Craton at ca. 1.95 Ga is manifested by the abundance of mantle- 2.1–2.0 Ga ago. A repeated rifting stage occurred derived mafic dyke swarms; craton break-up and within the pre-existing passive margin. Extreme continental margin formation eventually occurred thinning of the continental crust led to a marginal at 2.1–2.06 Ga (Vuollo & Huhma 2005, Hanski & basin locally floored by the exhumed Archean lith- Huhma 2005, Huhma et al. 2018). The origin of the ospheric mantle, transected by sheeted mafic dykes Paleoproterozoic tectonic provinces is directly linked with ages around 1.97–1.95 Ga (Peltonen 2005 and to the rifting history, and the three tectonic prov- references therein). The province descriptions are inces within the Archean Crustal Province are (1) presented in Chapter 4 and summarized in Table 5.

48 Geological Survey of Finland, Bulletin 412 Classification of regional-scale tectonic map units in Finland

Departed (unknown) Archean Block Kola Block (ATB) ? Norrbotten Block (ATB) ? Iisalmi-Pudasjärvi ATB Karelia Craton New Continent

Stable craton Rifted margin – Passive continental margin - Foredeep Cratonization Central Finland ATB

Early formation of the Arc Complex SW Finland ATB

Svecofennia Arc Complex

Fig. 5. A simplified diagram based on the overall tectonic model (see also Fig. 3) showing theactive tectonic block (ATB) configuration and generation of the corresponding tectonic provinces. Lateral accretion and the assembly of the new continent marks the end of the ATB life span.

Table 5. Division of tectonic provinces in Finland and a summary of their characteristics (see also Chapter 4).

TECTONIC Pre-collision ATB life span Concise main lines of tectonic history Boundaries PROVINCE precursor (Ga) (in Finland; (ATB) see Table 6)

Karelia Rifted Karelia (2.6)–2.1–1.9 A large continental block cratonized ca. 2.6 Ga R–L Suture (in the Province> Craton >break-up of craton (ca. 2.1–2.05 Ga) SW) >development of continental margins Kautokeino– >repeated rifting stage (ca. 1.97 Ga) Muonio–Tornio >subduction >collisions (ca. 1.9 Ga) >foreland Suture (in the W) Pechenga–Imandra– Varzuga Suture (in the NE)

narrow proto-oceanic basin >closure without Suture (in the NE); Subprovince Block subduction in collision (1.91 Ga) R–LS (in the SE)

Norrbotten Norrbotten 2.1/(1.97)–1.91 Break-up from Karelia Craton (ca. Kautokeino– Province Block 2.1? Ga) >formation of (incipient?) ocean basin Muonio–Tornio >subduction to the W >major collision Suture (in the E) (1.91 Ga)

Kola Province Kola Block ca. 2.0–1.91 Break-up from Karelia Craton (ca. 2.0? Ga) > Pechenga–Imandra– formation of an ocean basin >subduction to the Varzuga Suture (in SW underneath the Karelia Craton theSW) >collision (1.91 Ga)

Central Finland Central >1.92–1.91 Formation of the arc collage (prior to 1.92 Ga; Raahe–Ladoga Province Finland see description) >subduction to the SW >lateral Suture (in the NE) Arc Collage accretion to the Karelia Craton (1.91 Ga)

Southwestern Southwestern >1.90–1.88 Formation of the arc collage (see description) > Bothnia–Pirkanmaa Finland Finland Arc double-vergent subduction > lateral accretion to Suture (in the N) Province Collage the previously accreted Central Finland Arc Collage (1.88 Ga)

49 Geological Survey of Finland, Bulletin 412 Jarmo Kohonen, Raimo Lahtinen, Jouni Luukas and Mikko Nironen

Several tectonic models have been presented for the Svecofennian Orogeny in Fennoscandia (e.g., Gaál & Gorbatschev 1987, Nironen 1997, Lahtinen et al. 2005, 2009) and within a broader context (e.g., Bogdanova et al. 2015). The complexity of Svecofennian tectonic evolution leads to compli- cations in the definition of tectonic provinces. The identification of individual active tectonic blocks and the spatial definition of major collisional boundaries between these is a challenging task (e.g., Nironen 2017a). The reason may be either extensive magmatic, structural and metamorphic overprinting or, alternatively, syntectonic orocline buckling along the collision zones, as suggested by Lahtinen et al. (2014, 2017). In this exercise, we follow the main lines of the model presented by Lahtinen et al. (2005). According to the model, Svecofennian tectonic evolution involves colliding island arcs, micro- continents, reversing subduction zones and a late orogenic collapse. The microcontinent–arc collage origin for the Svecofennian Province implies the existence of collision zones (sutures) within the orogen. The Central Finland Tectonic Province (Table 5 and Fig. 6) represents an arc collage, consisting of a continental fragment (Keitele microcontinent) and an attached arc (Lahtinen et al. 2005). The arc collage collided around 1.91 Ga with the Karelia Craton. The younger ATB corresponding to the Southwestern Finland Tectonic Province represents the development of another juvenile arc collage, which finally laterally accreted to the previous Central Finland Arc Fig. 6. Tectonic provinces in Finland. The numbers Collage ca. 1.88 Ga ago along a double-vergent sub- refer to the province boundaries: (1) the Raahe–Ladoga Suture (R–LS); (2) the Jormua–Outokumpu Suture duction zone. For the more comprehensive province (J–OS) separating the Iisalmi–Pudasjärvi Subprovince descriptions, see Chapter 4. from the Karelia Province; (3) the Kautokeino–Muonio– Tornio Suture (K–M–TS); (4) the Pechenga–Imandra– Varzuga Suture (P–I–VS); (5) the Bothnia–Pirkanmaa 3.3.2 Suture zones Suture (B–PS).

The term ‘suture’ (see Part 1 for discussion of the term) is used as part of the name for all the tectonic province boundaries; a summary of their characteristics is presented in Table 6.

3.4 Structural provinces

3.4.1 Division and boundaries of structural imity of the suture zone. The division of structural provinces provinces is based on linking of the observed overprinting structural features to the major collision Major collision zones inevitably have a major impact zones (see Part 1). It is essential to note that the on regional structural patterns, and the greatest structural provinces are not defined by the dominant intensity of deformation is expected in the prox- structural feature, but by the observed structures link-

50 Geological Survey of Finland, Bulletin 412 Classification of regional-scale tectonic map units in Finland

Table 6. Characteristics of the tectonic province boundaries (compare to Table 2 in Part 1).

PROVINCE BOUNDARY Tectonic Nature Geological Tectonic Provinces; Lower Spatial Province Plate (LP) and Upper Plate – Location Contact Type (UP) – Nature – Width

Raahe–Ladoga Suture Collisional Cryptic suture LP: Karelia – Defined (R–LS) Continent/Arc zone UP Central Finland – Undefined – Wide zone

Jormua–Outokumpu Collisional Suture zone LP: Karelia in the NE – Well defined Suture (J–OS) Continent/Continent UP: Iisalmi–Pudasjärvi – Sharp/undefined (continent fragment; – Narrow zone no subduction)

Kautokeino–Muonio– Collisional Cryptic Suture LP: Karelia – Poorly defined Tornio Suture Continent/Continent zone UP: Norrbotten – Undefined (K–M–TS) – Narrow/wide zone

Pechenga–Imandra– Collisional Cryptic suture LP: Kola – Poorly defined/inferred Varzuga Suture (P–I–VS) Continent/Arc zone UP: Karelia – Undefined – Wide zone

Bothnia–Pirkanmaa Collisional Cryptic suture Southwestern Finland – Poorly defined/inferred Suture (B–PS) Arc/Arc zone Central Finland – Undefined (double-vergent subduction) – Wide zone

able to a certain collision zone. The provinces are may be proposed as a structural domain or other in many cases heavily overprinted by subsequent LT-FIN-SP map unit. deformation events, which are not shown but are partly recognizable as refolding and transposition 3.4.2 Paleoproterozoic structural provinces of the collision-related structural patterns. In this study we test the LT-FIN-SP approach The orogenic belt (orogen) corresponding to the and, as an example, present a province/subprov- Svecofennian Orogeny (see Chapter 2.5.2) extends ince-level division within the Karelia and Norrbotten far beyond the Svecofennian Crustal Province, as Tectonic Provinces. The Karelia Tectonic Province pro- the orogenic foreland is severely deformed along vides an ideal test bed for the structural province the collision zones. On practical level, the Figure approach, inasmuch as there is an actual need for 7 displays, for the first time, the assumed extent conceptual and spatial division of the ancient fore- and style of Svecofennian foreland deformation on land characterized by (1) variably deformed and a national scale. All the suture zones bounding or partly allochthonous cover sequences, (2) basement transecting the Archean Crustal Province have a con- blocks reactivated in Svecofennian crustal shorten- nection to the corresponding structural provinces and ing and (3) relatively intact basement areas. It is to the structural style on both sides of the suture still emphasized that the spatial definitions (extent zone. The Paleoproterozoic structural provinces with and boundaries) are preliminary and the descrip- a preliminary division into subprovinces are pre- tion of structural provinces will develop with future sented in Table 7. research. The current division of structural provinces is 3.4.3 Paleozoic Kilpisjärvi Structural Province presented in Figure 7. At this stage, the proposal only includes the collision-related Proterozoic and The map-unit terminology related to the Finnish Paleozoic structural provinces and their subprov- Caledonides is not well established. Korsman inces, but basically any area with structural fea- et al. (1997) termed the area on the NW side of tures significantly different from the adjacent areas the Caledonian frontal thrust as the ‘Caledonian

51 Geological Survey of Finland, Bulletin 412 Jarmo Kohonen, Raimo Lahtinen, Jouni Luukas and Mikko Nironen

Domain’ without any definition. Nironen et al. to Caledonian Orogeny (see Fig. 7 and Table 7). (2016) denoted the same area as ‘Allochthonous According to the LT-FIN principles (see Part 1), rocks of the Caledonides’. The Kilpisjärvi area rep- the area is referred to as the Kilpisjärvi Structural resents the frontal part of the thrust belt related Province.

Fig. 7. Structural Provinces and their relationships with the defined suture zones (see Tables 6 and 7; the province descriptions are presented in Chapter 4).

52 Geological Survey of Finland, Bulletin 412 Classification of regional-scale tectonic map units in Finland

Table 7. Division of structural provinces in Finland and summary of their characteristics (see Fig. 7 for locations, Chapter 4 for the province descriptions and Table 6 for the sutures). Abbreviations: TP (tectonic province), TSp (tectonic subprovince), A–P (Archean–Proterozoic), PP (Paleoproterozoic)

STRUCTURAL Characteristic structural features (1) Related tectonic event; (2) Tectonic PROVINCE (Related to the Svecofennian main collision setting during deformation; stage ca. 1.91–1.90 Ga) (3) Boundaries (in Finland)

Svecokarelia Overprinting structures within the Karelia TP; folding (1) Major, complex collision along the present Structural and pervasive foliation within the cover sequence; R–L Suture; closure of a narrow proto-oceanic Province> localized high-strain zones within the basement; basin along deformation intensity fading eastwards; the province Jormua–Outokumpu Suture; boundary marks the extent of structural overprinting (2) Foreland fold and thrust belt (see Subprovinces for more details) (peripheral); (3) R–LS (in the SW); see Fig. 7 and subprovince descriptions for the NE boundary

obduction of Jormua Ophiolite and other able degree of overprinting and indistinct structural fragments subcontinental lithosphere. grain in the proximity of the A–P boundary

Norrbotten–Lapland Overprinting structures within the Karelia TP; folding (1) Collision along the present K–M–T Suture; Structural Province and pervasive to indistinct foliation within the cover (2) Foreland fold and thrust belt (peripheral); sequence; E-vergent thin-skinned thrusts in W parts; major crustal shortening in the W; only minor current foliation trend variable; deformation intensity shortening in the easternmost parts waning towards the E and intense deformation only (3) K–M–TS (in the W); see Fig. 7 and along reactivated basement fault zones; the eastern description for the other boundaries boundary marks the extent of structural overprinting.

Muonio–Ropi Overprinting collision-related structures within the (1) Collision along the present K–M–T Suture; Structural Norrbotten TP; main structural trend follows the N–S (2) Retroarc (upper plate) fold and thrust Province orientation of the adjacent suture; alternating base- belt on the W side of the K–M–T Suture ment inliers and PP cover outliers are characteristic; (3) K–M–T Suture (in the E); see Fig. 7 and foliation weakly developed in basement TTG litholo- description for the NW boundary gies; deformation intensity waning towards the NW. (Detailed structural studies scarce)

Hetta–Jergul E-vergent thrust faults in the western and central (1) Collisions along the present K–M–T Suture Structural parts; some parts of the ‘basement block’ are rela- (in the W) and along the V–I Suture (far in Province tively intact (?); the margins on both sides sheared the NE) (‘Hetta–Jergul Block’) due to overlying cover thrusts. (The area is poorly (2) Tectonic setting undefined; block exposed and detailed knowledge is limited) between K–M–TS and Kola collision-related thrusts (see description in Chapter 4) (3) see Fig. 7 and description for the boundaries

53 Geological Survey of Finland, Bulletin 412 Jarmo Kohonen, Raimo Lahtinen, Jouni Luukas and Mikko Nironen

Table 7. Cont.

Kola–Lapland Overprinting structures within the Karelia Tectonic (1) Complex collision along the present P–I–V Structural Province; variable intensity of foliation and folding Suture (in the NE) Province> styles in different subprovinces; southern province (2) Retroarc (foreland) fold and thrust belt; boundary marks the extent of structural overprinting upper plate deformation of continental arc (see Subprovinces for more details) and foreland further in the S. (3) V–I Suture (in the NE); see Fig. 7 and Sodankylä subprovince description for the SW boundary

Related to the Scandian phase of the Caledonian Orogeny (ca. 425–400 Ma)

Kilpisjärvi Caledonian thrust sheets and overprinting structures (1) Collision (further in the W) related to the Structural within the foreland cover rocks below the frontal Scandian phase of the Caledonian Orogeny. Province ramp (detachment). Structural trend parallel to the (2) Foreland fold and thrust belt (peripheral) (Finnish part of the SW–NE strike of the Caledonian thrust front. (3) Extent is the defined by overprinting of the Caledonian Thrust cover Belt)

3.5 Discussion and recommendations

3.5.1 Applicability of the (LT-FIN) province division tal/tectonic/structural provinces support the identi- in Finland fication of different aspects presented in tectonic development models and other relevant information. Finnish geological maps and scientific articles are The LT-FIN system provides tools to handle complex rich in tectonic map unit terminology, and the mini- tectonic concepts systematically in the arrangement mal consistency has been a source of much confu- and characterization of large-scale map units. Part sion. Most often, the tectonic terms appear in map of the proposed system may be applicable elsewhere, legends (e.g., Korsman et al. 1997, Koistinen et al. especially in Fennoscandia and in other Precambrian 2001, Nironen et al. 2016) and in article introduc- shield areas with long evolutionary histories involv- tions (e.g., Lehtinen et al. 2005) without any sup- ing superimposed orogens. porting terminological information. The current The isotope geological research (e.g., Vaasjoki work both improves the situation and demonstrates et al. 2005, Huhma et al. 2011) has provided a reli- the complexity of the tectonic terminology. able overall picture of the continental crustal ages, LT-FIN province classification was straightfor- and the main lines of the crustal growth history in ward to apply to major regional-scale tectonic map Finland are widely agreed. Consequently, the crus- units in Finland. The LT-FIN definitions for thecrus - tal province division is not significantly dependent

54 Geological Survey of Finland, Bulletin 412 Classification of regional-scale tectonic map units in Finland on the tectonic models presented. This is the fun- the definition of other classes such as igneous, damental difference compared to the concept of sedimentary, metamorphic and even metallogenic a tectonic province. The crustal provinces are also provinces. The definition and characterization of spatially apparent; the subprovinces are less so, the classes would be according to the principles and but conceptually necessary and uncomplicated to examples presented in this paper. comprehend. The division of major the Precambrian map The definition of thetectonic provinces is coupled units has been in Finland under a major change; to the evolution model presented by Lahtinen et al. the lithostratigraphic/lithodemic unit system was (2005), but the description of the main collision implemented (2007–2017) and the tectonostrati- zones (suture zones) connects the province bound- graphic division is progressing (Luukas et al. 2017, aries to real geological features. Modern geologi- Luukas & Kohonen 2021; this volume). Concerning cal map portray involves the tectonic history (e.g., the lithotectonic units, igneous provinces are not Korsman et al. 1997, Nironen et al. 2016), and one defined at this stage to avoid a premature judge- practical advantage of tectonic province division ment concerning the need for the new category, but relates to legend compilation and arrangement of some igneous features with potential for igneous the other map units. Lithostratigraphic correlation provinces can be listed: can be limited to provinces (map units) sharing a • Mafic dyke swarms (2.5–1.97 Ga) and related common tectonic history; correlation between units intrusions within the Karelia Province representing separate ATBs is in most cases not • Appinites in Lapland (1.80–1.79 Ga) meaningful. • Post-tectonic granites in Lapland Regional structural mapping is different from (ca. 1.80–1.78 Ga) lithological mapping, as the structural domains • Rapakivi granites and associated mafic dykes overlap each other, the boundaries may be grada- (ca. 1.65–1.54 Ga) tional or diffuse and, in some cases, the distinc- • Lamprofyres and kimberlites of various ages tion between observation (of structural features) and interpretation (genesis, correlation of struc- The metamorphic map of Finland (Hölttä & tures) is ambiguous. The recognition of different Heilimo 2017), the different metallogenic maps structural domains with characteristic structural (e.g., Saltikoff et al. 2006, Eilu et al. 2009, Eilu features is becoming a standard convention. The 2012) and mineral resource and potential endow- improved portrayal of regional structural features ment estimation compilations (e.g., Rasilainen et (e.g., high-strain vs. low-strain domains, extent of al. 2010, 2016), could easily been developed towards overprinting structures) would offer an additional a more systematic province classification, if found component for geological interpretations from appropriate and applicable. nationwide compilations to detailed modelling. Systematic regional characterization of the 3.5.3 Terminological comments and structural provinces, subprovinces and domains is recommendations both methodologically and conceptually in an initial stage. Structural research and interpretation 3.5.3.1 Time–stratigraphic terms and have proven capable in resolving the evolution of terminology of orogenies complex areas (e.g., Central Lapland belt, Vihanti– The relationship between the terminology related Pyhäsalmi–Rautalampi belt, Lapland granulite to orogenies (‘orogeny’; orogenic cycle’; orogenic belt). We believe that further development and sys- phase’; see Neuendorf et al. 2005), formal chron- tematic subdivision of the structural provinces would ostratigraphy (eonothems, erathems, systems) and have great potential to support regional mapping local, informal, time–stratigraphic terminologies and modelling in Finland. is complex as such and the historical legacy terms further complicate the issue (see Laajoki 1986, 1989, 3.5.2 Potential new categories and extension of Gaal & Gorbatschev 1987, Strand et al. 2010). In the the LT-FIN system Precambrian of Finland, one major terminological challenge relates to the term ‘Svecofennian’ (cf. Lithotectonic map units might also be a suitable tool Laajoki 1989). The term ‘Svecokarelian Orogeny’ for other types of geological provinces (see Table was widely used in the older Finnish geological lit- 1), and the system is open to extension through erature (e.g., Simonen 1980). Gaál & Gorbatschev

55 Geological Survey of Finland, Bulletin 412 Jarmo Kohonen, Raimo Lahtinen, Jouni Luukas and Mikko Nironen

(1987) questioned the concept as misleading, spite of this, the proposed names are seen as appro- and in the latest comprehensive review of the priate and applicable. Crustal provinces are primar- Finnish bedrock (Lehtinen et al. 2005), the term ily defined by the geological age of the continental ‘Svecokarelian’ was completely abolished and crust, and the link to time–stratigraphic terms is replaced by Svecofennian Orogeny. justified. Most importantly, the selected names The Svecofennian Orogeny is generally brack- follow the common practice applied and de facto eted between 1.9–1.8 Ga (Huhma 1986, Patchett accepted in Finland (e.g., Gaál & Gorbatschev 1987; & Kouvo 1986, Gaál & Gorbatschev 1987). The see the crustal province descriptions for details). orogenic phase has previously been subdivided As an informal time–stratigraphic (system/ into early Svecofennian (1.91–1.86 Ga) and late period) term, Svecofennian is in common use for Svecofennian (1.83–1.80 Ga) periods (Saalmann et the whole of Finland, corresponding to the sys- al. 2009, Nironen & Mänttäri 2012) separated by an tem developed during and after the major collision intraorogenic period (Bergman et al. 2008, Lahtinen and amalgamation stage (at ca. 1.9 Ga). The earlier & Nironen 2010, Nironen 2011, Väisänen et al. 2012). subdivisions presented for the Svecofennian either Nonetheless, within the Svecofennian Crustal Province, reflect the pre-plate-tectonic paradigm (Sederholm the oldest rocks are around 1.93 Ga (Huhma et al. 1932, Simonen 1960, 1980, 1986) or only consider 2011), and a protocrust with an age of up to 2.0 Ga part of Finland (e.g., Williams et al. 2008, Saalmann has been envisaged (e.g., Lahtinen et al. 2005). et al. 2009, Nironen & Mänttäri 2012). For simplicity The authors do note that the proposed crustal and consistency, we propose within the Svecofennian province names, Archean Province and Svecofennian Province an informal, time–stratigraphic subdivi- Province, do not follow best practices by pairing a sion into Lower, Middle and Upper Svecofennian (see formal term, ‘Archean’ (Eon), with a local term, Fig. 8). In order to avoid further confusion, it is ‘Svecofennian’. Furthermore, the use of chron- noted that in the division proposed for central ostratigraphic terms (e.g., Archean) and the adjecti- Fennoscandia by Kousa et al. (2000), their Lower val form endings with the -ian (e.g., Svecofennian) and Upper Svecofennian respectively correspond referring to time–stratigraphy is in general not rec- to the Lower and Middle Svecofennian in Figure 8. ommended in unit names (see Strand et al. 2010). In

Svecofennian Province Archean Province IUGS 1800 Ma Upper Svecofennian Svecofennian 1860 - 1800 Svecofennian Orogeny 1900 - 1800 Middle Svecofennian 1900 - 1860 1900 Ma Early evolution of the Kalevian* Orosirian Svecofennian crust 1960 – 1900

Svecofennian Lower Svecofennian 2000 - 1900

Ludikovian* 2000 Ma 2060 – 1960

Lapland-Kola Orogen Karelian 2100 Ma Jatulian* Rhyacian Svecokarelia Orogen (+ suborogens) 2300 Ma 2500 Ma

*see Hanski & Melezhik (2012) Fig. 8. GTK-preferred time–stratigraphic terminology (in bold and italics) within the Archean and Svecofennian Crustal Provinces in Finland. The suggested orogen names (in bold and italics) referring to spatial orogenic belts are given within the red frame.

56 Geological Survey of Finland, Bulletin 412 Classification of regional-scale tectonic map units in Finland

3.5.3.2 Crustal, tectonic and structural provinces evolving new continent, not to the Archean Crustal in relation to orogens Province. The relationship between the provinces (CP, TP Appropriate general usage of ‘paleoterms’ is and SP) and the term orogen (or ‘orogenic belt’; also briefly discussed. One example is the Karelia see Neuendorf et al. 2005) is not straightforward, Craton, an ancient continent with a life span from either. An orogen is defined as an entity that has cratonization (ca. 2.6 Ga) to the major collision been subjected to deformation during an orogeny ca. 1.9 Ga ago. In present-day terminology, the (orogenic cycle). Orogeny is the process by which the Fennoscandian Shield is part of the East-European structures within fold-belt mountainous areas were Craton. The use of the term ‘Karelia Craton’ as a formed (Neuendorf et al. 2005), and the time span geological map unit (current part of the solid Earth) is accordingly the time of major deformation. The can be very confusing for a reader unfamiliar with Svecofennian Orogeny (ca. 1.9–1.8 Ga) is an example domestic naming traditions. Other paleoterm exam- of an orogenic cycle. An orogen is defined via the ples are ‘Karelia continental margin’ (ca. 2.1–1.9 concept of orogeny, and the regional extent of the Ga), ‘Savo Arc’ (ca. 1.95–1.91 Ga). The usage of resultant major deformation is critical. Svecofennian paleoterms in reconstructions, models and expla- deformation extends to the Karelia and Norrbotten nations is necessary and essential, but a mixture of Tectonic Provinces and the orogen is thus larger than the defined present-day geological map unit ter- the Svecofennian Crustal Province; we consider all the minology and paleoterms is often confusing and deformation events within the whole area as parts even misleading. of the Svecofennian Orogeny. The same applies in reverse. For example, the The major collision zones along margins of the term Fennoscandian Shield basically refers to an rifted Karelia Craton are denoted as boundaries of tec- area defined as a present-day map unit. The term tonic provinces (Central Finland, Norrbotten, Kola) (see is only valid in describing the present extent of Figs. 5 and 6). The orogenic belt (orogen) termi- exposed crystalline rocks (according to the defi- nology is not part of the LT-FIN map unit system, nition of the term ‘shield’). The shield exhumed but some remarks are presented. For historical rea- gradually during the Phanerozoic (e.g., Kohonen & sons (the original concept of the ‘Svecokarelides’; Rämö 2005), and in Precambrian reconstructions Simonen 1980) and for clarity (see discussion by (e.g., supercontinent assembly, paleomagnetic Laajoki 1989), the term Svecokarelia Orogen, instead reconstructions), other terms, such as ‘Baltica’, are of ‘Svecofennia Orogen’, is here suggested for the more appropriate. area corresponding to the Svecofennian Orogeny in western areas (Fig. 8). The term Lapland–Kola 3.5.3.4 Summary of recommendations Orogen has long been in use for the northeastern The division and definition of provinces, the sug- segment (see Daly et al. 2006, Lahtinen & Huhma gested informal time–stratigraphic terminol- 2019 and references therein). ogy and the revised orogen (orogenic belt) names To conclude, the extent of the Svecokarelia Orogen should provide a sufficient toolbox in Finland for comprises the entire Svecofennian Crustal Province the description of Paleoproterozoic geological together with the Svecokarelia and Norrbotten– evolution in space and time. The traditional terms Lapland Structural Provinces. The Finnish part of ‘Svecofennides’ and ‘Svecokarelides’ (cf. Simonen the Lapland–Kola Orogen consists of the Northern 1980) are nearly synonymous with the Svecokarelia Lapland Crustal Subprovince and Sodankylä Structural Orogen. The duplication of key terms potentially Subprovince (see Table 3 and Figs. 4 and 7). creates misunderstanding in the present plate tectonic context. Consequently, we suggest the aban- 3.5.3.3 Present-day map units in relation to donment of the following traditional but nowadays paleoterms vague or overlapping (*marked) terms: All the lithotectonic units, like geological map units • *Svecokarelian Orogeny; replaced by Sveco in general, represent current parts of the solid Earth fennian Orogeny; (see above) identified by their geological characteristics. Therefore, • *Svecofennides, *Karelides; dismissed; the caution is needed when transferring these terms underlying concept is unclear and outdated out of the original spatial context. For example, • *Svecokarelides; in a tectonic context replaced the Archean igneous activity added material to the by Svecokarelia Orogen (see above); the term

57 Geological Survey of Finland, Bulletin 412 Jarmo Kohonen, Raimo Lahtinen, Jouni Luukas and Mikko Nironen

‘Svecokarelides’ is appropriate in a paleogeo- Improved preciseness regarding the stand- graphic context for the ancient mountain chain; ard map unit terminology and terms referring to e.g., ‘…the denudation of the Svecokarelides…’ ancient reconstructions (paleoterms) is recom- • *Svecofennidic, *Svecokarelidic; dismissed, mended. Finally, it would be advantageous if the replaced by Svecofennian (see above) term ‘belt’ was used in the future only for geologi- • *Karelidic; dismissed, replaced by Karelian (see cal regions dominated by supracrustal rocks, with- above) out any stratigraphic connotations. The lithodemic • *Svionian, *Bothnian; dismissed, replaced in names (e.g., ‘Häme migmatite suite’ instead of informal time–stratigraphic terminology by ‘Häme belt’) would in most cases be more appro- Lower and Middle Svecofennian priate and accurate in most geological discussions.

4 REGIONAL-SCALE TECTONIC MAP UNITS IN FINLAND: DESCRIPTION*

*This description will be maintained and updated as part of the Finstrati (GTK Digital Lexicon of Geologic Units)

4.1 Crustal provinces in Finland

4.1.1 Archean Province 4.1.1.1 Central Karelia Subprovince • Definition: • Definition: – A province characterized by Neoarchean ages – A crustal province characterized as a whole by and a different tectonic history compared to Archean crust the adjacent areas – Rank (LT-FIN-CP): Province; no upper rank – The Finnish part of a larger province extending – Former names for the approximately corre- to Russia in the East sponding map unit: – Rank (LT-FIN-CP): Subprovince of the Archean – Archean Domain (Gaál & Gorbatschev 1987, Province Vaasjoki et al. 2005) – Former names for the approximately corre- – Karelian Domain (Korsman et al. 1997) sponding map unit: – Archean Crustal Domain (Sorjonen-Ward & – Ilomantsi Terrain (Sorjonen-Ward 2006) Luukkonen 2005) – Ilomantsi complex (the Finnish part of the • Geological age of major continental crust forma- Central Karelia subprovince; Hölttä et al. tion: 2.83–2.70 Ga; range 3.5–2.6 Ga 2012) • Boundaries: see Raahe–Ladoga Suture – Central Karelia Subprovince (tectonic sub- • Description: province of Nironen 2017a) – Composition: • Geological age of major continental crust forma- – Plutonic TTG with subordinate supracrus- tion/reworking: 2.74–2.72 Ga; range 2.76–2.6 Ga tal belts having corresponding depositional • Boundaries ages – Poorly defined both conceptually and spatially – Genesis: – Tectonic nature of the boundaries: Undefined – A result of Archean orogenic processes. – Contact type: Undefined lithogenetic contact Details of the orogenic history are poorly – Spatial features: (1) Location – poorly known. defined; (2) Nature – gradational; (3) Width– – Fully cratonized prior to 2.5 Ga. undefined – One continental block prior to the Paleo • Description: proterozoic break-up – Composition: – Key references: Gaál & Gorbatschev 1987, – Plutonic TTG with abundant sanukitoids; Sorjonen-Ward & Luukkonen 2005, Hölttä supracrustal belts with depositional ages 2012 comparable to the adjacent plutonic rocks. – Genesis: – Details of the orogenic history are poorly known.

58 Geological Survey of Finland, Bulletin 412 Classification of regional-scale tectonic map units in Finland

– Represents a short Neoarchean crustal – Genesis: growth period – Both the tectonic history behind the repeated – Key references: Hölttä et al. 2012 crustal reworking and the detailed age pattern of the subprovince are poorly known 4.1.1.2 Central Lapland Subprovince – Key references: Huhma 1986, Corfu & Evins • Definition: 2002, Niiranen et al. 2005, Ahtonen et al. 2007, – A province characterized by reworked Archean Lahtinen et al. 2018 crust, recycled and enriched by juvenile material in various Paleoproterozoic stages 4.1.1.3 Northern Lapland Subprovince – Several phases of rift-related mafic or • Definition: bimodal magmatism (ca. 2.4 – 2.1 – 1.98 Ga) – A crustal province with Archean crust char- – Norrbotten–Karelia collision-related plu- acterized by episodic Paleoproterozoic crustal tonic rocks (ca. 1.88 Ga) and late-orogenic growth manifested by both synorogenic (juve- (1.84–1.79) granitoids nile; 1.94–1.91 Ga) and late orogenic (1.90– – Rank (LT-FIN-CP): Subprovince of the Archean 1.89) granitoids Province – Rank (LT-FIN-CP): Subprovince of the Archean – Former names for the approximately corre- Province sponding map unit: – Former names for the approximately corre- – Central Lapland Granitoid Complex (CLGC; sponding map unit: numerous authors); the term is now in use – Lapland Granulite Belt & Inari Area (e.g., for a lithodeme (a complex consisting of Hanski & Huhma 2005) several igneous suites; see FinstratiKP) – Inari arc (Huhma & Meriläinen 1991) • Geological age of major continental crust • Geological age of major continental crust reworking: 1.89–1.79 Ga; range 2.9–1.77 Ga formation/reworking: 1.98–1.89 Ga; range • Boundaries (2.8–1.77 Ga) – Western boundary: see Kautokeino–Muonio– • Boundaries Tornio Suture – Northeastern boundary: see Pechenga– – Other boundaries are defined by the abundance Imandra–Varzuga Suture of Paleoproterozoic granitoids – Southern boundary coincides with the south- – Tectonic nature of the boundaries: Undefined ern margin of the Lapland Granulite Belt – Contact types: (1) Igneous intrusive contact, – Southernmost enderbite sills (ca. 1.92 Ga) (2) Undefined lithogenetic contact within high-grade gneisses – Spatially, boundaries are arbitrary and poorly – Archean crust underlying the granulite belt defined (partly due to poor exposure) is inferred without any direct evidence – Spatial features: (1) Location – poorly – Tectonic nature of the boundary: Undefined defined; (2) Nature – undefined (or variable); – Contact type: Faulted contact (3) Width – undefined – Spatial features: (1) Location – defined; (2) • Description: Nature – gradational to sharp; (3) Width – – Composition: narrow zone – Various types of granitoids and migma- • Description: tites; paragneiss inclusions; some outliers – Composition: of Paleoproterozoic quartzites; the only – Mainly consists of reworked Archean crust larger area with parent unit lithology is the and limited preservation of Paleoproterozoic Suomujärvi complex in the east; for details juvenile crust; two compositionally different of both the lithological composition and the parts: the Inari area and Lapland Granulite age pattern, see Lahtinen et al. (2018) Belt. – The dimensions and volume of the – Inari area (see Fig. 8 for location) Proterozoic granitoids are difficult to esti- – Paragneisses and amphibolites are mate; the gentle and locally nearly horizon- the dominant Archean rock types; tal structures may affect the current map compared to the parent unit, the extent of granitoids. proportion of TTG rocks is minor

59 Geological Survey of Finland, Bulletin 412 Jarmo Kohonen, Raimo Lahtinen, Jouni Luukas and Mikko Nironen

– Paleoproterozoic rocks include – Genesis: plutonic rocks from gabbros to – A result of crustal growth during the tonalites and granodiorites; quartz- complex Svecofennian Orogeny plausibly feldspar gneisses, paragneisses and involving a collage of several volcanic arc mafic metavolcanics; for details and complexes (e.g., Lahtinen et al. 2005). the age pattern, see Huhma (2019) – Several tectonic evolution models have and Lahtinen & Huhma (2019). been presented, but the details of the crus- – Lapland granulite belt (see Fig. 8 for tal growth history are not well constrained location) (cf. Nironen 1997, Lahtinen et al. 2005, – High-grade garnet-sillimanite Saalmann et al. 2009, Lahtinen et al. 2015b). gneisses with Proterozoic sedimen- – The province was fully cratonized prior to tary protoliths, cordierite-bearing 1.65 Ga (Pokki et al. 2013). diatexites; abundant norite and – Key references: Lahtinen et al. 2005, Pajunen enderbite sills. et al. 2008, Nironen 2005, 2017, Hölttä et al. – Genesis: 2019 – Subduction-related magmatism at the margin of the ancient Karelia Craton. Archean 4.1.2.1 Northern Svecofennia Subprovince crust was affected by subduction-related • Definition: (1.98–1.91 Ga) magmatism resulting in – A crustal subprovince characterized by pre- juvenile crustal segments (Lahtinen & dominantly older plutonic ages compared to Huhma 2019); details of the crustal growth adjacent Svecofennian areas and the parent history are poorly known. unit as a whole – Key references: Meriläinen 1976, Barbey et al. – Rank: Subprovince; subclass of the Sveco 1984, Berthelsen & Marker 1986, Gaál et al. fennian Province; no lower ranks 1989, Korja et al. 1996, Daly et al. 2006, Tuisku – Former names for the approximately corre- et al. 2006, 2012, Cagnard et al. 2011, Huhma sponding map unit: 2019, Lahtinen & Huhma 2019 – Savo Schist Belt (Lahtinen 1994) – Primitive arc complex of central Finland 4.1.2 Svecofennian Province (Korsman et al. 1997, Vaasjoki et al. 2005) – Savo belt (e.g., Lahtinen et al. 2005) • Definition: • Geological age of major continental crust growth: – A province characterized as a whole by Paleo 1.93–1.91 Ga; range 1.93–1.79 Ga proterozoic crustal ages • Boundaries – Rank (LT-FIN-CP): Province; no upper ranks – Northeastern boundary: see Raahe–Ladoga – Former names for the approximately corre- Suture sponding map unit: – Southwestern boundary is very indistinct due – Svecofennian Domain (Gaál & Gorbatschev to intense deformation and later intrusive 1987, Korsman et al. 1997, Kähkönen 2005, rocks Lahtinen et al. 2005) – Tectonic nature of boundary: undefined – Svecofennia Province (Tectonic Province by – Contact type: undefined lithogenetic contact Nironen 2017a) – Spatial features: (1) Location – inferred; (2) • Geological age of major continental crust forma- Nature – gradational (?); (3) Width – wide tion: 1.90–1.87 Ga; range 1.93–1.77 Ga zone or undefined • Boundaries: see Raahe–Ladoga Suture • Description: • Description: – Composition: – Composition: – Lithology is variable, mainly consisting of – Dominantly consists of plutonic granitoid different ortho- and paragneisses. Typical complexes (granodiorite, tonalite, granite) lithologies include gneissic tonalities with and variable amounts of supracrustal belts cogenetic felsic volcanics, paragneisses with and enclaves with corresponding deposi- variable protoliths and various metavolcanic tional ages rocks.

60 Geological Survey of Finland, Bulletin 412 Classification of regional-scale tectonic map units in Finland

– Genesis: – Granite-migmatite zone of Southern Fin – A result of early Svecofennian evolution; land (Mäkitie et al. 2019) represents the crustal growth preceding • Geological age of major continental crust re‑ the major collision along the Raahe–Ladoga working: 1.83–1.80 Ga; range (1.90–1.78 Ga) Suture. • Description: – The original extent of the crustal element – Composition: corresponding to the Subprovince is highly – Largely like the parent unit; S-type granites speculative and granite-migmatites are characteristic – Key references: Kousa et al. 1994, 2013, Lahti – Genesis: nen 1994, Lahtinen et al. 2015b, 2016 – The subprovince represents an extended period of crustal rejuvenation, referred to 4.1.2.2 Southern Svecofennia Subprovince as the late Svecofennian orogenic episode; • Definition: a rather stable intra-orogenic stage (ca. – A crustal subprovince characterized by pre- 1.86–1.83 Ga) was followed by an episode dominantly younger plutonic ages compared to of crustal reworking. adjacent areas and the parent unit as a whole – The tectonic cause of the crustal melting is – Rank: Subprovince; subclass of the Sveco controversial; both collisional and exten- fennian Province; no lower ranks sional (orogenic collapse) models have been – Former names for the approximately corre- presented (cf. Lahtinen et al. 2005, Kukko sponding map unit: nen & Lauri 2009). – ‘Southern Finland Migmatite Belt’ (several • Key references: Ehlers et al. 1993, Nironen 2005, authors with slightly different descriptions) Kurhila et al. 2005, 2011, Nironen & Kurhila 2008, – Late Svecofennian granite–migmatite zone Pajunen et al. 2008, Bergman et al. 2008, Lahti (Ehlers et al. 1993) nen & Nironen 2010, Nironen & Mänttäri 2012, – Granite Migmatite Belt (Pajunen et al. 2008) Hölttä et al. 2019

4.2 Tectonic provinces in Finland

4.2.1 Karelia Province – Karelian Craton (Lahtinen et al. 2005) – Karelia Block (Vaasjoki et al 2005) • Definition: – Karelian Domain (Sorjonen-Ward & – A tectonic province (LT-FIN-TP) characterized Luukkonen 2005) by (1) its tectonic history and (2) the nature of – Karelia Province (Nironen 2017a) the boundaries. • Description: – The pre-collision precursor (ATB) is the – Origin and tectonic history of the ATB: Rifted Karelia Craton; the continental block – The ancient continent was fully cratonized existing after the major break-up (ca. 2.1– prior to 2.5 Ga; origin of the Karelia Craton. 2.0 Ga) – Repeated intracratonic rifting stages were – Life span ca. 2.1–1.9 Ga (see below) finally followed (ca. 2.1–2.0 Ga) by the – The Rifted Karelia Craton acted as the core break-up of the continent (see Fig. 5); origin during the Paleoproterozoic collisional of the Rifted Karelia Craton, orogeny. – Marginal basins and passive continental – The tectonic province commenced ca. 1.9 Ga margins developed ago after the main collisions along the cur- – Margins of the Rifted Karelia Craton rent province boundaries. responded: – Boundaries: – in the SW and W to the approaching over- – Raahe–Ladoga Suture in the SW riding plate with the development of early – Kautokeino–Muonio–Tornio Suture in the W (foredeep) and late features of a tectonic – Pechenga–Imandra–Varzuga Suture in the NE foreland (of Svecofennian Orogen) – Rank (LT-FIN-TP): Province; no upper rank – in the NE to the subducting plate with – Former names for the approximately corre- the initiation of continental arc-type sponding map unit:

61 Geological Survey of Finland, Bulletin 412 Jarmo Kohonen, Raimo Lahtinen, Jouni Luukas and Mikko Nironen

magmatism (of the Lapland–Kola 4.2.1.1 Iisalmi–Pudasjärvi Subprovince Orogen) • Definition: – The main collisions occurred around 1.91 – A province (LT-FIN-TP) characterized by (1) Ga and also involved the precursor of the its tectonic history and (2) the nature of the Iisalmi–Pudasjärvi Subprovince (see below). boundaries. – Raahe–Ladoga Suture (R–LS) – The pre-collision precursor (ATB) is the – A result of continent/arc collision (Rifted Iisalmi–Pudasjärvi Block Karelia Craton/Central Finland Arc Collage); – life span ca. 1.97–1.91 Ga (see below) lower plate: Karelia (also see the alterna- – The tectonic subprovince was created in tive tectonic models) relation to the major collision ca. 1.91 Ga – A subducted slab steepened strongly at ago; see Raahe–Ladoga Suture above. a high angle and finally a shallow slab – Boundaries: breakoff occurred. – Raahe–Ladoga Suture in the WSW – Mantle–crust decoupling of the Archean – Jormua–Outokumpu Suture in the ENE lithosphere occurred; as a result, parts of – Rank (LT-FIN-TP): Subprovince of the Karelia the upper plate were partly buried beneath Province the eastern cratonic blocks and a ‘crocodile – Former names for the approximately corre- jaw’ geometry formed. sponding map unit: – The suture was severely affected by a defor- – Iisalmi Complex and Pudasjärvi Complex mation event followed by voluminous mag- (Vaasjoki et al. 2005, Lahtinen et al. 2005, matism at 1.88–1.87 Ga. Peltonen 2005) – As a result of the later deformation stages, – Iisalmi Block and Pudasjärvi Block (Vuollo the R–L Suture Zone is characterized by & Huhma 2005, Nironen 2017a) complex structures and late-stage strike- – Pudasjärvi–Iisalmi complex (Laajoki 2005) slip faults; deformation events continued • Description: until ca. 1.79 Ga – Origin and tectonic history of the ATB: – Former names for the approximately cor- – Major continent break-up (2.1–2.06 Ga) was responding zone: followed by a new extension stage and rift- – ‘Raahe–Ladoga Zone’ (several authors ing oblique to the continental margin. with slightly different descriptions); – The Iisalmi–Pudasjärvi Block (ATP) rifted the term has been used to mean both from the Rifted Karelia Craton some 1.97–1.95 (1) a suture, collision zone and (2) fault Ga ago. zone, zone of major reactivation (Raahe– – The basin between the blocks advanced to a Ladoga fault zone) proto-oceanic rift trough – Svecofennian fault zone (Hietanen 1975) – The Iisalmi–Pudasjärvi Block (ATP) was – Ladoga–Bothnian Bay Tectonic Zone forcefully amalgamated with the eastern (Gaál & Gorbatschev 1987) continental foreland along the Jormua–Outo – Raahe–Ladoga Geosuture (Ekdahl 1993) kumpu Suture in a collision ca. 1.91 Ga ago. – Archean–Proterozoic Collision boundary – Jormua–Outokumpu Suture (J–O S) (Lahtinen et al. 2015b) – The result of a basin inversion and forceful – Alternative models: closure of the narrow basin; a suture with – Karelia as the upper plate; Hietanen no subduction; geometrically lower plate: (1975), Gaál & Gorbatschev (1987), Ekdahl Karelia (1993) – Due to extension, lithospheric stretching – No collision – the provinces represent and extreme thinning of the continental exotic terranes juxtaposed along a major crust, the Archean subcontinental lith- strike-slip fault; Park et al. (1984), Park ospheric mantle was exhumed, and the rift (1985), Kontinen & Paavola (2006) axial zone was intruded by mafic plutons – Key references: Gaál 1990, Lahtinen 1994, and sheeted dykes (ca. 1.95 Ga). Kohonen 1995, Lahtinen et al. 2005, 2009, – The advanced rift basin was floored by 2015, 2016, Kukkonen et al. 2006, Sorjonen- Archean lithosphere (ultramafic rocks) upon Ward 2006 which the pillow lavas and clastic sedi-

62 Geological Survey of Finland, Bulletin 412 Classification of regional-scale tectonic map units in Finland

ments layered; the geometry of the basin – The Norbotten Block (ATP) rifted from the represented by the suture is poorly known, Karelia Craton during the major break-up but the present geometry might support a of the continent some 2.14–2.06 Ga ago; wedge-shaped rift narrowing towards the (see K–M–TS description for alternative north. models). – During the main collision (1.91 Ga), major – The basin between the active tectonic blocks crustal shortening took place, and as a advanced at least up to the incipient ocean result, the I–P Block was partly thrust over basin stage. the main craton (Rifted Karelia Craton) in the – The Norrbotten Block (ATP) was accreted to east. the eastern continental foreland block along – Obduction of the Jormua and Outokumpu the Kautokeino–Muonio–Tornio Suture in a Ophiolite Complexes occurred along the major collision ca. 1.91 Ga ago. present suture zone. – Kautokeino–Muonio–Tornio Suture – The suture was reactivated as a strike-slip (K–M–TS) shear zone after the collisional stage – Lower plate in collision: Karelia – Former names for the approximately cor- – The Norrbotten Block separated from the responding zone: Karelia Craton (see above). – Kainuu–Outokumpu zone (Ekdahl 1993) – Obduction of the ophiolites (Nuttio serpent- – Kajaani tectonic zone (Laajoki 2005) inite belt; Peltonen 2005) occurred together – Kainuu suture (Kontinen & Paavola 2006) with the Kittilä allochthon along the pre- – Alternative models: sent suture in collision-related crustal – No separation of Iisalmi–Pudasjärvi Block shortening from the Karelia Craton; ophiolites and – The suture zone was severely affected by associated supracrustal rocks thrusted voluminous magmatism at 1.88–1.87 Ga, over the Iisalmi Block from the WSW (the followed by younger sedimentary rocks klippe model without J–OS); Peltonen & (<1.88 Ga), and several deformation events Kontinen 2004, Kontinen & Paavola 2006 at 1.89–1.79 Ga. – Key references: Kontinen 1987, Kohonen 1995, – Former names for the approximately cor- Peltonen et al. 1998, Peltonen 2005, Peltonen responding zone: & Kontinen 2004, Lahtinen et al. 2015b – Baltic–Bothnian megashear (Berthelsen & Marker 1986) 4.2.2 Norrbotten Province – Pajala shear zone (Kärki et al. 1993) – Lapland–Norrbotten suture (Lahtinen et • Definition: al. 2015a) – A tectonic province (LT-FIN-TP) characterized – Alternative models: by (1) its tectonic history and (2) the nature of – Berthelsen and Marker (1986) interpreted the boundaries. that K–M–TS was formed as a result of – The pre-collision precursor (ATB) is the intraplate strike-slip movements (see Norrbotten Block also Skyttä et al. 2019). – Life span ca. 2.1–1.91 Ga (see below) – An intracontinental rift that subsequently – The tectonic province commenced after the inverted to a thrust and fold belt (Nironen collision of the Rifted Karelia Craton and the 1997) Norrbotten Block ca. 1.91 Ga ago – Key references: Berthelsen & Marker 1986, – Boundary is the Kautokeino–Muonio–Tornio Kärki et al. 1993, Nironen 1997, Lahtinen et Suture in the E al. 2005, 2015a – Rank (LT-FIN-TP): Province; no upper ranks – Former names for the approximately corre- 4.2.3 Kola Province sponding map unit: – Norrbotten Craton (Lahtinen et al. 2005) • Definition: – Norrbotten Province (Nironen 2017a) – A tectonic province (LT-FIN-TP) characterized • Description: by (1) its tectonic history and (2) the nature of – Origin and tectonic history of the ATB: the boundaries.

63 Geological Survey of Finland, Bulletin 412 Jarmo Kohonen, Raimo Lahtinen, Jouni Luukas and Mikko Nironen

– The pre-collision precursor (ATB) is the Kola – The pre-collision precursor (ATB) is the Block (life span ca. 2.0–1.91 Ga; see below) Central Finland Arc Collage (life span ca. 2.0– – The boundary in the SW is the Pechenga– 1.91 Ga; see below) Imandra–Varzuga Suture (see Tables 5 and 6) – The boundary in the SW is the Bothnia– – Rank (LT-FIN-TP): Province; no lower ranks Pirkanmaa Suture (see Tables 5 and 6) – Former names for the approximately corre- – The boundary in the ENE is the Raahe– sponding map unit: Ladoga Suture (see Tables 5 and 6) – Kola Peninsula Province (Gaál & Gorbat – The tectonic province was created by the col- schev 1987) lision of the Central Finland Arc Collage and the – Kola Block (Vaasjoki et al. 2005) Karelia Craton at ca. 1.91 Ga – Kola (crustal) domain (Sorjonen-Ward & – Rank: Province; no upper ranks Kola craton (Lahtinen et al. 2005) – Former names for the approximately corre- – Muurmansk craton (Daly et al. 2006) sponding map unit: – Lapland–Kola Province (Nironen 2017a) – Accretionary arc complex of central and • Description: western Finland (Korsman et al. 1997) – Origin and tectonic history of the ATB: – Western Finland Subprovince (Nironen – The Kola Block separated from the Karelia 2017a) Craton around 2.0 Ga (see alternative • Description: models) – Origin and tectonic history of the ATB: – The basin between the blocks advanced up – The nucleus of the Central Finland Arc to the oceanic basin stage. Collage (Keitele microcontinent) was a 2.1– – The Kola Tectonic Province was commenced 2.0 Ga old fragment of continental crust of in the collision of the Kola Block and Karelia unknown origin. Craton and ca. 1.91 Ga ago – Juvenile crust, with ca. 1.92 Ga age, within – Pechenga–Imandra–Varzuga Suture (P–I–VS) the Arc Complex indicates initial accretion – Lower plate in collision: Kola prior to 1.92 Ga. – Former names for the approximately cor- – The Central Finland Arc Collage (ATB) was lat- responding zone: erally accreted to the eastern Karelia Craton – Pechenga–Imandra–Varzuga collisional along the R–L Suture in collision ca. 1.91 Ga suture (Daly et al. 2006) ago (see description of RL–S for details). – Alternative models: – Key references: Lahtinen et al. 2005, 2015b, – Subduction towards the present NE under 2017, Korja et al. 2009, Nikkilä et al. 2016 the Lapland granulite belt has also been proposed (Barbey et al. 1984, Krill 1985, 4.2.5 Southwestern Finland Province Tuisku et al. 2006, 2012, Nironen 2017b), • Definition: which would imply that V–IS occurred in – A tectonic province (LT-FIN) characterized by a back-arc position and is not a suture. (1) its tectonic history and (2) the nature of the – Daly et al. (2006) proposed a model of boundaries. two opposite subduction systems within – The pre-collision precursor (ATB) is the closure of the Pechenga–Varzuga and Southwestern Finland Arc Collage (life span Lapland–Kola oceans. ca. 2.0–1.91 Ga; see below) – Key references: Barbey et al. 1984, Krill 1985, – The boundary in the N and E is the Bothnia– Daly et al. 2006, Tuisku et al. 2006, 2012, Pirkanmaa Suture (see Tables 5 and 6) Lahtinen et al. 2005, Nironen 2017b, Lahtinen – The tectonic province was commenced in & Huhma 2019 lateral accretion of the Southwestern Finland Arc Collage to the previously accreted Central 4.2.4 Central Finland Province Finland Arc Collage ca. 1.88 Ga ago. – Rank: Province; no upper or lower ranks • Definition: – Former names for the approximately corre- – A tectonic province (LT-FIN) characterized by sponding map unit: (1) its tectonic history and (2) the nature of the – Accretionary arc complex of southern Fin boundaries. land (Korsman et al. 1997)

64 Geological Survey of Finland, Bulletin 412 Classification of regional-scale tectonic map units in Finland

– Southern Finland Subprovince (tectonic sub- dips NE in the Bothnian Bay area (Korja province) (Nironen et al. 2017a) et al. 2002). • Description: – The suture was in the eastern part severely – Origin and tectonic history of the ATB: affected by granite magmatism (1.84–1.82 – The Southwestern Finland Arc Collage con- Ga) and deformation (1.83–1.77 Ga) during sists of juvenile crust of an arc complex the late Svecofennian orogenic episode. (1.90–1.88 Ga), possibly with an older (ca. – As a result of the later deformation stages, B– 2.0 Ga) continental fragment (Bergslagen PS is characterized by complex structures and microcontinent). late-stage dextral strike slip faults; deforma- – The Southwestern Finland Arc Collage moved tion events continued until ca. 1.79 Ga northwards in the southern side of the dou- – Former names for the approximately cor- bly vergent subduction zone responding concept: – With the closure of the ocean (ca. 1.88 Ga), – Southern Finland Conductor (Korja & the Southwestern Finland Arc Complex Hjelt 1993) accreted laterally to the previously accreted – (Southern boundary of) the Tonalite Central Finland Arc Complex. Migmatite Zone (Koistinen et al. 1996) – Bothnia–Pirkanmaa Suture (B–PS) – Vanaja detachment (Nironen et al. 2006) – In the model by Lahtinen et al. (2005), B–PS – Alternative models: represents the accretion of two arc com- – The models assuming continuous sub- plexes. Oceanic basin between the com- duction and crustal growth during the plexes closed as a result of double-vergent Svecofennian do not employ sutures subduction. within the Svecofennian Crustal Province – The nature of the original suture is poorly (e.g., Saalmann et al. 2009) known – The orocline model (2014) could indi- – Originally considered as accretion prism cate the occurrence of only one sub- between the Central Finland and South duction system later tightly buckled to western Finland Arc Collages. mimic double-vergent subduction zones – Geophysical data provide evidence for (Lahtinen et al. 2017). the suture; the E–W-trending electrical – Key references: Lahtinen et al. 2005, 2017, conductivity anomaly is almost vertical Väisänen & Skyttä 2007, Pajunen et al. 2008, down to 60 km depth in southern Finland, Skyttä & Mänttäri 2008, Saalmann et al. 2009 curves towards the Bothnian Bay, and

4.3 Structural provinces in Finland

4.3.1 Svecokarelia Structural Province – Tectonic setting of the unit: Foreland fold and thrust belt (peripheral) • Definition: – Rank (LT-FIN-SP): Province; no upper rank – A structural province (LT-FIN-SP) character- • Description: ized by (1) its structural features and (2) the – Characteristic structural features include tectonic setting. (1) thin-skinned deformation of the Paleo – The province is defined by structures related proterozoic cover and (2) basement involving to the major, complex collision along the deformation with associated overprinting of present R–L Suture ca. 1.91–1.90 ago. the Archean structures. – Overprinting structures within the Karelia – The eastern province boundary marks the Tectonic Province extent of the collision-related structural over- – Folding and pervasive foliation within the printing (see Subprovinces for more details) cover sequence – Svecofennian peak metamorphism was – Semiductile deformation with localized reached after the development of collision- high-strain zones within the basement; related structures overall overprinting fabric in the base- – The cover sequence typically displays low to ment granitoids weak or moderate. middle amphibolite facies (Hölttä & Heilimo 2017)

65 Geological Survey of Finland, Bulletin 412 Jarmo Kohonen, Raimo Lahtinen, Jouni Luukas and Mikko Nironen

– The overall metamorphic grade increases the metamorphic grade of cover rocks and in towards the west; migmatites are common Svecofennian reheating of the Archean base- in the proximity of the R–L Suture zone. ment; reason not known. • Nature of unit boundaries: see Subprovinces • Nature of unit boundaries: • Key references: Väyrynen 1939, Laajoki 1991, – Eastern boundary: 2005, Kohonen 1995 – Nature: Lithogenetic contact> Deformation boundary zone (Structural) 4.3.1.1 North Karelia–Kainuu Subprovince – Spatial features: • Definition: – Location: Poorly defined (with decreas- – A structural subprovince (LT-FIN-SP) char- ing intensity of structural overprinting; acterized by (1) its structural features and (2) the zonal nature of basement deformation the tectonic setting. complicates the definition) – The province is defined by structures related – Nature: Gradational to the major collision (ca. 1.91–1.90 Ga) and – Width: n/a closure of a narrow proto-oceanic basin – Western boundary: along the present Jormua–Outokumpu Suture – J–O Suture; see Table 6 – Tectonic setting of the unit: Foreland fold • Key references: Väyrynen 1939, Gaál et al. 1975, and thrust belt on the eastern side of the Koistinen 1981, Kontinen et al. 1992, Ward 1987, Iisalmi–Pudasjärvi Tectonic Subprovince Kohonen et al. 1991, Kohonen 1995, Laajoki 1991, – Rank (LT-FIN-SP): Subprovince; upper rank Kärki et al.1993, Laajoki & Tuisku 1990, Tuisku & Svecokarelia SP Laajoki 1990, Korja et al. 2006, Sorjonen-Ward – Informal name: North Karelia–Kainuu fold and 2006 thrust belt • Description: 4.3.1.2 Kuopio–Iisalmi–Oulujärvi Subprovince – A linear belt; a rather constant NNW–SSE • Definition: structural trend with local bends having an – A structural subprovince (LT-FIN-SP) char- apparent sinistral sense (late collision stage?). acterized by (1) its structural features and (2) – Cover more upright in the N part (Kainuu Belt) the tectonic setting. compared to the Outokumpu–Rääkkylä Belt – The province is defined by structures related due to less overall tectonic shortening in the to the major collision (ca. 1.91–1.90 Ga) south. along the present R–L Suture and closure – Thin-skinned deformation (e.g., Outokumpu of a narrow proto-oceanic basin along the Allochthon) and basement involving deforma- present Jormua–Outokumpu Suture tion with variable style and intensity. – Tectonic setting of the unit: Re-activated – Both the allochthonous and parautochtho- basement of the Iisalmi–Pudasjärvi Tectonic nous cover schists are tightly folded; the Subprovince within the foreland fold and lowermost quartzites are locally imbricated thrust belt. (with S–C fabric) rather than folded. – Rank (LT-FIN-SP): Subprovince; upper rank – Deformation of the basement is poorly Svecokarelia SP studied – Informal name: Iisalmi block (structural block) – Archean supracrustal domains (e.g., Nun forms the core of the subprovince nanlahti area) show structures correspond- • Description: ing to the cover schists. – An extensively reactivated part of the base- – Basement inliers breaching through the ment within the Iisalmi–Pudasjärvi Tectonic cover and cover outliers within the base- Subprovince; zonal deformation with thrust ment are characteristic. or shear zone-related high-strain zones is – The deformation intensity rapidly fades east- characteristic wards within the basement complex; Archean – The southern-central part (Iisalmi Block) granitoids display an indistinct structural represents deeper levels of the Archean crust grain, even near the contact of the basement exposed due to Paleoproterozoic tectonic pro- and the deformed cover rocks. cesses (both early extensional exhumation and – Spatial irregularities (along the strike) in subsequent thrusting?).

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– The style and prominence of the structural 4.3.1.3 North Ostrobothnia Subprovince overprinting are highly variable. • Definition: – The southern part (Kuopio area) is charac- – A structural subprovince (LT-FIN-SP) char- terized by (semiductile?) basement defor- acterized by (1) its structural features and (2) mation and numerous cover outliers. the tectonic setting. – The eastern margin is thrusted and strongly – The province is defined by structures related sheared; strong (proto)mylonitic foliation to the major collision (ca. 1.91–1.90 Ga) is common; related retrograde metamor- along the present R–L Suture. phism of Archean high-grade rocks and – Tectonic setting of the unit: Foreland fold Paleoproterozoic mafic dykes. and thrust belt on the western side of the – Minor tight outliers of cover rocks within Iisalmi–Pudasjärvi Tectonic Subprovince; basin the basement complex (e.g., Nilsiä area). inversion, crustal shortening and folding – Archean supracrustal rocks in the northern against to the Iisalmi–Pudasjärvi Block. part dominated by Paleoproterozoic over- – Rank (LT-FIN-SP): Subprovince; upper rank printing structures, including penetrative Svecokarelia SP foliation. – Informal name: North Ostrobothnia Fold and – Major Oulujärvi and Hirvaskoski Shear Thrust Belt Zones (reactivated collision-related struc- • Description: tures?) dominate the northern part of the – Linear belt; a rather constant NW–SE struc- subprovince. tural trend with minor local variations. – Paleoproterozoic metamorphic overprinting – NE-vergent, dominantly thin-skinned thrusts; low to medium grade (Archean metamorphic a NW–SE foliation trend is typical; grade variable from medium to high grade – First pervasive foliation of the cover rocks (granulite facies); for details see Mänttäri & – A–P nonconformity formed the major thrust Hölttä 2002, Hölttä & Heilimo 2017). detachment • Nature of unit boundaries: – The intensity and style of basement involve- – Eastern boundary: J–O Suture; see Table 6 ment differs between SE and NW parts. – Western boundary (with North Ostrobothnia – In SE parts, thrust slicing with basement Subprovince) inliers and cover outliers is characteristic – Nature: Lithogenetic contact>Deformation and the Archean supracrustal domains show boundary zone (Structural) structures corresponding to cover schists. – Spatial features: – In NW parts, the structural overprinting of – Location: Defined the Pudasjärvi basement block is limited to – Nature: Gradational (with thrust slices the proximity of the mapped basement– and increasing ductility towards the cover cover boundary. rocks within the North Ostrobothnia – Cover rocks display middle amphibolite facies Subprovince) metamorphism all along the Province. – Width: Wide zone • Nature of unit boundaries: – Northwestern boundary: – Eastern boundary (in the SE part): see west- – Nature: Faulted contact>Fault zone> ern boundary of the Kuopio–Iisalmi–Oulujärvi Transcurrent fault (Structural) (Oulujärvi Subprovince Shear Zone; Hirvaskoski Shear Zone) – Northeastern boundary (in the NW part): – Spatial features: – Nature: Lithogenetic contact>Deformation – Location: Defined boundary zone (Structural) – Nature: Gradational – Spatial features: – Width: Narrow zone – Location: Defined (with rapidly decreas- • Key references: Paavola 1984, Park et al. 1984, ing intensity of structural overprinting Kohonen et al. 1989, 1991, Kärki et al. 1993, within the basement) Hölttä & Paavola 2000, Halla 2002, Mänttäri & – Nature: Gradational Hölttä 2002, Sorjonen-Ward & Luukkonen 2005, – Width: n/a Kontinen & Paavola 2006, Korja et al. 2006. – Southwestern boundary: R–L Suture; see Table 6

67 Geological Survey of Finland, Bulletin 412 Jarmo Kohonen, Raimo Lahtinen, Jouni Luukas and Mikko Nironen

• Key references: Korkiakoski 2002, Lahtinen et al. printing by later folding (see Kola–Lapland 2015b, Laine et al. 2015 Structural Province). – The presented (preliminary) province bound- 4.3.2 Norbotten–Lapland Structural Province aries (and possible subdivision) will develop with further research. • Definition: – Abundant (post-thrusting age) intrusives – A structural province (LT-FIN-SP) character- within the Central Lapland Granitoid Complex, ized by (1) its structural features and (2) the together with younger deformation related tectonic setting. to the Venejoki thrust zone, complicate the – The province is defined by structures related regional structural outline. to the collision along the present K–M–T – Cover rocks mostly display middle amphibolite Suture ca. 1.91–1.90 Ga ago. facies metamorphism, but the southernmost – Overprinting structures within the Karelia parts (Kuusamo and Peräpohja belts) and parts Tectonic Province of Central Lapland indicate greenschist facies – Folding and development of pervasive conditions (Hölttä & Heilimo 2017). to indistinct foliation within the cover Nature of unit boundaries: sequence • Western boundary: K–M–T Suture; see Table 6 – Overall basement (semiductile?) involve- – ment in deformation is minor – Southern boundary: – Tectonic setting of the unit: Foreland fold – Nature: Faulted contact>Fault zone (Struc and thrust belt (peripheral) tural) (Basin margin normal fault reacti- – Rank (LT-FIN-SP): Province; no upper rank vated as a thrust zone in Peräpohja (Skyttä • Description: et al. 2019) and plausibly also in Kuusamo) – A wide structural belt with an indistinct over- – Spatial features: all N–S structural trend; spatially comprises – Location: Well defined major parts of Central Lapland, Peräpohja and – Nature: Gradational to sharp Kuusamo belts with parts of the basement in – Width: Narrow zone the Eastern Lapland Area further to the east. – Eastern boundary: – Substantial crustal shortening in the west- – Nature: Lithogenetic contact>Deformation ernmost parts; very minor shortening in the boundary zone (Structural) easternmost parts – Spatial features: – The overall structural style, foliation trend and – Location: Defined (with rapidly decreas- intensity vary in different parts ing intensity of structural overprinting – Steep thrust stacking of the quartzite-dom- within the basement) inated cover rocks and east vergent, thin- – Nature: Gradational skinned thrusts (e.g., Central Lapland nappe – Width: n/a complex; Luukas et al. 2017) are typical in – Boundary with the Central Lapland granitoid the western part. area: – The deformation intensity wanes towards – Nature: Lithogenetic contact>Deformation the E; in eastern parts, the intensity of the boundary zone (Structural) or Igneous deformation is highly variable and intense intrusive contact (Intrusive); variable in deformation only exists along reactivated different places basement fault zones – Spatial features: – Subhorizontal cover-involving thrusts – Location: Poorly defined are present, but both their abundance – Nature: Undefined and tectonic linkage are still disputable. – Width: n/a – The eastern Lapland basement area (east – Northern Boundary: see southern boundary of Savukoski) displays very minor struc- of the Inari Subprovince (of the Kola–Lapland tural overprinting and is mainly excluded Structural Province) from the Subprovince. • Key references: Hölttä et al. 2007, Nironen – Towards the N, marked interference with 2017b, Piippo et al. 2019, Lahtinen et al. 2015c, features linkable to the Kola–Karelia colli- Silvennoinen 1972, Skyttä et al. 2019, Luukas et sion; in the northernmost parts, clear over- al. 2017, Lahtinen et al. 2018

68 Geological Survey of Finland, Bulletin 412 Classification of regional-scale tectonic map units in Finland

4.3.3 Muonio–Ropi Structural Province morphic grade decreases with lessening deformation towards the west (Hölttä & Heilimo • Definition: 2017). – A structural province (LT-FIN-SP) character- • Nature of unit boundaries: ized by (1) its structural features and (2) the – Eastern boundary: K–M–T Suture; see Table 6 tectonic setting. – Western boundary: – The province is defined by structures related – Nature: Lithogenetic contact>Deformation to the collision along the present K–M–T boundary zone (Structural) Suture ca. 1.91–1.90 Ga ago. – Spatial features: – Overprinting structures within the Norr – Location: Poorly defined (with decreas- botten Tectonic Province (western side of the ing intensity of structural overprinting K–M–TS) within the basement) – Folding and pervasive foliation within the – Nature: Gradational cover sequence – Width: n/a – Overall basement involvement is evident; • Key references: Nironen 2017b, Kärki et al. 1993, details of the deformation style in differ- Bergman & Weihed 2020. NOTE: due to sparse ent parts of the SP are poorly known references, the analysis of map information (e.g., – Tectonic setting of the unit: Retroarc fore- Nironen et al. 2016, Bedrock of Finland - DigiKP) land fold and thrust belt (upper plate setting) was used as one major source for the description. – Part of a larger (unnamed) structural province in Sweden, Finland and Norway 4.3.4 Hetta–Jergul Structural Province – Rank (LT-FIN-SP): Province; no upper rank • Definition: • Description: – A structural province (LT-FIN-SP) character- – Overall N–S structural trend following the ori- ized by (1) its structural features and (2) the entation of the adjacent suture; the province tectonic setting. spatially covers most of the Finnish Norrbotten – The province is defined by structures related Tectonic Province. to the collisions along the present K–M–T – Eastern areas, adjacent to the K–M–TS, show Suture (W side) and along the V-I Suture (far rather ductile younger (post-collision stage) in the NE) ca. 1.91-1.90 Ga ago. deformation involving the basement, the cover – Tectonic setting of the unit: Tectonic set- and the Paleoproterozoic felsic plutons; ting undefined; currently basement block – Deformation along the Pajala Shear Zone between K–M–TS and west-vergent thrusts (Kärki et al. 1993; Pajala Deformation Belt, related to the Kola–Karelia collision; a rifting Bergman & Weihed 2020) caused major stage origin (?) as a basement horst between transposition of the earlier collision-related volcanic–sedimentary depositories (present structures. Kautokeino and Karasjoki belts). – The east-vergent thrust structures are over- – Southern part of a larger structural province printed by lateral displacement (Nironen in Finland and Norway 2017b). – Rank (LT-FIN-SP): Province; no upper rank – The dome-and-basin style pattern of the – Informal name: Hetta–Jergul (structural) block basement and cover is typical for the NW part • Description: of the province. – East-vergent basement involving thrusts (e.g., – Both the intensity of the deformation and the eastern contact of the Hetta–Jergul block; structural overprinting in the Archean base- see Nironen et al. 2016) and the related trans- ment gradually decrease towards the W. position of structures are characteristic in the – Foliation mostly weakly developed in base- western and central parts. ment granitoids – Overriding west-vergent thrusts are charac- – Westernmost cover outliers and fading teristic for the eastern margin overprinting fabric mark the western mar- – Major shear and deformation at the margins gin of the province (next to the basement–cover interface); some – Cover rocks display high amphibolite facies of the basement rocks show minor structural metamorphism in the eastern part; the meta- overprinting (?).

69 Geological Survey of Finland, Bulletin 412 Jarmo Kohonen, Raimo Lahtinen, Jouni Luukas and Mikko Nironen

– The area is poorly exposed and detailed struc- retroarc basin (Inari Subprovince or Lapland tural knowledge is limited. Granulite Belt); main foliation in granulites. • Nature of unit boundaries: – Foreland deformation and folding of the – Eastern and western boundary: cover sequence further south (Sodankylä – Nature: Faulted contact>Fault zone (Struc Subprovince). tural) (Thrust fault zone separating the – Paleoproterozoic metamorphic pattern within basement and cover) the province is heterogeneous – Spatial features: – Northern parts show high amphibolite and – Location: Well defined granulite facies assemblages – Nature: Gradational to sharp – The Sodankylä Subprovince indicates mid- – Width: Narrow zone dle amphibolite to greenschist facies meta- • Key references: Henderson et al. 2015, Bingen et morphism of cover rocks (Hölttä & Heilimo al. 2015, Nironen et al. 2016 2017). • Nature of unit boundaries: see Subprovinces 4.3.5 Kola–Lapland Structural Province • Key references: Gaál et al. 1989, Patison et al. 2006, Nironen 2017b, Lahtinen & Huhma 2019 • Definition: – A structural province (LT-FIN-SP) character- 4.3.5.1 Kaldoaivi Subprovince ized by (1) its structural features and (2) the • Definition: tectonic setting. – A structural subprovince (LT-FIN-SP) char- – The province is defined by structures related acterized by (1) its structural features and (2) to the collision along the present Pechenga– the tectonic setting. Imandra–Varzuga Suture ca. 1.91 Ga ago. – The subprovince is defined as the area – Overprinting structures within the Karelia between the Pechenga–Imandra–Varzuga Tectonic Province (southern side of the P–I–VS) Suture in the NE and the structurally distinct – Variable deformation style reflected in the Inari Subprovince in the SW; the structural division into three subprovinces characterization of the subprovince is cur- – Tectonic setting of the unit: Retroarc rently not sufficient. foreland fold and thrust belt (upper plate – Tectonic setting of the unit: The detailed setting) tectonic set-up of the basement body with – The detailed tectonic setting is compli- Paleoproterozoic subduction-related intru- cated to resolve; several alternatives have sive rocks (ca. 1.98–1.91 Ga) is not fully been proposed (see Kola Province). resolved; deformed continental arc (?) – Rank (LT-FIN-SP): Province; no upper rank – Rank (LT-FIN-SP): Subprovince; upper rank • Description: Kola–Lapland Structural Province – The description is hampered by difficulty in • Description: the separation of the collision-related struc- – The structural style within the subprovince is tures from structures related to a later short- highly variable and detailed structural studies ening event are lacking. – Some of the present structures, such as – A wide belt displaying a very indistinct renewed shortening (ca. 1.88 Ga) and pro- overall NNW–SSE structural trend with posed orocline buckling (between 1.87 and oval-shaped, dome-and-basin resembling 1.80 Ga), represent Svecofennian tectonic map patterns development later (see Lahtinen & Huhma – The structural style and amount structural 2019 and references therein) than the col- overprinting in Archean rocks are poorly lision-related deformation considered here. known. – Major features as a response to the collision: – High-grade metamorphism is characteristic – Deformation of the Archean basement and for the entire subprovince subduction-related intrusives (see Crustal – The original character of the southern bound- Provinces: Northern Lapland Subprovince) ary is obscured by later deformation (see represented by the Kaldoaivi Subprovince Patison et al. 2006) – Intense thrusting within the shortened

70 Geological Survey of Finland, Bulletin 412 Classification of regional-scale tectonic map units in Finland

• Nature of unit boundaries: – Nature: Gradational to sharp – Northern boundary: Pechenga–Imandra–Var – Width: Narrow zone zuga Suture; see Table 6 • Key references: Tuisku et al. 2006, Patison et – Southern boundary: al. 2006, Nironen 2017a,b, Luukas et al. 2017, – Nature: Faulted contact>Fault zone Lahtinen & Huhma 2019 (Structural) – Spatial features: 4.3.5.3 Sodankylä Subprovince – Location: Defined • Definition: – Nature: Undefined – A structural subprovince (LT-FIN-SP) char- – Width: Narrow zone acterized by (1) its structural features and (2) • Key references: Patison et al. 2006, Nironen the tectonic setting. 2017b, Lahtinen & Huhma 2019; due to sparse – The subprovince is defined as the area references, the analysis of map information south of the Northern Lapland nappe sys- (e.g., Nironen et al. 2016, Bedrock of Finland - tem sole thrust and where the structural DigiKP) was used as a major source for the fabric-related Kola–Lapland collision is description. recognized. – Tectonic setting of the unit: Reactivated cra- 4.3.5.2 Inari Subprovince tonic (retroarc) foreland showing domains • Definition: of minor crustal shortening and a separate – A structural subprovince (LT-FIN-SP) char- allochthonous unit (Sodankylä nappe; Luukas acterized by (1) its structural features and (2) et al. 2017) with intense south-vergent struc- the tectonic setting. tures (Evins & Laajoki 2002) – The subprovince is defined as the area cor- – Rank (LT-FIN-SP): Subprovince; upper rank responding to the Lapland granulite belt; Kola–Lapland Structural Province both spatially and structurally, the subprov- • Description: ince is distinctly defined. – A wide belt with an overall NW–SE structural – Tectonic setting of the unit: Upper plate trend; variable deformation styles; detailed deformation of a retroarc basin. structural studies are few (Evins & Laajoki – Rank (LT-FIN-SP): Subprovince; upper rank 2002, Nironen & Mänttäri 2003) Kola–Lapland Structural Province – The subprovince overlaps spatially with the – Informal name: Lapland granulite belt Norrbotten–Lapland Structural Province • Description: – Overprinting/interference structures par- – A wide belt with an unmistakable NW–SE allel to the roof thrust (N boundary of the structural trend (with slight later bending subprovince) causing the arc shape of the subprovince). – Prominent foliation in the proximity of the – Pervasive, very prominent foliation together roof thrust with granulite facies metamorphism (e.g., – Rapidly decreasing overprinting intensity Tuisku et al. 2006, Hölttä & Heilimo 2017) con- towards the SW (Nironen & Mänttäri 2003); stitute the unique structural characteristics. the extent of structural overprinting towards – Division into basement and cover deforma- the SW is controversial (see Nironen 2017b); tion is not feasible (within a deformed retro- identification of the structures specifically arc basin). connected to the Kola–Karelia collision is • Nature of unit boundaries: not finally resolved. – Northern boundary: see above; the southern – Within the eastern Archean basement, the boundary of the Kaldoaivi Subprovince overprint is minor or absent – Southern boundary: – The metamorphic grade varies from high – Nature: Faulted contact>Fault zone>Thrust (northernmost part) and middle amphibolite fault (Structural) (sole thrust of the North facies (main part) to greenschist facies of the ern Lapland nappe system; ‘Granulite belt southernmost parts (Hölttä & Heilimo 2017). sole thrust’) The detailed relationships of the metamorphic – Spatial features: pattern and the structural evolution are not – Location: Well defined resolved.

71 Geological Survey of Finland, Bulletin 412 Jarmo Kohonen, Raimo Lahtinen, Jouni Luukas and Mikko Nironen

• Nature of unit boundaries: – The system above the Caledonian detach- – Northern boundary: see above; the southern ment (Nalganas sole thrust) consists of boundary of the Inari Subprovince strongly foliated to mylonitic metasedi- – Southern boundary: mentary rocks, amphibolites, gneisses and – Nature: Lithogenetic contact>Deformation igneous rocks. boundary zone (Structural) – Below the Nalganas sole thrust, character- – Spatial features: istic features include some imbrication and – Location: Poorly defined (with decreas- weak deformation of the cover ing intensity of structural overprinting – The boundary of parautochthonous (Jerta within the cover rocks) Nappe) with autochthonous cover is not – Nature: Gradational distinct, but a gradational change from – Width: Narrow zone (?) deformed to intact sedimentary rocks (see • Key references: Evins & Laajoki 2002, Nironen & Fig. 3 in Lehtovaara 1995). Mänttäri 2003, Nironen 2017b – Archean basement remained structurally intact. – The eastern margin of the structural province 4.3.6 Kilpisjärvi Structural Province (Paleozoic) is spatially defined either by the (gradational) lower boundary of the Jerta Nappe (Type 1) • Definition: or, when absent, by the major Nalganas sole – A structural province (LT-FIN-SP) character- thrust (Type 2). ized by (1) its structural features and (2) the – Metamorphic grade is variable and reflects the tectonic setting. structural set-up (Hölttä & Heilimo 2017) – The province is defined by structures related – Amphibolite to greenschist facies in alloch- to the Paleozoic Caledonian Orogeny thonous units – Characteristic structures within the Norr – Very low grade (to nearly unmetamor- botten Tectonic Province phosed) within the cover units – Caledonian thrust sheets and overprint- – Archean high amphibolite facies metamor- ing structures within the foreland phism within the basement complex – Tectonic setting of the unit: Foreland fold and • Nature of unit boundaries: thrust belt (peripheral) related to the closure – Southeastern boundary: of the Iapetus Ocean. The final continent– – Nature (Type 1): Lithogenetic contact> continent collision took place (further W) in Deformation boundary zone (Structural) the Scandian phase (also termed the Scandian – Spatial features: Orogeny) ca. 425–400 Ma ago (e.g., Roberts – Location: Defined 2003, Gee et al. 2008). – Nature: Gradational – Rank (LT-FIN-SP): Province; no upper rank – Width: Narrow to wide zone – Part of a larger (unnamed) structural province – Nature (Type 2): Faulted contact>Fault in Sweden, Finland and Norway zone>Thrust fault (Structural) (Caledonian • Description: sole thrust) – Spatially, the province occupies the ultimate – Spatial features: NW nook of Finland; the fabric is parallel to the – Location: Well defined SW–NE trend of Caledonian Nappe Complexes. – Nature: Sharp – The province represents rocks above and just – Width: Narrow zone below the Caledonian frontal ramp. • Key references: Lehtovaara 1989, 1995, Sipilä – The provinces comprises (1) allochthonous 1992, Kohonen & Rämö 2005, Nironen et al. 2016 units (Vaddas, Nabar and Nalganas Nappes) and (2) parautochthonous (Jerta Nappe) to autochthonous (Dividal group) cover.

72 Geological Survey of Finland, Bulletin 412 Classification of regional-scale tectonic map units in Finland

5 GEOLOGICAL REGIONS IN FINLAND

There is a need for named geographically defined high-grade supracrustal rocks are not denoted geological regions (see Nironen et al. 2002, Vaasjoki as belts. et al. 2005), which cover the whole of Finland and • Some names are modified to improve consist- are geologically relevant. The fundamental differ- ency and some new subregions are introduced ence between provinces and regions is that geo- and characterized. logical provinces are concepts including depth or • Some names (e.g., Savo belt) have been changed time dimensions, whereas the geological regions to avoid confusion with other concepts or are always 2D polygons delimiting an area of similar terminologies. geology at the Earth’s surface (see Blake & Kilgour 1998, Raymond et al. 2018). Regions cannot spatially International examples of application of geologi- overlap each other, and each region is represented cal regions include Bain & Draper (1997), Blake & by a single polygon. Kilgour (1998) and Raymond et al. (2018). Bain & Region names are useful for many practical Draper (ibid.) suggest that in definition of geological purposes, such as generalized maps, map draw- regions the well-established boundaries and names ings and regional descriptions. The main problems are retained, and that the region boundaries can be with the regional geological nomenclature have generalised but may also be based on true geological been the abundance and inconsistency of names. divides such as unconformities. We define ageologi - The unsatisfactory status is in Finland a result of cal region is an informal lithotectonic unit corre- the long reseach history with changing geographic sponding to a relatively large geographical area with names, and different postulates in the formation a cohesive geological assemblage (see Bain & Draper of regional geographic nomenclature (Vaasjoki et 1997). Ideally the region is significantly different in al. 2005). A step forward in regional naming was overall geology from the adjoining regions, but the the proposal by Nironen et al. (2002), and their main purpose is to create a practically functional division is mainly followed here. The demand for a division and nomenclature. slight revision arises from the need to harmonize The geographic boundaries between geological nomenclatures and from the undefined status of regions are may be coincident with any geological the geological regions. The proposed changes are: boundaries. The map extent of a geological region • The term ‘complex’ is in formal usage (Lithodemic may be identical to any map unit of the province unit classification; Luukas et al. 2017). To avoid divisions. Geological regions are included to the confusion, ‘complex’ is not anymore used in the lithotectonic system to prevent further duplication region names. and inconsistency of names. The informal lithotec- • Independent of age, the regions dominantly con- tonic map units referred to as geological regions are sisting of supracrustal rocks are termed as ‘belts’; presented in Figure 9. within the Archean province, the paragneisses and

ACKNOWLEDGEMENTS

Oliver Raymond and Pietari Skyttä are thanked for their constructive reviews that helped to improve and consolidate the manuscript. Anneli Lindh provided valuable assistance with the figures.

73 Geological Survey of Finland, Bulletin 412 Jarmo Kohonen, Raimo Lahtinen, Jouni Luukas and Mikko Nironen

Fig. 9. Geological regions in Finland (modified from Nironen et al. 2002). To aid reading, the large areas with Archean rocks are shown in brown and and the areas dominated by the late, cross-cutting rapakivi-granites are shown in purplish red.

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N., Karvinen, A., Kontinen, A., Kontoniemi, O., Kousa, Precambrian Research 324, 303–323. J., Lauri, L. S., Lepistö, K., Luukas, J., Makkonen, H., Slabunov, A. I., Lobach-Zhuchenko, S. B., Bibikova, E. V., Manninen, T., Niiranen, T., Nikander, J., Pietikäinen, Sorjonen-Ward, P., Balagansky, V. V., Volodichev, O. K., Räsänen, J., Sipilä, P., Sorjonen-Ward, P., Tiainen, I., Shchipansky, A. A., Svetov, S. A., Chekulaev, V. P., M., Tontti, M., Törmänen, T. & Västi, K. 2016. Assess- Arestova, N. A. & Stepanov, V. S. 2006. The Archaean ment of undiscovered metal resources in Finland. Ore nucleus of the Baltic/Fennoscandian Shield. In: Gee, Geology Reviews, 86, 896–923. D. G. & Stephenson, R. A. (eds) European Lithosphere Rasilainen, K., Eilu, P., Halkoaho, T., Iljina, M. & Kari Dynamics. Geological Society of London, Memoir 32, nen, T. 2010. Quantitative mineral resource assess- 627–644. ment of undiscovered PGE resources in Finland. Ore Sorjonen-Ward, P. 2006. Geological and structural Geology Reviews 38, 270–287. framework and preliminary interpretation of the Raymond, O. L. 2003. Australian Geological Provinces, FIRE 3 and FIRE 3A reflection seismic profiles, Cen- Regions and Events – A standardised, national ap- tral Finland. In: Kukkonen, I. T. & Lahtinen, R. (eds) proach. Unpublished report, Geoscience Australia. FIRE Finnish Reflection Experiment 2001–2005.

79 Geological Survey of Finland, Bulletin 412 Jarmo Kohonen, Raimo Lahtinen, Jouni Luukas and Mikko Nironen

Geological Survey of Finland, Special Paper 43, 105– Väisänen, M. & Skyttä, P. 2007. Late Svecofennian shear 159. Available at: http://tupa.gtk.fi/julkaisu/special- zones in southwestern Finland. GFF 129, 55–64. paper/sp_043_pages_105_159.pdf Väisänen, M., Eklund, O., Lahaye, Y., O’Brien, H., Frödjö, Sorjonen-Ward, P. & Luukkonen, E. J. 2005. Archean S., Högdahl, K. & Lammi, M. 2012. Intra-orogenic rocks. In: Lehtinen, M., Nurmi, P. A. & Rämö, O. T. Svecofennian magmatiam in SW Finland constrained (eds) Precambrian Geology of Finland – Key to the by LA-MC-ICP-MS zircon dating and geochemistry. Evolution of the Fennoscandian Shield. Developments GFF 00, 1–16. in Precambrian Geology, vol. 14. Amsterdam: Elsevier, van Hunen, J. & Allen, M. B. 2011. Continental collision 19–99. and slab break-off: A comparison of 3-D numerical Strand, K., Köykkä, J. & Kohonen, J. (eds) 2010. Guide- models with observations. Earth Planet. Sci. Lett., 302 lines and procedures for naming Precambrian geolog- (2011), 27–37. Available at: https://doi.org/10.1016/j. ical units in Finland. 2010 Edition Stratigraphic Com- epsl.2010.11.035 mission of Finland: Precambrian Sub-Commission. Vasey, D., Cowgill, E. & Niemi, N. 2019. The geology of Geological Survey of Finland, Guide 55. 41 p. Available cryptic sutures: an example from the Western Greater at: http://tupa.gtk.fi/julkaisu/opas/op_055.pdf Caucasus. GSA Annual Meeting in Phoenix, Arizona, Tuisku, P. & Laajoki, K. 1990. Metamorphic and struc- USA 2019. Abstracts. Available at: https://gsa.confex. tural evolution of the Early Proterozoic Puolankajärvi com/gsa/2019AM/webprogram/Paper336195.html Formation, Finland – II. The pressure-temperature- Väyrynen, H. 1939. On the geology and tectonics of the deformation-composition path. J. Metamorph. Geol. Outokumpu ore field and region. Geological Survey of 8, 375–391. Finland, Bulletin 124. 91 p. Available at: https://tupa. Tuisku, P., Huhma, H. & Whitehouse, M. J. 2012. Geo- gtk.fi/julkaisu/bulletin/bt_124.pdf chronology and geochemistry of the enderbite series Vuollo, H. & Huhma, H. 2005. Paleoproterozoic mafic in the Lapland Granulite Belt: generation, tectonic dikes in NE Finland. In: Lehtinen, M., Nurmi, P. A. & setting, and correlation of the belt. Canadian Journal Rämö, O. T. (eds) Precambrian Geology of Finland – of Earth Sciences 49, 1297–1315. Key to the evolution of the Fennoscandian Shield. De- Tuisku, P., Mikkola, P. & Huhma, H. 2006. Evolution of velopments in Precambrian Geology14, 195–236. migmatitic granulite complexes: implications from Ward, P. 1987. Early Proterozoic deposition and defor- Lapland Granulite Belt, part I: metamorphic petrology. mation at the Karelian cratonmargin in southeastern Bull. Geol. Soc. Finland 78, 71–105. Finland. Precambrian Res. 35, 71–93. Vaasjoki, M. 1981. The lead isotopic composition of some Williams, I. S., Rutland, R. W. R. & Kousa, J. 2008. A re- Finnish galenas. Geological Survey of Finland, Bulle- gional 1.92 Ga tectonothermal episode in Ostroboth- tin 316. 25 p. Available at: http://tupa.gtk.fi/julkaisu/ nia, Finland: implications for models of Svecofennian bulletin/bt_316.pdf accretion. Precambrian Research 165, 15–36. Vaasjoki, M., Korsman, K. & Koistinen, T. 2005. Over- view. In: Lehtinen, M., Nurmi, P. & Rämö, T. (eds) The Precambrian Bedrock of Finland – Key to the Evo- lution of the Fennoscandian Shield. Elsevier Science B.V., 1–18.

80 Developments in map data management and geological unit nomenclature in Finland Edited by Jarmo Kohonen and Timo Tarvainen Geological Survey of Finland, Bulletin 412, 81–114, 2021

MAJOR THRUSTS AND THRUST-BOUNDED GEOLOGICAL UNITS IN FINLAND: A TECTONOSTRATIGRAPHIC APPROACH

Jouni Luukas1*) and Jarmo Kohonen2)

Luukas, J. & Kohonen, J. 2021. Major thrusts and thrust-bounded geological units in Finland: a tectonostratigraphic approach. Geological Survey of Finland, Bulletin 412, 81-114, 11 figures and 7 tables.

This article summarizes the current knowledge and our general ideas concerning thrust tectonics in Finland. The starting point of this exercise was that the output must: (1) clarify and harmonize terminology and nomenclature related to thrust-bounded geological map units in Finland, (2) be connected to the Finstrati (GTK lexicon for geological units), (3) provide a relevant reference regarding the structural theme layers of the GTK map database, and (4) support understanding of the regional stratigraphic relationships presented in geological maps. In addition, the interpretation forms an overall framework for more detailed structural studies and one constraint for further tectonic and crustal-scale modelling.

In Finland, the foreland fold belts and thrust systems within the metamorphosed and complex folded Precambrian bedrock represent deep structural levels, and the exact locations, even for regionally important thrusts, are not easy to trace. The presented summary of thrust systems is based on our interpretation of previous work, the structural analysis of geological and geophysical maps and application of the presented tectonic models.

The result of our tectonostratigraphic approach is the first country-wide compilation of the major thrust-bounded map units in Finland. The presented units support the understanding of the stratigraphic relationships in regional-scale map compilations. The new division of tectonic and structural provinces was utilized as a framework for the thrust systems. All the thrust-bounded units (nappes, allochthons and thrust stacks) have been named, characterized and linked to the corresponding detachment.

Other scientific key points include: (1) the Raahe–Ladoga thrust system separated from the North Karelia–Kainuu thrust system, (2) the cross-section with thrust-bounded units across the Central Lapland belt, and (3) the spatial connection of the thrust blocks and the coeval shear zones in central and southern Finland. We also briefly discuss the links of the major thrusts and the overall geological evolution of Finland.

Structural and tectonostratigraphic map unit divisions provide a useful toolbox complementing lithology-based classifications. Modern theme-layer-based map databases enable the efficient combination of different interpretations and approaches. The presented results are part of the long-term effort with the country-wide map themes and related non-spatial databases.

Keywords: thrust, thrust system, allochthon, geological unit, geological map, Precambrian, Finland

81 Geological Survey of Finland, Bulletin 412 Jouni Luukas and Jarmo Kohonen

1) Geological Survey of Finland, P.O. Box 1237, FI-70211 Kuopio, Finland 2) Geological Survey of Finland, P.O. Box 96, FI-02151 Espoo, Finland

* Corresponding author, e-mail: [email protected]

https://doi.org/10.30440/bt412.3

Editorial handling by Timo Tarvainen. Received 9.10.2020; Received in revised form 1.2.2021; Accepted 17.2.2021

82 Geological Survey of Finland, Bulletin 412 Major thrusts and thrust-bounded geological units in Finland: a tectonostratigraphic approach

CONTENTS

1 INTRODUCTION...... 84

2 THRUST BELTS, THRUSTS AND TECTONOSTRATIGRAPHY...... 85 2.1 Thrust belts, thrust systems and thrusts...... 85 2.2 Tectonostratigraphic approach...... 86 2.2.1 Allochthonous units...... 86 2.2.2 Other thrust-bounded units...... 86 2.2.3 Map unit definition...... 87

3 REGIONAL DESCRIPTIONS AND DIVISIONS...... 88 3.1 Karelia tectonic province...... 88 3.1.1 Svecokarelia structural province ...... 88 3.1.1.1 North Karelia–Kainuu subprovince...... 90 3.1.1.2 Kuopio–Iisalmi–Oulujärvi subprovince...... 94 3.1.1.3 North Ostrobothnia subprovince...... 95 3.1.2 Norrbotten–Lapland structural province ...... 95 3.1.3 Kola-Lapland structural province ...... 96 3.2 Central Finland tectonic province...... 100 3.3 Southwestern Finland tectonic province...... 101 3.4 Kilpisjärvi structural province...... 101

4 TIME CONSTRAINTS OF THRUSTING ...... 102 4.1 General...... 102 4.2 Main collision stage within the Karelia tectonic province ca. 1.93–1.90 Ga...... 104 4.3 Evidence for thrusting between 1.89–1.86 Ga...... 104 4.4 Proterozoic thrusts and deformation younger than 1.86 Ga...... 105 4.5 Paleozoic thrusting related to the Caledonian orogeny...... 105

5 CONCLUDING REMARKS AND SUMMARY...... 106 5.1 Nature of Paleoproterozoic thrust belts in Finland...... 106 5.2 Comments on the selected approach...... 107 5.3 Summary...... 109

ACKNOWLEDGEMENTS...... 109

REFERENCES ...... 109

83 Geological Survey of Finland, Bulletin 412 Jouni Luukas and Jarmo Kohonen

1 INTRODUCTION

Knowledge of the location and nature of the major map units calls for defined terminologies and thrust zones is essential in understanding the over- procedures similar to the classic stratigraphic all set-up and pattern of the observed lithological approach. We build on the ideas that were devel- map units. In regional geology, new interpretations oped during the compilation of the Geological Map always build on previous research and on the pre- of Finland (Nironen 2017) and in relation to the sented evolution models. Due to the intimate cou- development of the stratigraphic database of GTK pling of tectonic models and interpretation of the (Luukas et al. 2017). Most of the defined map units observed features (faults, lithological successions), are based on previous interpretations or derived deeper understanding of regional geology requires from existing descriptions, and in the harmoniza- structural concepts and terminology that provide a tion process, some generalization and simplification context for the actual map units. of the original interpretations could not be avoided. Our starting point was the remark that the appli- The underpinning structural ideas of the authors cation of tectonic concepts (such as collision-related have influenced the process, and both the overall nappe tectonics) has substantially improved under- ambience of the article and the concrete result, the standing of the geology of Finland. The increasing thrust-bounded map units, are ultimately governed availability of geophysical data and their interpreta- by our interpretations. tions (e.g. Kukkonen & Lahtinen 2006) have indi- Thrust-bounded map units (like allochthons) cated that even the major, crustal-scale shear zones and their bounding surfaces, thrusts, are intimately were in the past either neglected or not recognized. linked. Therefore, a summary of the current knowl- The research themes have varied in the course of edge concerning thrust tectonics and major thrust time and between different regions. Therefore, the systems in Finland is presented. Other faults and understanding of thrust tectonics and the recogni- fault systems, such as normal faults, are outside the tion of thrust-bounded map units have not been current scope. The shear zones and their kinematics uniform in all parts of the country. The improved are discussed only in relation to thrust-bounded general knowledge of shear zones and awareness map units and their structural context. of their existence has interacted both with the tec- The main objectives of the article are: (1) to tonic models (e.g. Lahtinen et al. 2005, Nironen outline the thrust systems and thrust-bounded 2017) and country-wide bedrock map compilations units, which are essential in understanding the (e.g. Korsman et al. 1997, Nironen et al. 2016). In stratigraphic relationships displayed in regional- some cases, the meaningful division of map units scale geological maps, (2) to explain observed and requires an indication of their assumed allochtho- inferred thrusts in terms of their genesis and rela- nous nature. A classic example is the Outokumpu tionship with the geological evolution of Finland allochthon in eastern Finland (e.g. Wegmann 1928, and (3) to provide interpretation complementing Koistinen 1981). Another case history is the intro- the country-wide structural map theme and the duction of the Kittilä allochthon concept (Hanski related Finstruct database. Our work is part of a 1997), which opened some stratigraphic deadlocks larger development effort: the construction of the in central Lapland. new GTK Map Data Architecture with a structured Our primary aim is to define and describe the system of spatial data (map themes) and related thrust-bounded geological units relevant for non-spatial databases (e.g. Finstrati, Finstruct; understanding the overall regional set-up pre- see Ahtonen et al. 2021; this volume). Therefore, sented in maps and models. Basically, the approach improved terminological consistency and charac- is pragmatic and conceptually similar to tecton- terization of the geological units are of primary ostratigraphy (e.g. NCS 1989): in orogenic belts importance. The ultimate goal is to compose a (or their parts), where thrusts are the dominant layered system of map themes, which would be and most mappable features, systematic geological capable of storing geological information in all its description is not possible without thrust-bounded complexity and provide a versatile source for 3D map units and related nomenclature. modelling and various other use cases. The attempted systematic description and characterization of the regional-scale thrust-bounded

84 Geological Survey of Finland, Bulletin 412 Major thrusts and thrust-bounded geological units in Finland: a tectonostratigraphic approach

2 THRUST BELTS, THRUSTS AND TECTONOSTRATIGRAPHY

In the literature, the terminology related to thrust Geology (Neuendorf et al. 2005) and IUGS-CGI systems is not unambiguously defined or, at least, GeoSciML (https://cgi-iugs.org/project/geosciml/) the usage of the terms is not fully consistent and vocabularies. For a more comprehensive termino- individual usages vary widely. Therefore, we first logical discussion, the reviews by McClay (1992) and provide some background and clarify the key terms Poblet & Lisle (2011) are referred to. used. The main references are the AGI Glossary of

2.1 Thrust belts, thrust systems and thrusts

A thrust belt (or fold-and-thrust belt; FTB) is a and genetic similarities. Geologically, thrust sys- deformed belt in which contractional or transpres- tems manifest zones of significant crustal thick- sional brittle and brittle-ductile structural styles ening as a response to contractional tectonism. dominate over other types of structures. FTBs most According to the Glossary of Geology, thrust (and commonly evolve out of either passive margin or thrusting) refers to ‘an overriding movement of one intracratonic rift systems, where the extensionally crustal unit over another, as in thrust faulting’. Thrust thinned continental crust has accommodated depo- is used here as a structural concept and a general sitional basins. In collision, the weakness of the term corresponding to the end result of thrusting extended crust concentrates tectonic shortening, (fault, fault zone, shear zone), which may also be which focuses compressional stress, and the basi- interpreted or inferred. Detachment is any major nal rocks subsequently become incorporated into break (fault or shear zone) in the structural conti- the thrust belt. Reactivated extensional faults and nuity of a system; the unit above a thrust detach- uplifted basement blocks are typical ‘basin inver- ment may show structures (such as folding) that sion’ features of deeply exhumed FTBs. are different from the underlying unit. Fold-and-thrust belts are generally divided into In description, the distinction between shallow domains of autochthonous (or parautochthonous) thrust faults and steeper reverse faults may be use- characteristics and domains interpreted as tec- ful. Nonetheless, early thrust structures are often tonically emplaced or allochthonous. The regional deformed, potentially steepened in a subsequent deformation style involving the cover rocks above contractional process, and the original dip of a shear a decollement is known as thin-skinned tectonics. plane is often not possible to assess. In addition to In thick-skinned foreland systems, the underlying thrust faults, the thrusting may occur as fold-thrust basement is also involved in the thrust system and uplifts and in many cases result in asymmetric deformation. Close to the basement–cover interface, folds with highly thinned or thrusted lower limbs. imbricate fans and duplex structures are charac- Generally, thrusts cause an older-over-younger teristic and, consequently, the distinction between relationship and a structural break in the normal the genuine autochthon and deep-level duplex or stratigraphic superposition, but younger-over- imbricate systems is not always possible. older thrusts by re-activation of early extensional Most of the best-studied FTBs (e.g. the Alps, the normal faults are common at basin margins. Canadian Rocky Mountains) are relatively high- Sole thrust (basal thrust, floor thrust) refers to level foreland fold-and-thrust belts when compared the lowest thrust and the frontal thrust marks the to upper greenschist facies to granulite facies (cf. leading edge of the thrust system (Fig. 1); it may Hölttä & Heilimo 2017) FTB examples in Finland. be the major sole thrust, but also a less promi- Accordingly, instead of ramp-and-flat geometries, nent thrust within the frontal unit of the system. features such as ductile fold nappes, imbrication According to the CGI vocabulary, decollement is fans, duplexes and basement involving thrust a large displacement (kilometres or tens of kilo- ramps are typical. metres) along a shallowly dipping to subhorizon- In the Glossary of thrust tectonics terms (McClay tal fault or shear zone. Typically, a decollement 1992), a thrust system is defined as a zone of closely is nearly bedding parallel and occurs along the related thrusts that are geometrically, kinematically basement–cover interface or a mechanically weak and mechanically linked. We use the term for wide rock unit. Rock units above a thrust decollement zones where the thrusts show kinematic, geometric are allochthonous.

85 Geological Survey of Finland, Bulletin 412 Jouni Luukas and Jarmo Kohonen

2.2 Tectonostratigraphic approach

Tectonostratigraphy is not an internationally 1989). Tectonostratigraphic units are applied when formalized stratigraphic category, and it is not the thrust system is well established with published included in the International Stratigraphic Guide information, and where the major thrusts form the (Salvador 1994) or North American Stratigraphic one primary basis for the rock unit division (e.g. Nomenclature (NACSN 2005). In the Scandinavian Caledonides). research tradition, tectonostratigraphic classifi- The term nappe is reserved for tectonostrati- cation is widely used, and denoted in the national graphic classification, and all other inferred alloch- stratigraphic guides (Norway: NCS 1989; Finland: thonous units are here simply called allochthons. Strand et al. 2010; Sweden: Kumpulainen 2017). In our text, the assumed allochthonous nature of a Without caution and care, the different classifi- unit is indicated by the term ‘allochthon’, ‘nappe’ or cation categories and their parallel use may lead ‘nappe complex’ as a part of the unit name. Thrust to complexity and confusion. Our approach and sheet is the lower rank of a nappe, but we use the application of thrust-bounded units is very close term primarily for any mappable volume of rock to tectonostratigraphy and follows the definition by bound below by a thrust. Klippe is an outlier (ero- NCS (1989): Tectonostratigraphy is concerned with the sional remnant) of an allochthon (or nappe) and stratigraphic division of bodies of rock which are piled on window is an inlier surrounded by an overlying top of each other and separated by thrusts. decollement at the present erosional level. Nevertheless, we do not entirely follow the map unit division and terminology of NCS (1989). We 2.2.2 Other thrust-bounded units apply the general term thrust-bounded unit to a body of rock that has been displaced along a thrust Not all thrusts are low-angle detachment zones, (sole thrust) and may be delimited uppermost and the steeper fault zones may also delineate map by a roof thrust or the erosion surface. A tecton- units useful in regional description. We use the term ostratigraphic unit is used for a thrust-bounded thrust stack for imbricated or duplexed thrust sheet unit with a formal tectonostratigraphic status. All systems when the decollement is not identified or thrust-bounded units may consist of one or more the sole thrust is not a low-angle detachment; a lithostratigraphic or lithodemic units. typical example is a basement-involved foreland thrust system. Thrust block is a special type of a 2.2.1 Allochthonous units thrust sheet, a relatively rigid, voluminous thrust- bounded body of rock. These are especially useful Allochthon is a thrust-bounded unit underlain by in the description of large-scale crustal features. a decollement with an inferred substantial amount Finally, it is emphasized that both conceptually and of tectonic transport (several kilometres, at least). in practice, the allochthon-thrust stack boundaries The formal tectonostratigraphy incorporates a hier- and borders between a thrust stack and the adja- archy with the following ranks: nappe system (or cent parautochthonous fold belt are arbitrary and nappe complex), nappe and thrust sheet (see NCS dependent on case-by-case interpretation (Fig. 1).

Fig. 1. A simple sketch addressing the concepts of an allochthon, a thrust stack, a thrust sheet and a parautochthonous fold belt (modified after Alvarez-Marron et al. 2006).

86 Geological Survey of Finland, Bulletin 412 Major thrusts and thrust-bounded geological units in Finland: a tectonostratigraphic approach

2.2.3 Map unit definition graphic classification (NCS 1989) is not appropriate in cases where the locations of the inferred thrusts The presented thrust-bounded units, such as are uncertain (e.g. poor exposure; complex later allochthons, support the reading of the general deformation) or the overall structural model of the geological maps by providing an explanation for region is ambiguous and not widely agreed. lithological units showing neither superposition nor All thrust-bounded map units are defined (Fig. a shared depositional history with the underlying 2) by their boundaries (sole thrust / roof thrust). sequences. All the decollements and other thrust Both informal units and formal tectonostratigraphic planes have been subjected to later deformation, units are in use. The informal units can be later and precise outlining of the thrust plane traces is renamed and formalized as tectonostratigraphic not always feasible. Especially challenging are: (1) units. To support the structured format of the areas where a high amount of ductile deformation FinstratiKP, the following attributes are suggested followed the thrusting stage; (2) basement-involved for the characterization: thrusts in regions where no cover has been pre- • Name of unit (mandatory) served and (3) large unexposed areas and regions – Derivation of name (by lower detachment / with widespread younger intrusives. Therefore, the other; reference to the published name) generalized polygons of the thrust-bounded units – Former names of the corresponding unit (if display the approximated spatial extent sufficient present) to bring out the basic idea (see Fig. 3). • Boundaries: It is important to see that reverse faults, thrust – Sole thrust of the unit (name; mandatory) faults and shear zones are geological structures, – Description (e.g. approximate age; spatial and are not automatically linked to any geologi- characteristics) cal unit. The Finnish bedrock is occupied by minor – Roof thrust of the unit (if identified) thrusts and reverse faults, and not all of these are • Description thrust-bounded unit boundaries. The establish- – Unit lithology (lithostratigraphic / lithodemic ment of a thrust-bounded map unit is justified units within the thrust-bounded unit) when it simplifies the geological description and – Other description (e.g. metamorphic features) substantially aids the representation of the regional • Key references geology. Application of the proper tectonostrati-

Defined by: Map units:

Crustal scale tectonic boundaries Tectonic province Tectonic subprovince

Characteristic Structural province structures Structural subprovince Structural domain

Nappe Bounding thrust planes Allochthon Thrust stack/block

Fig. 2. Thrust-bounded units (in red) as a part of the GTK structural map unit system (for provinces, see Fig. 3).

87 Geological Survey of Finland, Bulletin 412 Jouni Luukas and Jarmo Kohonen

3 REGIONAL DESCRIPTIONS AND DIVISIONS

Tectonic and structural provinces (Fig. 3) both pro- The Karelia tectonic province represents the fore- vide a tectonic context for the presented thrust sys- lands of two opposing collision zones corresponding tems and aid their regional description. A comment to the present Raahe–Ladoga, Kautokeino–Muonio– is needed to clarify the distinction between the spa- Tornio sutures, both with top-to-the-east trans- tially overlapping ‘thrust systems’ and ‘structural port, and Pechenga–Imandra–Varzuga suture with provinces’. A thrust system is a zone consisting of a the opposite transport direction. The structural linked network of thrusts bounding the allochthons provinces reflect the current knowledge regarding and thrust stacks, whereas structural provinces are the overprinting Svecofennian structures within the defined by the overall structural characteristics and Karelia tectonic province (Fig. 3A). relationships with sutures (for details, see Kohonen The Central Finland and Southwestern Finland tec- et al. 2021; this volume). Although the province (or tonic provinces have not been divided into structural subprovince) boundary may follow a major thrust provinces. The reasons are the overall tectonic com- bounding the allochthon, the conceptual differ- plexity of the assumed collage of several volcanic ence in the divisions is definite. The underpinning arc complexes (cf. Lahtinen et al. 2005) and the tectonic model forms an essential background, and poorly understood nature of the inferred major col- in description we utilize the nomenclature (shown lision zone (Bothnia–Pirkanmaa suture). below in italics to avoid repetition of the reference) proposed by Kohonen et al. (2021).

3.1 Karelia tectonic province

The description of the Karelia tectonic province is an The fundamental difference between the North evolved version of the preliminary ideas presented Karelia-Kainuu and Raahe-Ladoga thrust systems by Luukas et al. (2017). Within the entire province, is their relationship to the Raahe-Ladoga suture the formation of the major thrusts can be bracketed (see Fig. 3B). We presume that the sole thrust of between 1.91–1.88 Ga. The younger deformation and the Raahe-Ladoga thrust system is leading on the related thrusts in Lapland and central Finland are SW-side of the suture, whereas the North Karelia- discussed in Chapter 4. Kainuu thrust system represents tectonic thickening within the Karelia province (the Archean basement 3.1.1 Svecokarelia structural province and the cover sequence). The Raahe-Ladoga thrust system involves Svecofennian rocks and is therefore The Svecokarelia structural province corresponds to partly described as part of the Central Finland tectonic the ancient peripheral foreland fold-and-thrust province. that resulted from arc-continent collision along To simplify, the North Karelia–Kainuu and Kuopio– the present Raaha–Ladoga suture. The framework of Iisalmi–Oulujärvi subprovinces (Fig. 3) are understood the North Karelia-Kainuu thrust system (see Figs. as a combination of thin-skinned and thick-skinned 3 and 4) takes shape by the decollements within structural styles; the detached allochthons deformed cover sequence, the major thrust along the Jormua- independently of the underlying strata, but for most Outokumpu suture and variable styles of basement of the area, basement-involved thrust stacks with involvement. However, many important structural narrow cover outliers and basement thrust sheets questions have remained open. For example, the (inliers) breaching through the cover are character- northern continuation of thrust system (Fig. 3B) istic. Within the less studied North Ostrobothnia sub- and the structures of the basement-involved system province, allochthons dominate in the SW part and (such as the frontal thrust, depth of the sole thrust) the overall basement reactivation seems to be less. are poorly understood.

88 Geological Survey of Finland, Bulletin 412 Major thrusts and thrust-bounded geological units in Finland: a tectonostratigraphic approach

Kola A B ( Province (

K (

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1. Raahe-Ladoga suture Finnish Caledonides thrust system 2. Jormua-Outokumpu suture Northern Lapland thrust system 3. Kautokeino-Muonio-Tornio suture Western Lapland thrust system 4. Pechenga-Imandra-Varzuga suture Raahe-Ladoga thrust system 5. Bothnia-Pirkanmaa suture North Karelia-Kainuu thrust system

Fig. 3A. Tectonic provinces, suture zones and structural provinces in Finland (modified from Kohonen et al. 2021). A = North Karelia–Kainuu structural subprovince; B = Kuopio–Iisalmi–Oulujärvi structural subprovince; C = North Ostrobothnia structural subprovince; D = Sodankylä structural subprovince; E = Inari structural subprovince; HJ = Hetta–Jergul structural province; MR = Muonio–Ropi structural province; K = Kilpisjärvi structural province. Note the overlap of the structural provinces in Lapland. Fig. 3B. A simplified map of the thrust systems, major thrusts and prominent shear zones. Tectonic province boundaries (major suture zones) are also shown for comparison with 3A.

89 Geological Survey of Finland, Bulletin 412 Jouni Luukas and Jarmo Kohonen

3.1.1.1 North Karelia–Kainuu subprovince subcontinental mantle (Jormua ophiolite; Peltonen Models involving major thrusts and related alloch- 2005 and references therein), represent obducted thons have been applied in eastern Finland ever rocks derived from an ancient (ca. 1.96–1.90 Ga), since the pioneering works by Wegmann (1928) and narrow remnant ocean basin. The Tohmajärvi– Väyrynen (1939) were published. The original ideas Nunnanlahti–YläLuosta and Kainuu thrust stacks have been developed further by several authors both were generated as an imbrication fan or duplex sys- in North Karelia (e.g. Park et al. 1984, Ward 1987, tem near the basement–cover interface. The thrust Kohonen 1995) and in Kainuu (e.g. Laajoki 1991, stacks involve both the Karelian cover rocks and the Kontinen 1992, Luukas et al. 2017). Archean basement complex. Across the subprovince, The subprovince is located on the eastern side of the degree of basement reactivation and ductility the Jormua–Outokumpu suture. Within the thrust varies, and the basement inliers represent both system, the Outokumpu and Iijärvi allochthons, imbricated thrust sheets and cores of semiductile with associated ultramafic fragments of Archean disharmonic folds.

Table. 1. Thrust-bounded units of the North Karelia–Kainuu subprovince.

Unit name Sole thrust Main references Lithostratigraphic / Lithodemic units

North Karelia–Kainuu thrust system

Outokumpu Outokumpu Wegmann 1928, Väyrynen 1939; Viinijärvi and Outokumpu allochthon decollement Koistinen 1981, Korsman et al. 1997 suites

*Tohmajärvi–Nunnanlahti– see Fig. 4 and text This paper Lentua complex YläLuosta thrust stack Höytiäinen suite Tohmajärvi suite

Iijärvi allochthon Iijärvi decollement Korsman et al. 1997, Laajoki 2005, Iijärvi formation Kontinen & Hanski 2015 >Jormua thrust sheet This paper Jormua suite (‘Jormua ophiolite complex’)

Kainuu thrust stack Väyrylä thrust Laajoki 1991, Kontinen 1992 >Väyrylänkylä thrust sheet Luukas et al. 2017 (Väyrylänkylä Lentua complex, >Tupala thrust sheet nappe) East Puolanka group >Vihajärvi thrust sheet Luukas et al. 2017 (Tupala nappe) Somerjärvi group >Tulijoki thrust sheet Luukas et al. 2017 (Vihajärvi nappe) Vihajärvi group >Oikarila thrust sheet Luukas et al. 2017 (Tulijoki nappe) Väyrylä group This paper Central Puolanka group

*Not divided into individual thrust sheets

In North Karelia, the major thrusts (see Fig. 4) west (in the Tuusjärvi–Vehmersalmi district), are divided into two groups: (1) the Outokumpu the sole thrust (Räsälä thrust) plunges down and decollement and the internal detachments of the joins the Jormua–Outokumpu suture zone. The allochthon and (2) various basement-involved Outokumpu allochthon has tentatively been divided thrusts. The Outokumpu decollement is well into parts by detachments separating the ophiolite defined in the north (Outokumpu area), whereas in (serpentinite)-containing parts (e.g. Koistinen 1981, the southeastern part of the Outokumpu–Rääkkylä Kontinen et al. 2006) from the rest of the system. belt, both the location and nature of the sole thrust The geometry and composition of these internal are inferred. In Figure 4, we have mainly followed thrust sheets are poorly known, but a slight dif- the map compilation by Korsman et al. (1997). In ference in the greywacke lithologies across the the Juojärvi district, large windows of basement bounding detachments has been proposed (Aatos and parautochthonous cover are exposed through et al. 2016). the Outokumpu decollement, and further to the

90 Geological Survey of Finland, Bulletin 412

Major thrusts and thrust-bounded geological units in Finland: a tectonostratigraphic approach (

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Inferred thrust reactivated Suonenjoki allochthon Iisalmi thrust block as a subvertical shear zone Rautavaara thrust block North Karelia - Kainuu thrust system Manamansalo thrust block Ijärvi allochthon Kalpio thrust stack Outokumpu allochthon Kuopio thrust stack

Fig. 4. The overall configuration of the major thrusts, thrust systems, thrust blocks and shear zones in central and southern Finland (see also Chapters 3.2 & 3.3): (1) Outokumpu decollement, (2) the inferred sole thrust of the Tohmajärvi–Nunnanlahti–YläLuosta thrust stack, (3) Räsälä thrust, (4) Ruhanperä shear zone, (5) Haukivesi shear zone, (6) Lestijärvi shear zone, (7) Kyyjärvi thrust, (8) Perho thrust, (9) Virrat–Jämsä shear zone, (10) Seinäjoki–Karijoki thrust zone, (11) Leivonmäki–Kankaanpää shear zone, (12) Otava–Kynsikangas shear zone, (13) Sulkava thrust, (14) Hyvinkää–Kisko shear zone; NiS = the Nivala suite. The location of Figure 5 is indicated as a box. The geological background map is simplified from Nironen et al. (2016).

91 Geological Survey of Finland, Bulletin 412 Jouni Luukas and Jarmo Kohonen

Within the Höytiäinen belt, the frontal thrust of One fundamental question regarding the upper the Tohmajärvi–Nunnanlahti–YläLuosta thrust parts of the system is the nature of the proposed stack roughly follows the trend of the basement– Iijärvi decollement. The lower contact of the cover boundary. The basement-involved structure is extensive Iijärvi formation (Kontinen 1986) and interpreted to continue towards the NNW from the Kuikkalampi formation (Kontinen & Hanski 2015) Nunnanlahti district to the southernmost tip of the has been interpreted as a thrust detachment and Kainuu belt, along the major shear zones with char- as a sole of the major Iijärvi allochthon. Direct evi- acteristic textures in basement granitoids (blebbed dence for the decollement is not present, and the gneiss of Väyrynen 1939; protomylonite of Kohonen stratigraphic relationships presented by Kontinen 1995; partly mylonitic intense Proterozoic shearing & Hanski (2015) might as well allow a parautoch- of Paavola 2005). During the continued shortening, thonous setting for the Iijärvi formation. The key the thrust zone first steepened and finally reacti- element of the puzzle is the tectonic interpretation vated as a wrench fault during the late stage of the of the Jormua Ophiolite Complex (Jormua suite; contraction (Kohonen 1995), and both the nature see Kontinen 1987, Peltonen 2005) as part of the and the accurate location of the sole thrust remain system. The alternative ophiolite emplacement unclear. Examples of basement-involved structures models and a description of the Jormua–Outokumpu within the Tohmajärvi–Nunnanlahti–YläLuosta suture can be found in Lahtinen et al. (2015b) and in thrust stack are the Suhmura thrust zone (e.g. Ward Kohonen et al. (2021), respectively. Nonetheless, at 1987, Kohonen et al. 2019), the Nunnanlahti thrust this stage, we stick to the established decollement- zone (e.g. Kohonen 1995 and references therein) based interpretation (e.g. Kontinen & Hanski 2015, and the Juuanvaarat–Polvela district, with several Nironen et al. 2016, Luukas et al. 2017), and thus the stacked thrust sheets and narrow cover outliers Iijärvi allochthon is structurally correlated with the within the basement (see Sorjonen-Ward 2006, steep western parts of the Outokumpu allochthon. Bedrock of Finland – DigiKP). The middle structural levels are represented by Rock units within a foreland fold-and-thrust belt the Kainuu thrust stack, which consists of imbri- may exhibit very complex geometries (e.g. Schmidt cated thrust sheets of various lithologies (Laajoki & Perry 1988), and the Kainuu belt is a perfect exam- 1991, Luukas et al. 2017, Bedrock of Finland – ple. The belt shows an assortment of structures with DigiKP). The Kainuu thrust stack is an attempt to assumed origins from basin stage via basin inver- describe the structural style of a system where the sion to late faulting, and the overall deformation original stratigraphic relationships are overrun by style within the belt is very variable. Due to the lack thrust-bounded units (Laajoki 1991). In addition, of detailed structural works and regional analysis, the metamorphic irregularities, such as anoma- only some general features can be presented. The lous low greenschist facies metamorphism of the schist-dominated upper structural levels apparently Oikarila thrust sheet, are difficult to explain with- show a more ductile deformation style compared to out an assumption of major faults (Kontinen 1992). the underlying imbricate stacks in the middle parts However, the precise location of all the detachments, of the system. Nonetheless, even the quartzites was not possible to resolve. Furthermore, the tran- show structural variety from imbrication to tight, sition from the thrust stack to parautochthonous ductile folding. Near the basement–cover interface, cover of the Hyrynsalmi and Puolanka areas (Fig. 5) fragmented quartzite units in places show pecu- is not sharp but a wide zone where the imbrication liar overturned blocks (Kontinen 1989) and other and basement-involved faults gradually decline. features possibly reflecting forceful (semibrittle?) Therefore, the frontal thrust marks the boundary inversion of the early rift basins. Within Kainuu of intense thrust stacking, not the margin of thrust belt, the overall shortening of the system is more faulting and shortening-related deformation. advanced compared to North Karelia, and steeply dipping or upright structures are typical.

92 (

(

( Geological Survey of Finland, Bulletin 412

Major thrusts and thrust-bounded geological units( in Finland: a tectonostratigraphic approach

((

Raahe-Ladoga thrust system Kiuruvesi allochthon Pyhäsalmi allochthon Lentua North Karelia – Kainuu thrust system Complex Iijärvi allochthon Jormua thrust sheet

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and Kajaani thrust stacks are shown and the major( thrusts are indicated by numbers: (1) Tuusjärvi–Alanen–Jormua (

thrust, (2) Iijärvi decollement, (3) Väyrylä thrust, (4) Sonkajärvi thrust, (5) Aittokylä thrust,( (6) Vieremä decol- ( lement, (7) Kiuruvesi decollement, (8) Pyhäsalmi decollement. HSZ = Hirvaskoski shear zone, AF = Auho fault. ( Note the parautochthonous cover on the Archean( basement; see Figure 4 for location. The geological background

map is simplified from Nironen et al. (2016). (

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( ( Geological Survey of Finland, Bulletin 412 Jouni Luukas and Jarmo Kohonen

3.1.1.2 Kuopio–Iisalmi–Oulujärvi subprovince The Sonkajärvi thrust divides the large basement The Kuopio–Iisalmi–Oulujärvi structural subprov- area (Iisalmi terrain of Sorjonen-Ward & Luukkonen ince represents the western, thrusted flank of the 2005) into the western Iisalmi and eastern Jormua–Outokumpu suture (Fig. 3A), and the major Rautavaara thrust blocks (Figs. 5 and 6). The inter- Tuusjärvi–Alanen–Jormua thrust (Fig. 5) marks the nal deformation zones within the Rautavaara thrust eastern margin of the subprovince. The subprovince block are manifested by the narrow cover quartzite is an example of deep-level structures of the thick- outliers of Nilsiä, Keyritty and Pisa (Paavola 1980, skinned foreland fold-and-thrust belt between the 1984), which all show preservation in the over- western Raahe–Ladoga thrust system and the rather turned limb of a basement-involved east-vergent intact basement block (Lentua complex) in the east fold structure. The Kajaani thrust stack, including (see Figs. 4 and 5). Huge bodies of Archean rocks the Kalpio, Mainua and Korholanmäki thrust sheets, were tectonically pushed towards the east (e.g. Korja forms the northern extension of the Rautavaara et al. 2006), and the sole thrust extends from the thrust block. Tuusniemi district (east of Kuopio) to the central No outliers of cover have been observed within parts of the Kainuu belt (Paltamo district). This the Iisalmi thrust block, and the rocks mainly lack basement-involved thrust forms the roof thrust of any thrust-related fabric. We understand the high- the Kajaani thrust stack. Its northern continuation grade metamorphic domains within the rigid Iisalmi (Aittokylä thrust) represents the basal thrust of the thrust block as mid-crustal bodies uplifted and Manamansalo thrust block and the roof thrust of exhumed plausibly during both the extension (c. the underlying Kainuu thrust stack (Fig. 5). 1.98–1.96 Ga) and subsequent collision (c. 1.90 Ga).

Table. 2. Thrust-bounded units of the Kuopio–Iisalmi–Oulujärvi Subprovince.

Unit name Sole thrust Main references Lithostratigraphic / Lithodemic units North Karelia–Kainuu thrust system

Iisalmi thrust block Sonkajärvi This paper Iisalmi complex thrust Rautavaara thrust block Tuusjärvi– Laajoki 2005 (Kajaani tectonic zone); Rautavaara complex; Nilsiä Alanen– this paper group Jormua thrust Manamansalo thrust Aittokylä thrust This paper Manamansalo complex; block Central Puolanka group

Kajaani thrust stack This paper >Kalpio thrust sheet This paper Kalpio complex >Mainua thrust sheet Luukas et al. 2017 (Mainua nappe); Otanmäki suite Kärenlampi et al. 2019 (Otanmäki– >Korholanmäki Kuluntalahti nappe) Sotkamo group thrust sheet Kontinen 1992

*Kuopio thrust stack Räsälä thrust This paper Kuopio complex; Nilsiä, Neulamäki, Levänen groups; Suonenjoki, Kotalahti suites *Not divided into individual thrust sheets

Thin basement slivers interpreted as thrust metamorphic grade, Säntti et al. (2006) reported sheets and associated basement cored anticlines reaction isograds corresponding to ca. 500 °C in are characteristic of the Kuopio thrust stack. The the central parts of the Outokumpu allochthon and area is severely affected by later transpressional up to 700 °C at the eastern margin of the Kuopio deformation, and towards the southwest, both thrust stack, less than 50 km towards the Raahe– the ductility of the basement and the amount of Ladoga suture in the west. In the eastern part of post-collisional intrusives increase. Regarding the the thrust stack several Archean gneiss inliers

94 Geological Survey of Finland, Bulletin 412 Major thrusts and thrust-bounded geological units in Finland: a tectonostratigraphic approach

(thrust sheets) occur within the supracrustal cover The Kiuruvesi decollement is underlain by the rocks. In the southern part (Kotalahti–Leppävirta Archean basement (the Pudasjärvi, Manamansalo area; S of Kuopio), several basement gneiss slices and Iisalmi complexes) and within the Kiiminki form a complicated system alternating with rocks belt by the autochthonous cover rocks. The large similar with the Svecofennian paragneisses of the Kiuruvesi allochthon represents rocks tectonically Suonenjoki allochthon (see Table 6) in the south- transported from the SW side of the Raahe–Ladoga west. In both areas, the original nature and geom- suture, and the allochthon mainly consists of tur- etry of the thrusts have been obliterated by the later biditic sedimentary rocks together with mafic pil- deformation and intrusions. low-structured volcanics (Laajoki &Luukas 1988, Lahtinen et al 2015b). The allochthonous nature 3.1.1.3 North Ostrobothnia subprovince of these rocks was suggested by Luukas (1991) The subprovince is characterized by the eastern part and Pietikäinen & Vaasjoki (1999), and accord- of the Raahe–Ladoga thrust system extending from ing to our interpretation, these rocks were never Oulu to the Kuopio district in the southeast (Table deposited on Archean crust and are thus not con- 3 and Fig. 4). The most remarkable feature is that sidered as part of the cover sequence (or Karelian basement rocks have never been found as inliers formations of Laajoki 2005). In the northern within the Kiuruvesi allochthon, and we assume part of the subprovince, almost all structures are that the unit represents the uppermost levels of the intruded by voluminous (ca. 1.8 Ga) granites, which entire thrust pile within the Svecokarelia Structural obliterate the allochthon and all thrust-related Province. The tectonic setting of these allochthonous structures. rocks has been discussed by Lahtinen et al. (2015b).

Table. 3. Thrust-bounded units of the North Ostrobothnia subprovince.

Unit name Sole thrust Main references Lithostratigraphic / Lithodemic units Raahe–Ladoga thrust system (eastern part)

Kiuruvesi allochthon Kiuruvesi Luukas (1991), Näläntöjärvi, Lampaanjärvi decollement Pietikäinen & Vaasjoki (1999) suites; part of the Kiiminki group North Karelia–Kainuu thrust system

Vieremä allochthon Vieremä decollement Luukas 1991 Rotimojoki fm >Itämäki klippe Luukas et al. 2017 Itämäki fm

The supracrustal cover rocks comprising the Norrbotten–Lapland structural province corresponds Vieremä allochthon and the adjacent Itämäki klippe to a wide FTB with an indistinct overall N–S struc- rest on the Archean basement of the Iisalmi and tural trend. The structural overprinting extends up Manamasalo complexes, and both are interpreted as to Kuusamo (see Figs. 3 and 6) in the east, whereas tectonically transported units, although an alterna- the thrust system is limited to western Lapland tive explanation of parautochthonous outliers can- (Fig. 6). In central Lapland, the models with sup- not be fully excluded. The lithological relationships posed major thrusting gradually emerged from the and other features at the basement–cover contact Kittilä area (e.g. Kontinen 1981, Hanski 1997, Hanski (Vieremä decollement of this paper) have been & Huhma 2005, Peltonen 2005, Hölttä et al. 2007, described by Korkiakoski & Laajoki (1988). Lahtinen et al. 2018) to the Sodankylä area (Evins & Laajoki 2002) and finally also to the Peräpohja 3.1.2 Norrbotten–Lapland structural province belt (Lahtinen et al. 2015a, Piippo et al. 2019). In the following, we summarize the main features of Substantial crustal shortening and thrusting the Western Lapland thrust system and outline an resulted in collision along the present Kautokeino– overall regional reconstruction of the major thrust- Muonio–Tornio Suture in the west (Fig. 3). The bounded units.

95 Geological Survey of Finland, Bulletin 412 Jouni Luukas and Jarmo Kohonen

First, it is important to see that we consider large thon is modified by younger N–S-trending thrusts areas in Lapland as parautochthonous cover within (see Nironen et al. 2016). the foreland fold-and-thrust belt. The main parts The Rovaniemi allochthon is introduced here of the Peräpohja belt (see Perttunen 1991, Perttunen and interpreted as the southern structural coun- & Hanski 2003, Skyttä et al. 2019), the Kuusamo belt terpart for the Kittilä allochthon. The decollement (Lahtinen & Köykkä 2020 and references therein) is severely obscured by the later granites and the and the Central Lapland belt as a whole (e.g. Hanski & eastern boundary is impossible to trace spatially Huhma 2005) are all folded and also thrusted, espe- (Fig. 6). The inferred Rovaniemi decollement, rep- cially along the ancient basin margins. However, in resented by the Korkiavaara and Venejärvi thrusts, all these areas, the primary stratigraphic relation- is possible to identify in the Korkiavaara district (S ships are possible to resolve, and we do not pres- of Rovaniemi) and in the Sieppijärvi district (S of ently see any value in the introduction of vague Kolari). The lithology of these allochthonous rock thrust-bounded units. units corresponds to that of the Ylitornio allochthon The Kittilä allochthon is well established (Hanski (Lahtinen et al. 2015a, Köykkä et al. 2019). 1997, Peltonen 2005) and linked to the western col- The Ylitornio allochthon, showing a strongly lision (e.g. Lahtinen et al. 2005, 2018). The Nuttio– curvilinear geometry of the sole thrust (Martimo Seurukarkea decollement is poorly exposed and decollement; see Fig. 6), was defined and named difficult to locate exactly. Serpentinite bodies (the (Ylitornio nappe complex) by Lahtinen et al. (2019). ophiolitic Nuttio serpentinite belt of Hanski 1997, Within the Peräpohja belt, the inversion of the early Lehtonen et al. 1998) are typical at the proximity rift basin geometry has largely controlled the con- of the sole thrust, and their ophiolitic nature pro- tractional deformation (Lahtinen et al. 2018, Piippo vides evidence for significant tectonic transport but et al. 2019), and both the allochthons (Ylitornio and the kinematic evolution has not been resolved. The Rovaniemi) and the parautochthonous sequence are overall geometry of the map unit reflects interfer- transposed and show an E–W trend due to later ence between the Norrbotten and Kola collisions deformation (e.g. Lahtinen et al. 2018, Sayab et al. (see Fig. 3), and the western boundary of the alloch- 2019).

Table. 4. Thrust-bounded units of the Norrbotten–Lapland structural province.

Unit name Sole thrust Main references Lithostratigraphic / Lithodemic units Western Lapland thrust system

Kittilä allochthon Nuttio-Seurukarkea Hanski 1997, Peltonen 2005 Kittilä suite decollement Ylitornio allochthon Martimo decollement Lahtinen et al. 2019 Martimo suite, Mellajoki suite Uusivirka suite Rovaniemi Rovaniemi This paper Rovaniemi supersuite allochthon decollement

3.1.3 Kola-Lapland structural province Lapland thrust system, the pattern of the major thrusts, is poorly understood. The thrust system is The Northern Lapland thrust system and the Kola– apparently bivergent (Fig. 6), but detailed thrust Lapland structural province are interpreted to be a kinematics and the impact of the suggested mul- result of intense thrusting within a shortened retro- tiple thrusting phases (Lahtinen & Huhma 2019) arc foreland basin (Lahtinen & Huhma 2019), which are not fully resolved. The Northern Lapland thrust is now represented by the high-grade rocks known system defines the following units: (1) three main as the Lapland granulite belt. Foreland deformation allochthons with the linked klippes, (2) the Lokka and folding of the cover sequence extends further and Näätäselkä thrust stacks immediately below south to Central Lapland (Sodankylä area). the main decollement and (3) the frontal Sodankylä Despite extensive research (e.g. Gaál et al. 1989, thrust stack further to the south (Table 5 and Patison et al. 2006, Tuisku et al. 2006), the Northern Fig. 6).

96 Geological Survey of Finland, Bulletin 412 Major thrusts and thrust-bounded geological units in Finland: a tectonostratigraphic approach

The core element of the Northern Lapland thrust Huhma (2019) suggest that these structures are system is the Lapland granulite belt, which has younger than the emplacements of the alloch- always been defined by structural boundaries. The thons. Therefore, both the location of the original, corresponding thrust-bounded unit is named as the major decollement and the nature of the assumed Inari allochthon, which is floored by the prominent Kaamanen allochthon remain unresolved. Angeli–Tankavaara decollement (Table 5 and Fig. The Vuotso allochthon below the Angeli– 8) against the lower Vuotso allochthon (Figs. 6 and Tankavaara thrust (decollement) mainly consists 7). According to our interpretation, the sole thrust of high-grade gneisses and amphibolites. In our of the allochthonous system at the southern margin interpretation, the lithologically similar Lautaselkä is the Vuotso decollement, and the northern bound- and Kotisijamaa klippes represent dismantled frag- ary of the entire system is the Utsjoki thrust. Both ments above the Vuotso decollement (Fig. 8). The the Utsjoki thrust and the parallel Kaamanen thrust Pokka klippe of plutonic rocks with ages of around (Fig. 6) show southwesterly dips, and the sections 1.92 Ga (Lahtinen & Huhma 2019) is tentatively provided by Patison et al. (2006) and Lahtinen & linked to the Inari allochthon.

Table. 5. Thrust-bounded units of the Kola-Lapland structural province.

Unit name Sole thrust Main references Lithostratigraphic / Lithodemic units Northern Lapland thrust system (Northern Lapland nappe system of Luukas et al. 2017; see also Gaál et al. 1989, Patison et al. 2006, Lahtinen & Huhma 2019)

Kaamanen See text This paper Kaamanen complex allochthon

Inari allochthon Angeli–Tankavaara This paper Lapland granulite >Pokka klippe decollement complex

Vuotso allochthon Vuotso decollement This paper Vuotso complex >Lautaselkä klippe >Kotasijamaa klippe

Lokka thrust stack Kurittukoski thrust This paper Sodankylä group Savukoski group Näätäselkä thrust Lisma thrust This paper Sodankylä group stack Savukoski group

Sodankylä thrust stack Postoaapa thrust Luukas et al. 2017, Nironen 2017 Sodankylä group (Sodankylä nappe) Savukoski group Ellitsa thrust Evins & Laajoki 2002

The poorly exposed and studied Lokka and The Sodankylä thrust stack is a complex pack- Näätäselkä thrust stacks represent in our interpre- age interpreted as resulting from two overlapping tation an imbrication fan or duplex structures below thrust systems. According to our interpretation, the allochthonous part of the Northern Lapland the cover rocks were first tectonically transported thrust system. The Lokka thrust stack consists eastwards (mainly along the basement–cover inter- of rocks correlated with the Kuusamo, Sodankylä face). The easternmost Postoaapa thrust (Fig. 7) still and Savukoski groups thrusted over the Archean displays the original orientation of the Western basement. In the Peurasuvanto district, the older Lapland thrust system, but most of these thrusts (Kuusamo group) rocks are pushed over the younger are transposed to an E–W direction or transected cover sequence along the Kurittukoski thrust (see in thrusting with southern vergence. In our model, Figs. 7 and 8). these thrusts are connected to the Northern Lapland

97 Geological Survey of Finland, Bulletin 412 Jouni Luukas and Jarmo Kohonen thrust system, and major displacement occurred not well known, but it appears that the later thrusts along the Ellitsa thrust (Fig. 8). Luukas et al. (2017) are in places associated with asymmetric folding of and Nironen (2017) proposed an allochthonous the basement–cover interface. The younger, south- nature for part of the cover sequence. In Figure 8, dipping thrusts of the Sodankylä area (e.g. Hölttä et the inferred Sodankylä decollement is represented al. 2007) are linked to the Venejoki thrust zone and by the Ellitsa and Postoaapa thrusts. The degree of discussed in Chapter 4.4.

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Fig. 6. The overall configuration of the major thrusts, thrust-bounded units and shear zones in northern Finland. 1) Utsjoki thrust, 2) Kaamanen thrust, 3) Angeli–Tankavaara decollement, 4) Vuotso decollement, 5) Kurittukoski thrust, 6) Nuttio–Seurukarkea decollement, 7) Postoaapa thrust, 8) Ellitsa thrust, 9) Korkiavaara thrust, 10) Venejärvi thrust, 11) Martimo decollement, 12) Nalganas sole thrust (decollement). KPSZ = Kolari–Pajala shear zone; the extent of Figure 7 is indicated as a box. Note the parautochthonous cover on the Archean basement. The geological background map is simplified from Nironen et al. (2016).

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Fig. 8. Schematic cross-section (not to scale) across the Northern Lapland thrust system. Note the sole thrusts following the basement–cover interface in the north and the upper contact of the autochthonous quartzite in the middle part. Within the Sodankylä thrust stack, the basement-involved thrusts reactivate inherited normal faults or occur at the overturned limb of basement-cored anticlines; for the location, see Figure 7.

3.2 Central Finland tectonic province

Major shear zones, several thrusts (e.g. Nironen et (2) the thrusts have transported Svecofennian rocks al. 2016) and related crustal-scale structures (e.g. of the Kiuruvesi allochthon on their current position Sorjonen-Ward 2006) have been suggested within within the Karelia province (Fig. 4). the Central Finland tectonic province, but until now, no The trend of the inferred decollement flooring thrust-bounded map units have been outlined. The the Pyhäsalmi and Suonenjoki allochthons (Table overall structural evolution of the province is rather 6) follows the Raahe–Ladoga suture zone (Fig. 3B). poorly constrained and, for example, the potential These thrusts are truncated by voluminous intrusive impact of extensional tectonics (e.g. Nikkilä et al. rocks and affected by intense younger shear zones 2015) on the generation of shear zones and on the (see Figs. 3B and 4). The Pyhäsalmi and Suonenjoki present map pattern is difficult to evaluate. allochthons are bounded in the west by the younger It is essential to see that within the Karelia tectonic Ruhanperä and Iisvesi shear zones, respectively. province, all the major thrusts in eastern Finland, Along the boundary, voluminous younger intrusions and most of them in northern Finland, are consider have obliterated all the thrust-related early struc- older (ca. 1900 Ma) than the main crustal growth tures beyond recognition. Nonetheless, the rocks stage (ca. 1890–1870 Ma) and coeval volcanism of of the Nivala suite, west of the Pyhäsalmi alloch- the Svecofennian orogeny. The Raahe-Ladoga thrust thon (Fig. 4), can be correlated with the Suonenjoki system (see Chapter 3.1.1) is tectonically signifi- and Kotalahti suites (the latter accompanied by cant for two reasons: (1) within the Central Finland Ni-bearing intrusions). Thus, it seems possible province, only the Pyhäsalmi and Suonenjoki alloch- that the rock units of the Nivala district could rep- thons consist of rock units older (ca. 1930–1900 resent still another tectonic package thrusted over Ma; Lahtinen 1994, Lahtinen et al. 2015b) than the the Pyhäsalmi allochthon. major collision affecting the eastern foreland and

100 Geological Survey of Finland, Bulletin 412 Major thrusts and thrust-bounded geological units in Finland: a tectonostratigraphic approach

Table. 6. Thrust-bounded units of the Central Finland tectonic province.

Unit name Sole thrust Main references Lithostratigraphic / Lithodemic units Raahe–Ladoga thrust system (western part)

Pyhäsalmi allochthon Pyhäsalmi decollement This paper Pyhäsalmi and Vihanti groups

Suonenjoki and Kotalahti suites Suonenjoki allochthon Suonenjoki decollement This paper

Younger major thrust zones are recognized within with apparent dextral lateral displacement (>20 the Central Finland tectonic province. The combined km), separates the Perho and Kauhajoki blocks. interpretation of seismic sections and field observa- The Perho thrust forms the roof of the Perho block tions indicate the existence of crustal-scale thrust against the Ostrobothnia metasediments, and the blocks, and their provisional boundaries are tenta- floor is defined by the Kyyjärvi thrust (Fig. 4). A tively addressed in Figure 4. The thrust-bounded prominent, SE-plunging lineation is associated crustal domains of this group include: (1) Perho with both faults (Pipping & Vaarma 1993). A simi- thrust block (Sorjonen-Ward 2006), (2) Kauhajoki lar SE-plunging lineation has been found in Parra thrust block and (3) Sulkava thrust block (Korsman within the Seinäjoki–Karijoki thrust (Lehtonen et al. 1988). et al. 2005). All these lineations are interpreted The Perho block was identified in the interpre- to indicate relatively widespread tectonic trans- tation of the FIRE 3 profile (Sorjonen-Ward 2006). port towards the NW (for the age constraints, see In our interpretation, the Virrat–Jämsä shear zone, Chapter 4).

3.3 Southwestern Finland tectonic province

Many authors (e.g. Väisänen & Hölttä 1999, Pajunen all upright position and discontinuity of the early et al. 2008) have assumed low-angle thrusting as structures. Third, southern Finland was still the site an explanation for the early structures within the of intensive granitic magmatism 1.85–1.80 Ga ago, Southwestern Finland tectonic province. However, the and the possible thrust-bounded units are difficult problems related to the recognition of early low- to identify and trace. Nevertheless, there are some angle thrusts are severe. First, the tectonic set- stratigraphic indications of possible thrust stack- up and structural history (e.g. contractional vs. ing. One example is the Hyvinkää–Kisko shear zone late extensional stages; see Lahtinen et al. 2005, (Skyttä et al. 2006, Pajunen et al. 2008), where the Pajunen et al. 2008, Korja et al. 2009) are poorly southern high-grade rocks (Kimito suite) appear understood or at least controversial. Second, the to be thrusted over the rocks of the Häme belt. In intensive ductile folding followed by the develop- Figure 4, we tentatively present a set of inferred ment of the major shear zones resulted in an over- major thrusts in southern Finland.

3.4 Kilpisjärvi structural province

The Kilpisjärvi Structural Province (see Fig. 3) comprise the Nalganas, Nabar and Vaddas Nappes represents the extent of the Caledonian structural (Table 7). Below the Nalganas sole thrust, char- overprint in Finland. The Finnish Caledonides thrust acteristic features include some imbrication and system and the rocks deformed above and imme- weak deformation of the cover. The boundary of diately below the frontal thrust of the Caledonian parautochthonous (‘Jerta Nappe’) and autochtho- thrust belt, have been described by Lehtovaara nous cover (Dividal group) is not distinct but shows (1989, 1995). The major thrusts and the tecton- a gradational change from deformed to intact sedi- ostratigraphic division (Lehtovaara 1995) are largely mentary rocks (Lehtovaara 1995). adopted from Norway. The allochthonous units

101 Geological Survey of Finland, Bulletin 412 Jouni Luukas and Jarmo Kohonen

Table. 7. Tectonostratigraphic units of the Kilpisjärvi Structural Province.

Unit name Sole thrust Main references Lithostratigraphic / Lithodemic units Finnish Caledonides thrust system

Vaddas Nappe Vaddas-Corrovarri thrust (decollement of Lehtovaara 1989, 1995 Ridnitsohkka gabbro sill the Upper Allochthon) Nabar Nappe Nabar thrust zone Lehtovaara 1989, 1995 Pihtsosnjunni muscovite gneiss, Kovddoskaisi amphibolite Nalganas Nappe Nalganas sole thrust (decollement of the Lehtovaara 1989, 1995 Saana arkose quartzite Middle Allochthon)

4 TIME CONSTRAINTS OF THRUSTING

4.1 General

The abundance of thrusts and the overall structural ent. The formation of the Svecofennian crust lasted style of the Karelia Province have been well described, more than 100 Ma (ca. 1.93–1.81 Ga), and even the but the areal extent of the observed structural over- major structural features are poorly dated. The early printing is for the first time presented as structural thrusts within the Svecofennian province are dis- provinces by Kohonen et al. (2021). The tectonic continuous, reoriented and reactivated structures model and the set-up of the collision zones border- mainly inferred from lithological relationships. ing the Karelia province advanced gradually through In the light of the prevailing tectonic models (e.g. the milestones provided by Gaál & Gorbatchev Lahtinen et al. 2005), it appears that during the (1987), Nironen (1997), Lahtinen et al. (2005) and main magmatic stage (ca. 1.89–1.86 Ga), the rhe- Lahtinen & Huhma (2019). Nevertheless, many ology of hot juvenile crust was not favourable for questions are still to be resolved, and major issues localizing deformation in thrust zones and crustal include: (1) the kinematic and thermal evolution thickening by thrusting (see discussion by Hölttä of the ‘Raahe–Ladoga zone’ (RLZ) from the early et al. 2020). collision zone (the Raahe–Ladoga suture) to a dex- Data concerning the age of different structures tral transcurrent shear system, (2) details of the is sparse and their correlation requires sophisti- Norrbotten–Karelia relationships, including the cated interpretation (e.g. Nironen 2017). The overall kinematic evolution and the timing of the structures dynamic and kinematic model covering the evolu- from collision-related thrusting to the development tion from the main collisions along the sutures (ca. of the Kolari–Pajala shear zone, (3) the tectonic 1.9 Ga) to the voluminous Svecofennian granitoid model for the deep burial and subsequent uplift of magmatism (ca. 1.89–1.86 Ga) and further to the the Lapland granulite belt (Inari allochthon in the crustal reactivation (ca. 1.84–1.81 Ga) in the south- structural nomenclature) and, finally, (4) the tim- ern Finland is still unclear, and many controver- ing and interaction of the Western Lapland and the sial ideas have been proposed. The construction of Northern Lapland thrust systems. a comprehensive age classification of thrusts and In comparison to the cratonic foreland, the other structures was not found possible. Instead, Karelia Province, the Svecofennian deformation we present a collection of key data, a brief sum- style of the Central Finland and Southwestern mary and a tentative division (Fig. 9) based on our Finland Provinces (Fig. 4) is fundamentally differ- interpretation.

102 Geological Survey of Finland, Bulletin 412 Major thrusts and thrust-bounded geological units in Finland: a tectonostratigraphic approach

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Fig. 9. A simplified map addressing the approximated age groups of the major thrusts and shear zones. The geological background map is simplified from Nironen et al. (2016).

103 Geological Survey of Finland, Bulletin 412 Jouni Luukas and Jarmo Kohonen

4.2 Main collision stage within the Karelia tectonic province ca. 1.93–1.90 Ga

The upper age limit of the earliest deformation the Ylitornio allochthon, a maximum age of 1.91 of the Raahe–Ladoga thrust system is provided was suggested by Lahtinen et al. (2015a). This is by the sedimentary rocks within the Vieremä in accordance with the estimated thrusting age of (Salahmi area) and Kiuruvesi (eastern Kansanneva around 1.92–1.90 Ga interpreted from metamor- and Loutemäki areas) allochthons, with maximum phic zircons (Lahtinen et al. 2018). We assume depositional ages constrained by the detrital zircons that the development of all the decollements below at 1.92–1.91 Ga (Lahtinen et al. 2015b). The end of the Kittilä, Ylitornio and Rovaniemi allochthons the thrusting stage within the Raahe–Ladoga suture roughly corresponds to that age. zone can be deduced from the deformation of the According to Lahtinen & Huhma (2019), the Kola– early structures, with suggested minimum ages of Lapland Structural Province represents a retroarc fore- 1.89 Ga (by Hölttä 1988 and Korsman et al. 1999) land thrust belt. The major thrusting phase occurred and 1.88 Ga (by Lahtinen et al. 2015b). ca. 1915–1910 Ma ago and the crustal shortening Along the Kautokeino–Muonio–Tornio suture continued until ca. 1870 Ma. Nevertheless, the zone, the deformation history and kinematics of tectonic and metamorphic evolution of northern thrusting are poorly constrained and partly con- Lapland is not fully resolved, and especially the troversial (e.g. Lahtinen et al. 2015a, 2018, Skyttä kinematics and timing of the individual thrusts are et al. 2019, Piippo et al. 2019). The methods for the open to speculation. detailed dating of structures are limited, but for

4.3 Evidence for thrusting between 1.89–1.86 Ga

The details of the kinematic evolution of the Raahe– Piippo et al. (2019) presented an elegant struc- Ladoga suture zone from collisional deformation and tural model for the Peräpohja belt (S of the Ylitornio crustal shortening to a nearly vertical system of allochthon). The model involves folding and asso- transcurrent faults are poorly known. According to ciated S-vergent thrusts, and the authors point the Pielavesi case study (Woodard et al. 2017), the out the importance of the paleotopography of the syn-kinematic granitoids, with ages around 1885 Archean basement blocks as the major controlling Ma, were emplaced in relation to a vertical dextral factor regarding the orientation of structures. Both shear zone, and no indication of further thrusting the age of the reported thrust structures and kin- was reported. We tentatively suggest an approxi- ematic connection to the Western Lapland thrust mate age of around 1.88 Ga for the generation of system remain open. some major shear zones (e.g. Ruhanperä, Suvasvesi, Tuisku et al. (2006) and Lahtinen & Huhma Haukivesi; Figs. 4 and 9). We see no evidence for (2019) assume that the Northern Lapland thrust collision-related thrusting younger than 1.89 along system represents two-stage evolution, with the the Raahe–Ladoga suture zone, within the entire main collision followed by a repeated shortening Svecokarelia structural province and in the northern phase ca. 1880–1870 Ma ago. They correlate the parts of the Central Finland tectonic province. deformation with the shortening reported in central The development of the Western Lapland thrust Lapland (D3 of Lahtinen et al. 2018) and connect the system along the Kautokeino–Muonio–Tornio deformation to collisions within the Svecofennian suture contains many uncertain and controversial arc complex further to the SW. In practice, we find aspects. Lahtinen et al. (2015a, 2018) and Sayab et the distinction between the early thrusts and these al. (2019) involve N–S and NE–SW-oriented short- younger thrusts (mainly reactivating early thrusts) ening from ca. 1.90 to 1.87 Ga. Sayab et al. (2019) challenging at the regional scale in Lapland. theoretically model in the Kittilä district some In the tectonic model by Lahtinen et al. (2005), thrusts (e.g. the initiation of the Sirkka and Venejoki the Southwestern Finland tectonic province represents thrust zones) to this stage. The major Hirvaskoski a juvenile arc collage laterally accreted along the shear zone (Fig. 5), which is transected by the Auho present Bothnia–Pirkanmaa Suture to the previ- fault (part of the Oulujärvi shear zone; see Kärki et ous Central Finland arc collage ca. 1.88 Ga ago. In al. 1993) and connected to the Kemijärvi shear zone, the southern parts of the Central Finland tectonic may also have originated around 1.88 Ga ago. province and in southern Finland, all the early

104 Geological Survey of Finland, Bulletin 412 Major thrusts and thrust-bounded geological units in Finland: a tectonostratigraphic approach structures, including the Leivonmäki–Tampere– structures is expected to correspond to that of the Kankaanpää, Otava–Hämeenlinna–Kynsikangas collision. Without any firm evidence, we tentatively and Hyvinkää–Kisko shear zones, are severely support the overall model of Nironen (2017), and affected by later deformation (e.g. Väisänen & Hölttä propose a thrust origin followed by (repeated?) 1999, Pajunen et al. 2008, Mikkola et al. 2018). No reactivation as subvertical transcurrent shear zones detailed age data concerning the early deformation for many of these structures (Fig. 4). are available, but in principle, the age of the early

4.4 Proterozoic thrusts and deformation younger than 1.86 Ga

Regarding the younger thrust faults, it is appro- represent the margin of the rigid Venejoki block priate to include vertical shear zones in the over- transported towards the north ca. 1.8 Ga ago. Some all picture (Fig. 9). Both in central Lapland and in N–S-oriented structures in western Lapland (see central Finland, the youngest Paleoproterozoic (ca. the map by Nironen et al. 2016) indicate thrusting 1.83–1.79 Ga) dip slip faults are intimately linked of older rocks on the Kumpu group, with maximum with the adjacent strike-slip shear zones (Kousa & depositional age of 1.88 Ga (Köykkä et al. 2019). We Luukas 2007, Bergman & Weihed 2019). tentatively link these thrusts to the development of Within the Karelia tectonic province, one key struc- the Pajala deformation belt. ture is the Kolari–Pajala shear zone (Pajala Shear The age of major thrust faults bordering the Zone of Kärki et al. 1993), which approximately fol- blocks (Perho, Kauhajoki, Sulkava) in central lows the Kautokeino–Muonio–Tornio suture zone and Finland can definitely be bracketed by cross-cutting forms the eastern part of the wider Pajala deforma- relationships as younger than 1.88 Ga. The age of tion belt (cf. Luth et al. 2018, Bergman & Weihed the structures is not known, but it is assumed that 2019). The shear zone has a long tectonic history, the formation of crustal-scale thrusts necessitates starting from the collision followed by dextral strike advanced cooling of the juvenile Svecofennian crust, slip movement (Berthelsen & Marker 1986) and and therefore we estimate that these structures finally the sinistral transcurrent fault phase. The were plausibly generated not earlier than 1.83 Ga. age of the youngest fault generation with consid- A similar age approximation for the Sulkava block erable displacement is around 1.78 Ga or even later was proposed by Korsman et al. (1988). (Bergman & Weihed 2019). The Kolari–Pajala shear In southern Finland, the ductile deformation zone is linked to the southward-dipping Venejoki occurred in several phases between 1.85 and 1.79 Ga and Sirkka thrust zones, and both structures are (e.g. Torvela & Ehlers 2010). According to Väisänen & identified in the interpretation of the seismic line Skyttä (2007), the major, vertical shear zones within FIRE 4 (Patison et al. 2006). The Sirkka thrust zone the Southwestern Finland tectonic province developed deforms the Nuttio–Seurukarkea decollement at the after the main ductile deformation, peak metamor- southern margin of the Kittilä allochthon (Fig. 7). phism and crustal melting at 1840–1810 Ma. We suggest that the Sirkka and Venejoki thrusts

4.5 Paleozoic thrusting related to the Caledonian orogeny

The Kilpisjärvi structural province represents a tiny ca. 425–400 Ma ago (e.g. Roberts 2003, Gee et al. fragment of the frontal part of the Scandinavian 2008). Major thrusting occurred late in the Silurian, Caledonide Orogen. Caledonian continent–conti- with emplacement of the Caledonian orogenic wedge nent collision took place (further to the W) in the across the foreland basin in the Early Devonian (see Scandian phase (also termed the Scandian Orogeny) Gee & Stephens 2020 and references therein).

105 Geological Survey of Finland, Bulletin 412 Jouni Luukas and Jarmo Kohonen

5 CONCLUDING REMARKS AND SUMMARY

5.1 Nature of Paleoproterozoic thrust belts in Finland

In many orogenic belts, such as the Scandinavian nation of major structures, kinematic interpretation Caledonides, the tectonostratigraphic procedure is a and timing of both the deformation and regional well-established element of the mapping tradition. metamorphism. Presently, such detailed recon- However, even in the Precambrian of Finland, map structions are not possible, but we use the inten- unit division based on thrust planes also offers a sively studied southern part of the thrust system useful tool complementing the traditional lithol- (see Sorjonen-Ward 2006 and references therein) ogy–lithostratigraphy–based method. Informative as an example to discuss the thrust systems of the descriptions of Paleoproterozoic collisional belts Karelia province. Crustal thickening and deep burial with nappe tectonics, such as the Trans-Hudson of the cover rocks is evidenced by amphibolite facies Orogen (Lewry et al. 1994, Irvine et al. 2005), are (or higher) peak metamorphism (see the review by available, but ready-for-comparison models for the Hölttä & Heilimo 2017). The metamorphic observa- deep level of foreland thrust systems and structions (Säntti et al. 2006, Hölttä & Karttunen 2011) tures are sparse. Therefore, the application of thrust indicate late- to post-tectonic pressures corre- systems to metamorphic rocks in Finland needs to sponding to a minimum depth of ca. 20 km for the be accompanied by a discussion of the geological rocks of the Outokumpu allochthon. The eastern context. Tohmajärvi–Nunnanlahti–YläLuosta thrust stack The Proterozoic thrust systems in Finland rep- is characterized by medium-grade metamorphic resent deep sections of foreland fold-and-thrust conditions and by basement-involved thrusts belts. The work raised some questions regarding with coeval or successive ductile deformation. The the applicability of some standard FTB concepts and parautochthonous quartzites below the thrust stack terminologies. In the characterization of thrust sys- indicate metamorphism at a depth of around 15 km tems, the main parameters to be considered are: (Hölttä & Heilimo 2017). (1) the distance from the collision zone (internal Even considering that the indicated pressures do vs. external FTB) and (2) the depth in the thrust not correspond to the main thrusting stage, and pile (Fig. 10). The minimum distance from the col- that the depths as such may be overestimated, it is lision zone can somehow be figured out based on obvious that the development of the present North the location of suture zones (see Fig. 3), but major Karelia–Kainuu thrust system reached conditions uncertainties remain. For example, regarding the that are not comparable to examples and concepts Northern Lapland thrust system, the location of the derived from external, shallow thrust belts. Ramp- suture separating the Kola and Karelia provinces is flat geometries and other features typical for exter- poorly defined, and the overall tectonic model of the nal parts of a thrust belt are not identified, and the collision is controversial (e.g. Patison et al. 2006, detached allochthonous units are characterized by Lahtinen & Huhma 2019). ductile deformation with tight to isoclinal folding The assessment of depth is a complicated issue. (e.g. Outokumpu allochthon; Koistinen 1981). The The metamorphic peak conditions are mostly transition towards the internal crystalline core of reached well after the main thrusting stage. the orogen is first indicated by intensified recrys- Furthermore, the common metamorphic assem- tallization with increasing metamorphic grade blages are not very sensitive to pressure, and only and finally by transition to migmatites and intru- general estimates (e.g. low pressure vs. medium sive bodies obscuring the previous thrust-related pressure) are typically presented. The main diffi- structures (Fig. 10). In deep levels of a thrust belt, culty arises, however, from the thrusting process as even the distinction of structures related to pro- such: a thrust system migrates towards the foreland gressive thrusting and later ductile folding has not (the externides) and thickens by piling (the inter- been straightforward (e.g. Koistinen 1981, Ward & nides) at the same time. During the long FTB evolu- Kohonen 1989, Kohonen 1995), and the causal and tion, the thrust zones have been active in different temporal connection of the thrusts in different parts P/T conditions before the peak metamorphism. of the system has remained unclear. The integration of thrust systems into the tectonic deformation history would require the combi-

106 Geological Survey of Finland, Bulletin 412 Major thrusts and thrust-bounded geological units in Finland: a tectonostratigraphic approach

Fig. 10. The assumed approximate positions of the present North Karelia–Kainuu (red ellipse) and Finnish Caledonides (blue ellipse) thrust systems within a simplified and generic foreland fold-and-thrust belt model. (Model modified after Hatcher & Williams 1986).

The North Karelia–Kainuu thrust system shows basement–cover relationships, such as basement- substantial crustal shortening/thickening, which cored overturned anticlines and narrow cover out- is possible to explain via crustal-scale “thick- liers within the basement complex, are difficult to skinned” imbrication plausibly preceded by “thin- explain without ductile basement behaviour, in cer- skinned” nappe emplacement (e.g. Kohonen 1995). tain zones at least. Evidence of ductile deformation However, considering the tectonically deeply buried of the basement–cover interface raises not only the setting of the thrust system, the strict division into thin/thick-skinned issue, but also questions about thin/thick-skinned deformation styles can also be the overall deformation style and applicability of questioned. In medium-grade metamorphic condi- terms such as decollement in relation to the defor- tions, both the cover rocks and the basement com- mation style characterized by fold-thrust uplifts plex have reached conditions where the rheological with tight asymmetric folding rather than definite contrast between them may no longer be distinct. In thrust planes. addition, the lower parts of the supracrustal cover Regarding the future research challenges, the (typically quartzites) are welded to the basement by major question within the entire Karelia tectonic a network of gabbroic dykes (‘Jatulian diabases’). province is the overall style of the basement- Consequently, the major rheological contrast may involved deformation. The previous interpreta- occur at the upper boundary of the dyke system, tions are highly variable, from models assuming or some other place within the sequence, and not imbrication of thin basement slivers (e.g. Park & necessarily at the basement–cover interface, as Doody 1991, Koistinen 1993) to semiductile base- presumed in thin-skinned modelling. ment-cored anticlines (e.g. Kohonen 1995). Better The basement deformation is currently poorly knowledge of both the style and location of the studied, and one major challenge is the recogni- major basement-involved thrusts is essential for tion of the crystalline thrusts (cf. Hatcher 1995) improved thrust system modelling. Only detailed within the basement areas; although the thrusts studies (such as Evins & Laajoki 2002), including are plausibly present, the lack of marker horizons kinematic indicators within the shear zones, would makes them difficult to recognise. The observed substantially help in solving this problem.

5.2 Comments on the selected approach

The justification and practical need behind the theory behind our approach is the general scientific presented approach is the conclusion that in many knowledge of thrust belts and their internal struc- cases, tectonic processes have completely rear- tures. Coupling of tectonic models, thrust system ranged the primary rock units, and the structural concepts and the observed features, such as fault features dominate the resulting bedrock map. The zones and different lithologies, opens the inter-

107 Geological Survey of Finland, Bulletin 412 Jouni Luukas and Jarmo Kohonen pretation process, finally leading to the establish- example of this difficulty was the classification of ment of thrust-bounded map units (Fig. 11). The the Peräpohja belt. The cross-section provided by thrust-bounded units are, by definition, based on Piippo et al. (2019) indicates local thrusting and their bounding structural contacts (sole thrust / even features of considerable tectonic transport. roof thrust). In practice, however, the identification However, the stratigraphy is still readable, and of bounding surfaces is affected by the lithologi- at this stage the belt was classified as part of the cal units and their relationships with each other. parautochthonous cover. Due to the method, the resulting units are heavily The compilation of the cross-section across the dependent on the judgment of the authors. Central Lapland belt (Fig. 8) brought up the chal- We have presented the thrust-bounded units as lenges of 3D modelling. Information concerning map polygons. The areas not included in thrust- both the subsurface detachments and internal bounded units (within the Karelia tectonic prov- geometries of the thrust-bounded units is limited to ince) represent either intact Archean basement a simple projection of surface structures with some rocks or parautochthonous cover rocks. The term support provided by the interpretation of seismic ‘parautochthonous’ is fuzzy by definition, and in lines, geophysical data and, in places, by drilling reality the cover rocks are deformed everywhere: results. Thrust zones are potentially more com- the quartzites in North Karelia are imbricated, the plex than planes: blind thrusts, fold thrusts, horses Kuusamo belt is multiply folded and the boundary and complex duplex geometries can be presumed. between the Sodankylä thrust stack and the sur- An example is the indefinite frontal thrust of the rounding fold belt is arbitrary. Our guiding rule Tohmajärvi–Nunnanlahti–YläLuosta thrust stack was that when thrusting has markedly mixed up (see Table 1). The assumed detachment zone can the superposition of primary units, the application be described as an anastomosing network of shear of thrust-bounded units is justified. However, full planes rather than one continuous thrust plane. It consistency in the case-by-case definition of the appears that 3D modelling of thrust planes in struc- boundary between a thrust stack and parautoch- turally complex regions, such as southern Finland, thonous cover has probably not been achieved. An will be a very demanding task.

Observation Conceptual framework

Structural field measurements Remote sensing data • Local structural characteristics Geophysical data • Structural relationships (D1-Dn) Structural planes Regional interpretation Litho-unit boundaries • Structural characteristics • Structural sequence (D1-Dn) Structural unit boundaries Structural provinces Interpretation Structural domains

Tectonostratigraphic / thrust-bounded units Tectonic provinces

Tectonic modelling

Fig. 11. The complex relationships of observed geological features, interpretations and the overall tectonic framework in the formation of thrust-bounded map units; the map unit categories included in the GTK map data architecture are shown as framed boxes.

108 Geological Survey of Finland, Bulletin 412 Major thrusts and thrust-bounded geological units in Finland: a tectonostratigraphic approach

5.3 Summary

In geology, the final output (e.g. map, model) is 1. A systematic, country-wide arrangement of all highly dependent on the underpinning conceptual the thrust-bounded map units is presented for framework, consisting of theories, models, classi- the first time. Tectonic and structural provinces fication rules and research tradition. The national have been utilized as the framework for the conceptual framework also needs maintenance. division. From time to time, the field observation-based 2. The presented nomenclature is one step towards bottom-up method needs to be complemented by a more harmonized science-language in Finland. holistic top-down approach by reviewing the state- 3. The units within the Raahe–Ladoga thrust sys- of-the-art. We see that the systematic arrangement tem represent Svecofennian orogenic rocks, and of structural map units is of growing importance the Kiuruvesi allochthon was tectonically trans- and part of a functional geological framework. ported on the Archean crust. The definition of the This work is the first attempt to create an over- thrust system simplifies the description of the all tectonostratigraphic scheme in Finland. With complex Raahe–Ladoga suture zone. progressing research, many of the presented unit 4. The presented cross-section with thrust-bounded boundaries will be relocated and new units pre- map units offers an explanation for some strati- sented. Basically, the thrust-bounded map units graphic questions in Central Lapland (Sodankylä can be seen as a bridge between the conceptual area). tectonic models (such as schematic crustal cross- 5. The results will aid in the construction of both sections, tectonic provinces and suture zones) and advanced 3D models and more traditional depo- mapped real-world features, such as structures and sitional/stratigraphic models in different parts lithostratigraphic units. of Finland. The main outcome and highlights of our work can be summarized as follows:

ACKNOWLEDGEMENTS

We are grateful to Stefan Bergman and Markku Lahtinen and Mikko Nironen made suggestions for Väisänen for their firm and constructive reviews, the early version, and Anneli Lindh assisted with which helped us to consolidate the manuscript the figures. and reconsider some terminological issues. Raimo

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Fennia, 50 (16). zoic Central Lapland Greenstone Belt of Fennoscan- Woodard, J., Tuisku, P., Kärki, A., Lahaye Y., Ma- dia: constraints from the world-class Suurikuusikko jka J., Huhma, H. & Whitehouse, M. J. 2017. Zircon gold deposit. Mineralium Deposita. Available at: and monazite geochronology of deformation in the https://doi.org/10.1007/s00126-019-00910-7 Pielavesi Shear Zone, Finland: multistage evolution of Schmidt, C. J. & Perry, W. J. (eds) 1988. Interaction of the the Archaean – Proterozoic boundary in the Fennos- Rocky Mountain Foreland and the Cordilleran Thrust candian Shield. Journal of the Geological Society, Vol. Belt. Geological Society of America Memoir 171. 582 p. 174, 255–267. Available at: https://doi.org/1 Skyttä, P., Piippo, S., Kloppenburg, A. & Giacomo Corti, G. 2019. 2. 45 Ga break-up of the Archaean continent

113 Geological Survey of Finland, Bulletin 412 Jouni Luukas and Jarmo Kohonen

114 Developments in map data management and geological unit nomenclature in Finland Edited by Jarmo Kohonen and Timo Tarvainen Geological Survey of Finland, Bulletin 412, 115–169, 2021

CLASSIFICATION SYSTEM FOR SUPERFICIAL (QUATERNARY) GEOLOGICAL UNITS IN FINLAND

Jukka-Pekka Palmu1*), Antti E. K. Ojala1), Joonas Virtasalo1), Niko Putkinen2), Jarmo Kohonen1) and Pertti Sarala3)

Palmu, J.-P., Ojala, A. E. K., Virtasalo, J., Putkinen, N., Kohonen, J. & Sarala, P. 2021. Classification system of Superficial (Quaternary) Geological Units in Finland.Geological Survey of Finland, Bulletin 412, 115-169, 14 figures, 4 tables and 2 appendices.

The emergence of digital map processing and interpretation environments, including advanced tools for 3D modelling and forward modelling, has created a demand for easy access to well-organized geological map data. At the same time, the interpretation of LiDAR DEM imagery with high spatial resolution has revolutionized the production of new Quaternary mapping in greater detail than hitherto. As a consequence, the need for an improved arrangement and coherent terminology for the superficial geological units is apparent. Here, we present an upgraded classification system for Quaternary superficial geological units in Finland. The main emphasis is on the management of regional-scale map units and their connection to local lithostratigraphic type sections and units.

The present document outlines the new digital lexicon (FinstratiMP) in Finland. We divide the superficial units according to four parallel classification systems: (1)glacial dynamic province/region classification, (2) morpho-lithogenetic (MLG) classification, (3) lithostratigraphic classification, and (4) allostratigraphic classification. The four parallel systems cover the needs of regional to local scale mapping, as well as detailed research describing the genetic relationships of geological units in vertical sections.

This document also updates the division of major glacial dynamic Quaternary map units in Finland and defines the use and mapping procedures of morpho-lithogenetic units and classification. Theglacial dynamic units (provinces and regions) are geological map units based on their interpreted glacial dynamic settings in Finland. The glacial dynamic ice lobe provinces reflect the movements of ancient ice sheets, the most significant agents of glacial erosion, transportation and deposition. The glacial dynamic regions correspond to passive ice areas that are located in between relatively fast ice flow areas. Theglacial dynamic units are defined as major geological map features (units) with glacial dynamic characteristics different from the adjacent units. The units are identified based on the characteristics of morpho-lithogenetic (MLG) assemblages.

The glacial dynamic unit-based approach creates the overall framework for depositional models, whereas the morpho-lithogenetic classification is useful in the production of new interpreted map data from LiDAR DEM imageries. Lithostratigraphy and allostratigraphy are standard methods in type section-based mapping and classification categories based on lithological characteristics and stratal discontinuities. The combined use of the different classifications provides a powerful toolbox for the management of the Quaternary superficial geological units in Finland.

Keywords: glacial features, Quaternary, stratigraphic units, surficial geology maps, databases, superficial deposits, superficial geological units

115 Geological Survey of Finland, Bulletin 412 Jukka-Pekka Palmu, Antti E. K. Ojala, Joonas Virtasalo, Niko Putkinen, Jarmo Kohonen and Pertti Sarala

1) Geological Survey of Finland, P.O. Box 96, FI-02151 Espoo, Finland 2) Geological Survey of Finland, P.O. Box 97, FI-67101 Kokkola, Finland 3) Geological Survey of Finland, P.O. Box 77, FI-96101 Rovaniemi, Finland

* Corresponding author, e-mail: [email protected]

https://doi.org/10.30440/bt412.4

Editorial handling by Timo Tarvainen. Received 16.10.2020; Received in revised form 12.4.2021; Accepted 13.4.2021

116 Geological Survey of Finland, Bulletin 412 Classification system of Superficial (Quaternary) Geological Units in Finland

CONTENTS

1 INTRODUCTION...... 118

2 THE QUATERNARY OF FINLAND: DEPOSITIONAL FRAMEWORK...... 119

3 CLASSIFICATION OF SUPERFICIAL DEPOSITS IN FINLAND...... 121 3.1 Geological unit – the fundamental building block in geological description...... 121 3.2 Applicability of geological unit classification systems in Finland; an overview...... 122

4 SUPERFICIAL GEOLOGICAL UNITS IN FINLAND...... 124 4.1 Glacial dynamic map units: provinces and regions...... 124 4.1.1 General...... 124 4.1.2 Definition of glacial dynamic provinces and regions (GD units)...... 124 4.1.3 Ice-lobe provinces...... 126 4.1.4 Interlobate regions, fell regions and the ice-divide zone...... 126 4.2 Morpho-lithogenetic units (MLG units)...... 127 4.2.1 General...... 127 4.2.2 Morpho-lithogenetic map units; definition of genetic deposit type...... 128 4.2.3 Establishment of morpho-lithogenetic geological units ...... 129 4.2.4 Major MLG units in Finland...... 131 4.3 Lithostratigraphic units...... 135 4.3.1 General...... 135 4.3.2 Lithostratigraphic units in Finland ...... 136 4.4 Allostratigraphic units ...... 138 4.4.1 General...... 138 4.4.2 Allostratigraphic units in Finland...... 139

5 SUMMARY AND IMPLICATIONS...... 139

ACKNOWLEDGEMENTS...... 141

LIST OF APPENDICES...... 141

REFERENCES...... 141

APPENDIX 1 ...... 145

APPENDIX 2 ...... 152

117 Geological Survey of Finland, Bulletin 412 Jukka-Pekka Palmu, Antti E. K. Ojala, Joonas Virtasalo, Niko Putkinen, Jarmo Kohonen and Pertti Sarala

1 INTRODUCTION

Superficial Quaternary deposits in Finland are The renewed interpretation process for superfi- dominated by tills and different types of moraines cial deposits maps is complemented by the develop- and glaciofluvial deposits, which were later partly ment of modelling (2.5D and 3D) activities (cf. Ojala covered by postglacial fine-grained sediments and et al. 2018a, Kohonen et al. 2019). 3D modelling is peat. The challenges in the classification of the gradually becoming mainstream in the depiction Quaternary deposits in Finland are manifold. The and conceptualization of geology. The modelling classification scheme should serve, for example, the process incorporates different spatial datasets (e.g. practical needs for regional-scale geological map- geological maps, vertical sections, underground ping, the requirements of more detailed mapping surfaces) with various terminologies and classifi- and 3D modelling, and science-oriented research cations. The merging of data would greatly benefit approaches. Formal stratigraphic categories and from harmonized classification rules, procedures procedures (Salvador 1994, McMillan et al. 2011) and vocabularies for the geological units. have been found insufficient as the only system in Finstrati was originally designed as the strati- the definition of Quaternary map units (see Chapter graphic database for lithostratigraphic/lithodemic 3.2 and references therein). bedrock units (see Luukas et al. 2017). Gradually, In this document, we present principles for the the scope was enlarged towards a lexicon and classification and division of the superficial geo- national key reference to all geological units and logical units in Finland. The main emphasis is on the linked vocabularies. Currently, Finstrati con- the management of regional-scale map units and sists of two domains: FinstratiKP for the bedrock in their connection to local lithostratigraphic type units and FinstratiMP for the superficial deposits. sections and formations within. The need for an The main aim of the present document is to define upgraded classification system of superficial depos- and construct the FinstratiMP but at the same time its in Finland arises from three progress areas: (1) also defining the concepts and classifications for the systematic survey and classification of map the geological unit categories (see Chapter 3 and 4) units interpreted from LiDAR DEM imagery, (2) the for morpho-lithogenic, glacial dynamic, lithostrati- management of different spatial data sets in the 3D graphic and allostratigraphic units. This document forward modelling process and (3) the development provides tools for the practical management of of the national geological unit lexicon (Finstrati). superficial geological units in Finland, including With the emergence of LiDAR DEM imagery, the interpreted (conceptual) units and the map- the mapping process for superficial geology at the pable lithology-based or surface-bounded units. Geological Survey of Finland (GTK) was completely The envisaged application areas that will benefit renewed (see Putkinen et al. 2017). The traditional, from the FinstratiMP include regional and nation- superficial deposits, partly lithology-based map- wide geological map compilations, stratigraphic ping method (1:20 000 map sheets, Haavisto- interpretations and correlations, data modelling/ Hyvärinen & Kutvonen 2007) was replaced by database design, 3D modelling and Quaternary glacial terrain mapping, including the dynamics of research. The classification principles, terminology the Fennoscandian Ice Sheet (FIS), also known as and nomenclature presented in this document are a the Scandinavian Ice Sheet, during the Weichselian. part of the Finstrati documentation, which will be Consequently, the map units of the superficial updated with the developing concepts of superficial deposits need to be consistent with the dynamics deposits mapping in Finland. and evolution of the FIS.

118 Geological Survey of Finland, Bulletin 412 Classification system of Superficial (Quaternary) Geological Units in Finland

2 THE QUATERNARY OF FINLAND: DEPOSITIONAL FRAMEWORK

The relatively thin, unconsolidated sedimentary cesses during the Late Quaternary glacial-intergla- cover overlying the Precambrian bedrock is gener- cial cycles (Fig. 1) and especially during and after ally termed superficial deposits or, when especially the last (Weichselian) glaciation (e.g. Johansson et regarding the time, Quaternary deposits in Finland. al. 2011). The Late Weichselian to Holocene depos- The Quaternary period represents the last 2.7 mil- its are the most abundant superficial deposits in lion years (Gibbard & Cohen 2008, Cohen & Gibbard Finland, whereas the pre-Weichselian sediments 2011); most of these deposits in Finland are Late are only preserved locally as remnants, most com- Weichselian to Holocene in age. The term superficial monly in northern Finland (Fig. 1). Since the last is used here to emphasize features immediately at deglaciation, postglacial clastic deposition in aeo- the land surface (cf. surface geology vs. subsurface lian, lacustrine, shoreline and fluvial environments geology; Neuendorf et al. 2005 (Glossary of Geology has continued, and thick organic sediments (peat) 2005)). have accumulated in bogs (see Table 1). The superficial deposits in Fennoscandia were deposited by various glacial and postglacial pro-

Fig. 1. A schematic illustration of Quaternary superficial deposit occurrences in Finland and their relation to geological time. In southernmost Finland the superficial deposits are mostly form Late Weichselian and Holocene, whereas in parts of Lapland are relatively much older Quaternary deposits. See also Cohen & Gibbard 2020: https://stratigraphy.org/ICSchart/QuaternaryChart1.jpg.

Glacial deposits comprise the primary glacial and gravel, sand and silt, and often constitute the thick- glaciofluvial sediments of the Weichselian and ear- est accumulations of superficial deposits in Finland lier glaciations. Earlier interglacial and interstadial (e.g. Salpausselkä I, II and III ice-marginal systems; sediments are not considered as glacial deposits. also known as end-moraine systems). Glacial deposits are composed of different types The composition, structure, and occurrence of of tills (sediments) and moraines (formations), subglacial tills varies spatially due to differences in partially superimposed by glaciofluvial deposits topography, the subglacial deformable material type with diagnostic geomorphological features: eskers, and bedrock lithology, and the distribution of Late deltas, extensive ice-marginal deposits and hum- Weichselian ice lobes. They are occasionally covered mocky moraines. The locations of subglacial drain- by hummocky moraines, formed either subglacially age systems are composed of washed and sorted or less frequently on melting ice-marginal zones.

119 Geological Survey of Finland, Bulletin 412 Jukka-Pekka Palmu, Antti E. K. Ojala, Joonas Virtasalo, Niko Putkinen, Jarmo Kohonen and Pertti Sarala

Glaciofluvial deposits and moraines usually have have been applied to study these type of sedimen- complex depositional architectures and relatively tary sequences (Virtasalo et al. 2005, Virtasalo et al. low lateral connectivity; in contrast, some till beds 2014; see Chapter 4.3 and 4.4). show rather extensive lateral continuity and extent The most common postglacial sediments, rep- and can be used for stratigraphical purposes. resenting the last 10 000 years, include fluvial river The fine-grained basinal deposits represent sediments, coastal and aeolian sands, and lacus- the distal deposition during the glaciation (gla- trine sediments, such as organic-rich sediments ciolacustrine and glaciomarine), intermittent and silts. At present, almost one-third of Finland is interglacial and interstadial basin stages and the covered by peatlands. The minor, but stratigraphi- several post-glacial stages of the Baltic Sea basin cally important, interglacial and interstadial sedi- (i.a. Björck 1995, Virtasalo et al. 2014). Silt and clay ments have a scattered spatial occurrence with very deposits cover large areas of the present Baltic Sea restricted lateral continuity (Tornivaara & Salonen basin and coastal areas in Finland. Basinal depos- 2007). Most typically, these consists of sand, silt, its are normally laterally extensive and, and both clay, peat and other organic-rich sediments. lithostratigraphic and allostratigraphic approaches

Table 1. Features typical for the glacial and other superficial deposits in Finland.

Features Glacial deposits Basinal deposits Other non-glacial deposits (mainly postglacial deposits)

Typical lithology Diamicton, till, boulders, gravel, Silt, clay (minor organic-rich clay (Boulders), gravel, sand, silt, sand, silt / clayey organic-rich sediment) clay, also peat

Lower contact Diamicton, till, boulders, gravel, Variable, over or in-between Variable, over glacial on: sand, silt, or over Precambrian glacial sediments or over sediments or over bedrock Precambrian bedrock Precambrian bedrock

Typical deposits Varied, dominantly various types Varied, different types of sedi- Varied, different types and the inferred of glacigenic and glaciofluvial ments deposited in lake and of sediments deposited depositional environment sediments and marine environments in littoral, fluvial, aeolian processes deposits environments, organic sediments and mass movement sediments

Distribution and – The whole of Finland – Baltic Sea Finland coverage – Pre-Weichselian glacial units – Finland occur especially in South Ostro- – Post-glacial fine sediments, bothnia, Middle Ostrobothnia, especially in southern Northern Ostrobothnia, Central Finland Lapland and Eastern Finland

Thickness 0–150 m, typically 0–3–>10 m for 0–100 m, typically 0–10 m 0–100 m, till-dominated and 10–30–>100 m typically 0–5–>10 m in regions with glaciofluvial sediments

Age Pleistocene to Early Holocene Late Pleistocene to present Holocene to present (ca. 10 000 – 2.6 million years)

120 Geological Survey of Finland, Bulletin 412 Classification system of Superficial (Quaternary) Geological Units in Finland

3 CLASSIFICATION OF SUPERFICIAL DEPOSITS IN FINLAND

3.1 Geological unit – the fundamental building block in geological description

Geological unit is a generic term used in variety of is supported by defining all the new geological units meanings in different geological contexts. However, using an appropriate classification scheme. by definition (Fig. 2) a geological unit has bound- It is essential to recognize that different work aries, spatial properties (e.g. stratotype location, processes use and produce different geological map unit boundary coordinates) and geological unit information. For example, the compilation of characteristics. a national map legend progresses from the defini- A geological unit can be, for example, a map tion of the major map units reflecting the general unit, a stratigraphic unit in a vertical log/section or geological setting (or context) stepwise to smaller, a sediment body between the recognized bound- more detailed geological units. An opposite, bot- ing surfaces. The classification system is based on tom-up approach is the observation-based research classification rules in order to keep the system of process proceeding from detail observations to their units consistent and to enable the controlled use of interpretation and finally to the definition of the parallel unit classifications. Good scientific practice geological units.

Fig. 2. The definition of a geological unit in NADM-C1 documentation(North American Geologic Map Data Model Steering Committee 2004).

FinstratiMP, the GTK database of superficial depos- (Geologian tutkimuskeskuksen verkkopalvelu: its (see Ahtonen et al. 2021; this volume), will in Aineistot ja verkkopalvelut - geo.fi https://www. the future be the major source for information gtk.fi/palvelut/aineistot-ja-verkkopalvelut/) on Quaternary geological units in Finland. Other important sources of information are the STRATO • Published or accessible data from web services is database (Tornivaara & Salonen 2007) (see chap- available, for example, for: ter 4.3.2) and the GTK online information services. – lake sediments (i.a. Itkonen et al. 1999, Regarding the superficial deposits in Finland, abun- Pajunen 2004, Ojala & Alenius 2005) dant information is available: – peat deposits (i.a. Geologian tutkimus- • Quaternary geological mapping data at different keskuksen verkkopalvelu: Suot ja turvemaat scales including, for example: http://gtkdata.gtk.fi/Turvevarojen_tilinpito/ – glacial dynamic mapping data (Putkinen et al. index.html, Mäkilä 1997, Mäkilä et al. 2001) 2017) – fine (basinal) sediments (i.a. Gardemeister – various types of primary geological observa- 1975, Sahala 1987, Ojala et al. 2007, Geologian tional data (quarry sections and test pits, data tutkimuskeskuksen verkkopalvelu: Happamat from drillings and borings) sulfaattimaat http://gtkdata.gtk.fi/hasu/index. – analysis data (including ground geophysics) html). (Geologian tutkimuskeskuksen verkkopalvelu: Karttapalvelut https://www.gtk.fi/palvelut/ aineistot-ja-verkkopalvelut/karttapalvelut/)

121 Geological Survey of Finland, Bulletin 412 Jukka-Pekka Palmu, Antti E. K. Ojala, Joonas Virtasalo, Niko Putkinen, Jarmo Kohonen and Pertti Sarala

3.2 Applicability of geological unit classification systems in Finland; an overview

In Finland, a systematic national approach to the the framework of the FinstratiMP geological unit management of superficial geological units has database. The descriptive classifications include: been lacking. Several case studies (e.g. Hirvas 1991, (1) lithostratigraphic classification (cf. Salvador Sutinen 1992, Nenonen 1995, Bouchard et al. 1990, 1994, North American Stratigraphic Code; NACSN Sarala 2005, Lunkka et al. 2016) have applied strati- 2005) and (2) allostratigraphic classification (North graphic classificatioahokan. However, due to the American Stratigraphic Code; NACSN 2005). The general lack of meaningful, mappable glacial units proposed interpretative classification categories with reasonable lateral continuity and connectiv- are: (3) morpho-lithogenetic classification (McMillan ity, the use of standard lithostratigraphical prac- 2005, McMillan et al. 2005, 2011; this report) and tices have had a little value in regional Quaternary (4) glacial dynamic division (Putkinen et al. 2017; mapping. As a consequence, until the last ten this report). years, regional superficial mapping practices were The classification of geological units based on dominated by a surface lithology-based approach, different characteristics, boundaries and attrib- before the LiDAR data revolution (see chapter 1). utes (e.g. lithology, fossil content, geochemical The past 1:20 000 map-sheet programme classified characteristics, distribution and age) of rock strata the superficial sediments according to grain-size, still form the scientific and practical foundation sediment types and geomorphological features (cf. of the Finnish Quaternary stratigraphy. The strati- Haavisto-Hyvärinen & Kutvonen 2007). The result- graphic classification systems are based on interna- ing map units (polygons) were not defined, char- tionally accepted, standard rules and procedures. acterized and named as geological units. Instead, Stratigraphic units have a recognizable name (for- we are using the new glacial deposits mapping mal or informal), and the unit is defined by map- data as the basis for superficial deposits map unit pable characteristic features. The most commonly management. used stratigraphic categories in Quaternary geol- INSPIRE classification has been proposed to be ogy are lithostratigraphy, biostratigraphy, chron- used as the basis for superficial deposits geological ostratigraphy and allostratigraphy; the procedures unit classification, but it is so general that it cannot and respective unit terms for all these can be found be applied to here presented glacigenic deposit clas- in Salvador (1994), Murphy & Salvador (1998) and sification. In the INSPIRE classification for Natural the North American Stratigraphic Code (NACSN Geomorphologic Feature Types the glacial, glaci- 2005). ofluvial, glaciolacustrine and glaciomarine features A common stratigraphical practice is to divide are all combined to one group (code list value). vertical sediment successions in exposures and/or The superficial deposits in Finland are consid- bore-holes into stratigraphical units. The detailed ered as (formal) stratigraphic units and map units bottom-up description of vertical sections typi- (Fig. 3). The four parallel systems (categories) form cally begins with the identification of lithofacies

Fig. 3. Geological unit categories defined for the construction of the GTK FinstratiMP unit database.

122 Geological Survey of Finland, Bulletin 412 Classification system of Superficial (Quaternary) Geological Units in Finland and lithofacies associations, which form the basis (2011), McMillan et al. (2005) and McMillan (2005). for the architectural elements and depositional In this article, we introduce the GTK application models. Finally, the type sections (stratotypes) are of the original BGS approach (see Chapter 3.2. and documented and the stratigraphic units defined. Appendix 2). Seismic, seismoacoustic, ground-penetrating radar We also introduce a new category of geologi- and electrical resistivity tomography are most typical map units based on their interpreted glacial cal data in the interpretation of surfaces applicable dynamic setting. The fundamental unit, ice-lobe for allostratigraphic classification. In some cases, province, signifies the regional extent of the ancient allostratigraphy is also a useful method in the divi- active ice sheet. A glacial dynamic unit (province and sion of till beds (Räsänen et al. 2009 and Fig. 4). region) is here defined as a major geological map fea- The applicability and usefulness of the strati- ture (unit) with glacial dynamic characteristics that graphic tradition and classification systems in differ from the adjacent units. The movement of the Quaternary mapping has long been debated (e.g. ancient ice sheets (ice lobes) played a major role in McMillan & Merritt 2012, Boulton 2012 and ref- shaping the landscape and was the most significant erences therein), and both international (e.g. agent of erosion, transportation and glacial deposi- McMillan et al. 2005) and domestic (Räsänen et al. tion. The underpinning geological foundation is the 2009) alternative approaches have been suggested. history of the Fennoscandian Ice Sheet (e.g. Punkari Morpho-lithogenetic classification (MLG) is an infor- 1980, Donner 1995, Hughes et al. 2015, Stroeven et mal approach developed by the British Geological al. 2016, Putkinen et al. 2017). The glacial dynamic Survey (cf. McMillan 2005) to meet the practical map units correspond to glacigenic deposits of a needs of Quaternary mapping in the British Isles. certain glacial dynamic domain and are identi- McMillan et al. (2011) provide the following defi- fied by characteristic morpho-lithogenetic (MLG) nition: “Morpho-lithogenetic units are locally map- assemblages. Thus, the morpho-lithogenetic units pable sediment-landform assemblages which should with their genetic depositional interpretation form be considered without regard to time (Schenk & Muller a basis for glacial dynamic reconstructions with 1941, Salvador 1994). Some morpho-lithogenetic units the major ice lobes and the new glacial dynamic are not readily amenable to lithostratigraphic clas- map unit division. The principles and procedures sification because their stratigraphical relationships of glacial dynamic classification are introduced in the are poorly known.” The rationale and principles of Chapter 4.1. the MLG system can be found in McMillan et al.

Fig. 4. Schematic illustration addressing the connections of the different classification systems applied to map view (top centre), vertical strata (top right) and geological cross-section (bottom centre). Note the colour coding (top left) for the classification systems.

123 Geological Survey of Finland, Bulletin 412 Jukka-Pekka Palmu, Antti E. K. Ojala, Joonas Virtasalo, Niko Putkinen, Jarmo Kohonen and Pertti Sarala

Parallel classification categories are needed to jects. Through the flexible combination of different cover the variable practical needs, such as regional classifications, the Finnish superficial geology can mapping (feature catalogues, legends), the develop- be described in both a comprehensive and system- ment of a lexicon database (Finstrati data model) atic way; the overall idea is summarized in Figure 4. and the various aspects of Quaternary research pro-

4 SUPERFICIAL GEOLOGICAL UNITS IN FINLAND

In the following, the superficial geological units tems, drumlins and hummocky moraine fields, were in Finland are presented, starting from the gla- formed. Furthermore, the morpho-lithogenetic map cial dynamic regions and provinces, followed by units can, when appropriate, be complemented morpho-lithogenetic and stratigraphic units. The and combined with stratigraphic units (see Lee & glacial dynamic map units (regions and provinces) Booth 2006). For the local allostratigraphic and reflect the regimes where the morpho-lithoge- lithostratigraphic units, the MLG units provide a netic units, such as the Late Weichselian and Early depositional framework and a link to the overall Holocene ice-marginal deposits, main esker sys- depositional system (Fig. 4).

4.1 Glacial dynamic map units: provinces and regions

4.1.1 General mapping and (2) Quaternary scientific communication in Finland. It is essential to note that GD prov- Changes in ice flow systems at the ice sheet scale inces and regions represent conceptual, second-order represent readjustments to a changing glacier mass map units based on features interpreted according balance driven by climate, sea-level changes and to the MLG interpretation process. The MLG fea- ice sheet internal dynamics. As a whole, the glacial tures (e.g. drumlin fields and lineations, interlobate dynamic map units are a collection and synthesis eskers, and ice-marginal complexes) relate to a gla- of ice flow (stream) areas (ice-lobe provinces) and cial dynamic set-up at a certain geological time and the interlobate areas (regions) in between (Fig. 5). that the definition of time constraints is part of the In addition, a spatially imprecise ice-divide zone GD unit description. in Lapland has been outlined. Currently, 19 distinct The glacial dynamic province or region (map glacial dynamic map units (Fig. 5 and Appendix 1) unit) definition shall contain information related have been identified in Finland. We note, however, to all items described below and the description of that there are other earlier ice-lobe provinces their boundaries shall follow the guidelines given in related to Middle, Early and pre-Weichselian gla- Appendix 1, Table 1. The definition of a new lower- ciations that have not yet been mapped in detail. class unit of sub-province (domain) must include These provinces commonly occur in the Ranua the name of the parent unit. The glacial dynamic interlobate region, Kuusamo ice-lobe province map units are defined and characterized by the fol- and in central Lapland (Kolari-Kittilä-Sodankylä). lowing features and attributes: These older glacial dynamic map units are planned to be defined later. Glacial dynamic province/region geological map unit attributes 4.1.2 Definition of glacial dynamic provinces and The definition of the attributes list focuses on the regions (GD units) managing of the specific features of the individual units. There is no need to repeat in the attribute Glacial dynamic (GD) provinces and regions constitute fields the same information already incorporated the largest Quaternary map units in Finland (Fig. in the unit classification (glacial dynamic setting, 5) and form the overall conceptual, spatial and characteristic structural features). temporal framework for the superficial deposits in Geological age of the Glacial dynamic provinces Finland. The division was developed to meet the and regions is Late Weichselian and/or Holocene. needs of both (1) nationwide superficial deposits In the future, the aim is to add older (pre-Late

124 Geological Survey of Finland, Bulletin 412 Classification system of Superficial (Quaternary) Geological Units in Finland

Weichselian) GD spatial units; for these, the age is These consist of lineation and transport directions an essential attribute. and lengths in the active phase(s) and deglaciation Boundaries description includes their type, stage development as interpreted from the MLG nature and characteristics, for outer, lateral and units: esker system directions, hummocky moraine inner boundaries. Description of the status/nature field locations and characteristics, and the De Geer of the province/region as part of ice sheet-scale moraine and other recessional moraines fields ice-flow dynamics and deglaciation are important. and their characteristics. Older deposits (pre-late Description of the GD-unit-specific structural Weichselian) are also concisely described for the GD trends and patterns for ice-lobes includes the spatial units. Former names for the approximately zone of ice-marginal deposits and the ice lobe corresponding map unit are given and key refer- inner structure: drumlin fields (lineations), hum- ences are included. mocky moraine fields, meltwater routes and eskers.

Fig. 5. (A) The general ice-flow directions of various ages (blue lines; interpreted by Salonen 1986) and major ice-marginal positions (green lines) of the last deglaciation; province and region boundaries are shown as purple lines. (B) Glacial dynamic provinces and regions in Finland (modified from Putkinen et al. 2017); the Salpausselkäs and other major ice-marginal systems are shown as dark grey lines. Basemap © National Land Survey of Finland.

125 Geological Survey of Finland, Bulletin 412 Jukka-Pekka Palmu, Antti E. K. Ojala, Joonas Virtasalo, Niko Putkinen, Jarmo Kohonen and Pertti Sarala

4.1.3 Ice-lobe provinces Salla ice-lobe province (SIL) Inari ice-lobe province (IIL) The ice-lobe provinces form the backbone of the Enontekiö ice-lobe province (EIL) glacial dynamic division in Finland, and all the other GD unit types are defined by their relation to these. Ice-lobe province of the early Holocene: The scientific context and background of the ice- Näsijärvi–Jyväskylä ice-lobe province (NJIL) lobe provinces have developed from the pioneering work of Punkari (1980, 1997) through work by 4.1.4 Interlobate regions, fell regions and Salonen (1986), Lunkka et al. (2004), Johansson & the ice-divide zone Kujansuu (2005), Johansson et al. (2011) to the latest summary by Putkinen et al. (2017). Interlobate regions corresponds to a passive ice Ice lobe provinces correspond to an areas of area that is located between relatively fast ice-flow intense motion (flow) of a continental ice sheet. areas (i.e. ice-lobe provinces). An interlobate region The pattern of the predominant ice-flow direction is typically characterized by highly variable and is consistent in the entire ice lobe region. An ice- complex landforms. Older glacial and glaciofluvial lobe province is frequently laterally bordered by deposits and lineations have often been preserved large interlobate deposits (interlobate eskers and from earlier glaciations. Weak young lineations moraines) on both sides, and it often terminates may occur in some locations. Fell regions (highland distally in well-developed ice-marginal complexes interlobate region) correspond to higher-altitude that are composed of glaciofluvial sandurs, deltas areas that are located above and between the sig- and ice-marginal (both glaciofluvial and diamictic nificant ice-flow areas (i.e. ice-lobe provinces) material) deposits. Timewise, the major ice lobes existed and the The main interlobate regions: dominant landscape-forming components of drum- Päijänne interlobate region (PIN) lins, megalineations, ice marginal deposits, eskers Southern Ostrobothnian interlobate region (SOIN) and hummocky moraines were built mainly during Middle Ostrobothnian interlobate region (MOIN) the latest phase of the last deglaciation, in the Late Ranua interlobate region (RIN) Weichselian, and the Early Holocene, c. 13 000 to 10 000 cal. BP (see Fig. 1). Less extensive interlobate regions in Lapland; located between areas where ice was still flowing Pre-Younger Dryas ice-lobe province relatively fast, the ice lobes of Kuusamo and Salla: Southern coastal Finland province (SCF) Pello interlobate region (PEIN) Sodankylä interlobate region (SODIN) The main glacial dynamic ice-lobe provinces can in Savukoski interlobate region (SAIN) some cases be divided into sub-provinces. There are also areas than have been overridden by ice flow of Fell regions in northernmost Lapland younger ice lobes. These sub-provinces and areas Kevo interlobate fell region (KEINF) constitute mappable geological entities. Kilpisjärvi interlobate fell region (KIINF)

The main ice-lobe provinces of the Younger Dryas Ice-divide zone Ice-divide zone (ID) and early Holocene Ice-divide zone corresponds to the central zone of Baltic Sea ice-lobe province (BSIL) the ice sheet characterized by exceptionally low ice- – Loimaa sub-province (BSIL-L) flow activity and low glacial erosion during the last Finnish Lake District ice-lobe province (FLDIL) glaciations; the area includes the remains of intense – FLDL sub-province (overridden by Näsijärvi– pre-glacial weathering (Hall et al. 2015, Nenonen Jyväskylä lobe ice flow) (FLDIL-OR) et al. 2018). A region in central Lapland located Oulu–North Karelian ice-lobe province (ONKIL) between the onset areas of ice lobes (Kuusamo, Kuusamo ice-lobe province (KIL) Inari, Enontekiö and Salla).

126 Geological Survey of Finland, Bulletin 412 Classification system of Superficial (Quaternary) Geological Units in Finland

4.2 Morpho-lithogenetic units (MLG units)

4.2.1 General natural sections and subsurface datasets such as borehole logs, excavation exposures, well records, The basic idea of the MLG approach is not new test pits and various geophysical interpretative data in Finland (see GTK superficial mapping guide; types (e.g. GPR, refraction and reflection seismics, Virkkala 1972). The combination of geomorpho- gravimetric profiling). logical, lithological (grain-size) and genetic aspects All MLG units are formed in an interpretative also formed an underlying context for the past 1:20 process. According to Lee & Booth (2006), “The 000 Quaternary mapping programme (1972–2007), combination of landform morphology, lithology but grain-size classes were still used as the main and formation process leads to interpreted morpho- descriptors for sediments, while geomorphol- lithogenetic units, which are mappable units that ogy was added for landform classification criteria. provide the basis for establishing a local stratigra- Currently, morpho-lithogenetic (MLG) classification phy.” The key components of the approach are the (e.g. McMillan 2005) is the principal method in the MLG map units defined by the interpreted genetic division of Quaternary map units at GTK. deposit type and the named MLG geological units High-resolution LiDAR DEM data bring out the characterized by a set of attributes. The combina- detailed geomorphology and landforms in the FIS tion of all MLG units will spatially provide full cov- area (e.g. Johnson et al. 2015, Ojala & Sarala 2017). erage in Finland. In recent years, the interpretation of these data The MLG interpretation may be complemented has become the main method in Quaternary map- by a lithostratigraphic approach. With sufficient ping (i.a. Sarala et al. 2015, Putkinen et al. 2017, data, the next step forward would be to incorpo- Sarala & Räisänen 2017). The MLG interpretation rate the local MLG model into the wider regional process allows a flexible combination, utilization stratigraphic context involving geochronology and and process flow for mapping and modelling, using lithostratigraphy (Figs. 4, 6). These elements con- different datasets such as previous maps (surface tribute to the evolution of the conceptual model lithology and deposit type), other mapping data and towards a completed map or 3D model. vertical sections deduced from temporary cuttings,

Fig. 6. Map units (top surface) classified by ‘genetic deposit type’ (blue text; see also Table 2) and their relationships with lithostratigraphic units (red text). All the underlined geological units (see Table 3) will be included in the FinstratiMP lexicon database.

127 Geological Survey of Finland, Bulletin 412 Jukka-Pekka Palmu, Antti E. K. Ojala, Joonas Virtasalo, Niko Putkinen, Jarmo Kohonen and Pertti Sarala

4.2.2 Morpho-lithogenetic map units; definition of genetic deposit type

Using the landform and lithology elements – process (the mode of origin) – may be interpreted. In practice, the MLG units are identified and formed in geological analysis based on the overall depositional context, landforms, existing mapping knowledge on lithology and, finally, on assumed depositional process (Fig. 7). The resulting map unit is classified according to the genetic deposit type, and the classification used at GTK is shown in Table 2. Obviously, the final step of the process, the definition of the genetic deposit type, is sensitive to the underpinning evolutionary model and to the presumed depositional environments as a part of the model. A well-established and communicated depositional context is a critical requirement for the attempted uniform ‘mapping result’. Glacial dynamic mapping with defined GD provinces and regions strongly supports the development of such a shared context. The current GTK system for genetic deposit types incorporates basinal fine sediment deposits in only one class (glaciolacustrine deposits and other basin fill deposits combined), beach deposits in only one class, and coarse fluvial deposits as one map-unit type (mainly in northern Finland). Organic deposits include peatlands but also other organic-rich sediments. Aeolian deposits are displayed in maps as dune crest polylines.

Fig. 7. The basic rationale for mapping Quaternary (superficial) deposits, showing the progression through landform and lithological observations to the interpretation of process and genesis. The MLG interpretation is complemented by the establishment of a local stratigraphy and finally utilized in the development of a regional 3D model (adopted from Lee & Booth 2006). Note that ‘morpho-lithogenetic unit’ in the diagram corresponds to the ‘morpho-lithogenetic map unit’ of this work.

128 Geological Survey of Finland, Bulletin 412 Classification system of Superficial (Quaternary) Geological Units in Finland

Table 2. Genetic deposit types used in GTK MLG map unit classification.

GTK classification Level 1 Level 2 Level 3

Glacigenic deposits, G Glacial deposits, GT Till, basal – includes lineations (drumlins etc.), GTb

Hummocky moraines (with various subtypes), GTh

Diamicton-dominated ice-marginal deposits, De Geer and other recessional moraines (also in groups of ridges) GTim

Glaciofluvial deposits, GF Eskers GFe

Ice-marginal glaciofluvial deposits (sandurs, deltas, subaqueous fan deposits), GFim

Other glaciofluvial deposits, (extramarginal, kames, kame and kettle) GFex

Basinal deposits, B Marine sediments BM Lacustrine sediments BL

Glaciolacustrine and -marine sediments, BG

Beach (littoral) Beach deposits on the higher hillslopes, deposits, L berms, bars, spits Beach deposits covering lower hillslopes and valleys

Fluvial deposits, F Coarse-grained fluvial depositsFc Deltas Fvd Fluvial deposits of variable grain size Fv

Aeolian deposits, E

Organic deposits Minerotrophic peatlands, fens PCt (peatlands), P Ombrotrophic peatlands, bogs PSt

Mass movement Mass movement deposits of fine-grained deposits M sediments Mass movement deposits produced by seismic activity Solifluction deposits Talus

Frost action deposits FR

Anthropogenic deposits A

4.2.3 Establishment of morpho-lithogenetic given by their characteristics using attributes and geological units classified according to the MLG type (see Table 3). Finally, the geological unit is named by combining The concluding step of the MLG process is the estab- the locality name with the MLG unit type. lishment of morpho-lithogenetic geological units. The key attribute of a MLG unit is the genetic The boundaries of the prominent geomorphological deposit type, which is directly reflected in MLG features/properties are relatively easy to identify, unit types (Table 3). The morpho-lithogenetic unit and the resulting geological units are locally mappa- types can also be seen as a subdivision or incre- ble entities based on landforms with an interpreted mental component of the genetic deposit types. (or inferred) depositional process. In most cases, In FinstratiMP, the characterization of a morpho- some supporting lithological information is avail- lithogenetic unit shall include the following features able to support the interpretation. The units are (i–iii) and corresponding attributes:

129 Geological Survey of Finland, Bulletin 412 Jukka-Pekka Palmu, Antti E. K. Ojala, Joonas Virtasalo, Niko Putkinen, Jarmo Kohonen and Pertti Sarala

Table 3. Morpho-lithogenetic unit types for FinstratiMP.

MLG geological unit type Genetic Main Typical Landform characteristics Deposit Lithology* Type Ice-marginal system GFim S, G, (D) An ice-marginal system of delta complexes and other related deposits, with delta plateaus, ice-marginal ridges >Delta complex GFim S, G, (D) Plateaus, often with the below-mentioned parts >>Delta (Sandur Delta) GFimd G, S, mS, fS Plateaus >>Sandur GFims G, S Plateaus, with meltwater channels >>Proximal ice contact zone unit GFimpic G, S, (D) See below, often overridden, kettle holes >>Ice-marginal ridge GFimpm G, S, (D) Ridge on top of the plateau (delineates the proximal part) >Ice-marginal ridge GFimr S, G, (D) A separate ridge Esker system GFe S, G The complete “train” >Esker GFeb S, G Esker main and linked branches >>Esker ridge GFer G, S Ridge, also a ridge delineated by kettle holes, with lateral depositional elements (see below) >>Esker sand (splay) GFes S (G) Esker lateral (and distal) depositional elements >>Esker delta GFed G, cS, mS, fS Delta component of an esker system (code GFimd) >>Kame area GFek S >Interlobate esker GFeil S, G Eskers at the boundaries of ice-lobe provinces and/or interlobate regions Other glaciofluvial deposit, GFex G, cS, mS, fS incl. extramarginal deposits Till system GTb D >Basal till GTbb D Veneer or blanket >Drumlin (lineation**) field GTblf D Lineation fields >>Drumlin/lineation** GTbl D Linear ridges (now polylines), normally not used as a unit Hummocky moraine GTh D Hummocky terrains and fields >Subglacial hummocky moraine GThb “ >>Ribbed moraines GThbr D, (S, G) “, Ribbed moraine geomorphology >>Murtoo moraines GThbm D, G, S “, Murtoo moraine geomorphology >Ice contact (passive, partly GThp D, S, (G) “ supraglacial) unit End moraines (diamicton-dominated) GTim D, (S) >End-moraine ridge (Reunamoreeni- GTimr D, (S) Ridge form, may be multiple combined muodostuma) (can be part of an ice-marginal ridges, mainly in conjunction with the ice delta complex) (Notice the material difference marginal systems compared to GFimr and GFimpm) >Recessional moraines, small ridges (field) GTimsr D, (S)

>>De Geer moraine field GTim- D (S) De Geer ridges in fields srDG >> Minor recessional moraine field GTimsrr D, (S) Usually supra-aquatic or shallow water deposition Dune field E fS Dune ridge field

* GEO classification, in English, typical examples: S = Sand, fS = Fine sand, mS = medium sand, cS = coarse Sand, G = Gravel, D = Diamicton, ** For drumlin/lineation: See text

130 Geological Survey of Finland, Bulletin 412 Classification system of Superficial (Quaternary) Geological Units in Finland

(i) Landform (morphology, geomorphology) • Kalvola-Renko Hummocky Moraine Field (Observed) – Karhulammi-Tähilammi Hummocky Moraine (ii) Genetic deposit type (Interpreted) (iii) Lithology (material of the deposit) (Observed 4.2.4 Major MLG units in Finland / Interpreted / Inferred / Not known) The number of attributes has not been limited The major MLG units are: to these, but additional features and descriptions, • Large glaciofluvial systems (Fig. 8), which con- such as age, stratigraphy or lithofacies (Miall 1985), sist of: or the more detailed depositional environment or – Large ice-marginal deposit systems (”forma- process, may be included. Key references to original tions”), also called end-moraine systems (of research papers are important. mainly sorted glaciofluvial material) It is pointed out that morpho-lithogenetic geo- – Large interlobate deposits (esker systems) logical units are currently only used for the gla- – Major ice-lobe provinces (intralobate) esker ciofluvial and moraine deposit types, which have systems distinctive positive geomorphological form. It • Large moraine fields, which consist of: is suggested that the definition and naming of – Hummocky moraine terrains (Fig. 2 in units (and their storage in FinstratiMP) would be Appendix 2) restricted to prominent, well-known and studied – Recessional (De Geer) moraine fields cases; the establishment of a new geological unit • Large drumlin fields, which are also related to is only appropriate in cases where it substantially the main till deposit units (Fig. 2 in Appendix 2) aids in the overall data usefulness. It is noted that the map features corresponding Morpho-lithogenetic units have a hierarchy to MLG units can be either a polygons or polylines. ranging from smaller into larger, from depositional For example, the Pieksämäki drumlin field, and the complexes to systems (Figs. 9, 10, 11). For example, corresponding information in FinstratiMP, may Vesivehmaankangas sandur delta (Fig. 10), a com- refer to all the drumlins of the Pieksämäki region plex consisting of sandur, delta, proximal ice-con- mapped as polygons or polylines if these symbolize tact parts and a push moraine ridge element, form the drumlins. However, if the drumlin polylines are a deposit complex in the system of ice-marginal lineations indicating the transposition (reorienta- deposits of the Second Salpausselkä of the Finnish tion) structure of the sedimentary material, it must Lake District ice-lobe province. Likewise, a major be conceptually classified as a geological structure esker forms a system whose elements are the esker (not a geological unit) and attributed accordingly. ridges, adjoining glaciofluvial sediment depos- The FinstratiMP MLG unit name is formed by the its and, if practical, esker deltas have also been combination of the locality name (e.g. ‘Pielisjärvi’) delineated (Fig. 11). or landform name (e.g. ‘Salpausselkä’) with the unit Similarly, esker systems and hummocky moraine type given in Table 3. Here are some examples: areas in the central area of the Finnish Lake District • Second Salpausselkä (FLDIL part) Ice-marginal ice-lobe province (FLDIL) are shown in Figure 11. System The esker systems consist of the morpho-litho- – Vesivehmaankangas Delta Complex genetically mapped smaller areas (the ridges, • Pielisjärvi Ice-marginal System sometimes esker deltas, and adjacent areas of gla- • Hämeenkoski-Kangasala-Pyynikki-Ylöjärvi ciofluvial deposition). In Figure 11, the various types Esker System of glacial lineations (e.g. drumlins, megaflutings, • Asikkala-Joutsa Esker System flutings) are also shown, as are • Pieksämäki Drumlin Field – Paltamäki Drumlin

131 Geological Survey of Finland, Bulletin 412 Jukka-Pekka Palmu, Antti E. K. Ojala, Joonas Virtasalo, Niko Putkinen, Jarmo Kohonen and Pertti Sarala

Fig. 8. Examples of significant glaciofluvial morpho-lithogenetic units in Finland: ice-marginal systems, major interlobate and intralobate esker systems. E.M = end moraine, aka ice marginal systems; names along the grey lines correspond to major esker systems e.g- Joroinen-Kerimäki-Punkaharju. Basemap © National Land Survey of Finland.

132 Geological Survey of Finland, Bulletin 412 Classification system of Superficial (Quaternary) Geological Units in Finland

Fig. 9. Morpho-lithogenetic units of the southern part of the Finnish Lake District ice-lobe province. On the map are shown the glaciofluvial deposits (eskers and Salpausselkä ice-marginal deposits (also referred as end moraines) (sandurdelta/delta complexes, green; also diamiction-dominated ridges, dark brown)) and various types of hummocky moraines and other glacial deposits (browns). The two Salpausselkä ice-marginal systems, with their ice-marginal sandur deltas, form distinct and fairly continuous chains across the map area, from the Lahti region in the west to Imatra in the east. Esker systems radiate from the ice-marginal deposit (also called end moraine) zone towards the north. Hummocky moraines form regions and discontinuous chains. Basemap © National Land Survey of Finland.

133 Geological Survey of Finland, Bulletin 412 Jukka-Pekka Palmu, Antti E. K. Ojala, Joonas Virtasalo, Niko Putkinen, Jarmo Kohonen and Pertti Sarala

Fig. 10. Vesivehmaankangas delta complex and its surroundings. The mapping classification includes also covering diamicton in the proximal part of the complex. Basemap and LiDAR data © National Land Survey of Finland.

Fig. 11. Pieksämäki area in the central area of the Finnish Lake District ice-lobe province. Esker systems are shown with green, hummocky moraine fields with light brown and glacial lineations with purples. Blue areas are lakes. Basemap and LiDAR data © National Land Survey of Finland.

134 Geological Survey of Finland, Bulletin 412 Classification system of Superficial (Quaternary) Geological Units in Finland

4.3 Lithostratigraphic units

4.3.1 General adequately vertical log and profile data on representative superficial deposits. Type section localities A lithostratigraphic unit consists of an organization (observations points) include natural escarpments of rock strata, which are defined and distinguished (e.g. erosional riverbanks) and, more typically, man- on the basis of their lithological characteristics. made excavations such as quarries, roadside sec- Lithostratigraphic units are defined independently tions and geological test pits. Morpho-lithogenetic of the inferred geological history, mode of genesis units can be complemented by lithostratigraphic or biological development. A formation is the fun- units (formation, member, bed) only after the type damental unit (Fig. 12), defined as a type section section (stratotype) has been described and named. (stratotype). A formation shall have lateral conti- Formal stratigraphic description may not be the nuity, but it is not tied to age, so it can occur as a most suitable method to report investigations in diachronic unit. Lithostratigraphic units should be most applied (e.g. groundwater, engineering) and defined by practical purpose, and for terminological research projects. However, when combined with stability, a type locality should always be presented. facies analysis, the definition of architectural ele- For the procedures related to lithostratigraphy, ments (e.g. Miall 1985), the stratotypes will provide Salvador (1994) and McMillan et al. (2011) are a valuable addition to the national information base. referred to. Well defined, and formally documented lithostrati- The challenges of a standard lithostratigraphic graphic units form a cumulative, uniform, observa- method with glacial deposits were discussed in tion-based dataset and one fundamental foundation Chapter 3.1. In Finland, Quaternary lithostrati- of geological information in Finland. graphic units (LS) have been defined when there is

Lithology: Structured description of rocks (both consolidated and unconsolidated) on the basis of such characteristics as colour, mineral composition, grain size, texture and structures (cf. GoG 2005).

UPPER RANKS: • Supergroup: A supergroup may be used for several associated groups or associated formations and groups with significant lithological properties in common. • Group: A group is the formal lithostratigraphic unit next in rank above a formation and is commonly applied to a sequence of contiguous formations with significant diagnostic lithological characteristics. • Subgroup: A group may be divided into subgroups, although it is not in the formal hierarchy but has been usefully employed for subdividing certain groups.

PRIMARY UNIT: • Formation: A formation is the primary formal unit of lithostratigraphic classification used to map, describe and interpret the geology of a region. A formation is generally defined as the smallest mappable unit and has lithological characteristics that distinguish in from adjacent formations. However, component members and beds may be mappable in maps and 3D models, depending on the resolution. A formation is defined by a type section (stratotype) or type area.

LOWER RANKS: • Member: A member is the formal lithostratigraphic unit next in rank below a formation and is always part of a formation. Formations need not to be divided either wholly or partially into members. Member may extend from one formation to another. • Bed: A bed is the smallest formal unit in the hierarchy of sediment lithostratigraphic units. Bed names are commonly applied to distinctive units that may be thin and laterally restricted or known only from a borehole or single exposure. Some beds may be fossiliferous or yield dateable material (e.g. a soil, peat or bone bed). A bed status tends to be assigned for units with some palaeogeographical, geochronological or specific lithological significance.

Fig. 12. Summary of the key concepts and terms of lithostratigraphic classification (Salvador 1994, McMillan et al. 2011).

135 Geological Survey of Finland, Bulletin 412 Jukka-Pekka Palmu, Antti E. K. Ojala, Joonas Virtasalo, Niko Putkinen, Jarmo Kohonen and Pertti Sarala

4.3.2 Lithostratigraphic units in Finland Representative examples of lithostratigraphic studies in Finland include (Fig. 13): The number of formally defined lithostratigraphic • Bouchard et al. (1990); Kela Formation (western units of Finnish superficial sediments is relatively Uusimaa); Members: Espoo Till, Pickala Sands and low. The use of sedimentological techniques and Siuntio Till. facies analysis to study superficial sediment sec- • Nenonen (1995) described several Pleistocene till tions during the past 30 years have increased has stratigraphies from eastern, southern and west- generated a number of site-specific studies with ern Finland; Sallila (Vampula) and Horonkylä detailed section descriptions. Formations, members (Teuva) till stratigraphy. and beds that have been described according to the • Pitkäranta (2005, 2013) and Pitkäranta et al. principles of formal lithostratigraphic classification (2014): formal lithostratigraphy of the Suupohja (e.g. Bouchard et al. 1990, Pitkäranta et al. 2014, region in western Finland (Ostrobothnia). Salonen et al. 2014, Lunkka et al. 2015). In addition, • Salonen et al. (2008), Salonen et al. (2014) and numerous precise descriptions of sediment vertical Lunkka et al. (2015): lithostratigraphy of Hitura, sections are available (e.g. Hirvas & Nenonen 1987, Hannukainen and Rautuvaara in northern Hirvas 1991, Sutinen 1992, Nenonen 1995, Sarala Ostrobothnia and western Lapland. 2005, Sarala et al. 2016, Ojala et al. 2018a, Putkinen • Sarala (2005) Peräpohjola lithostratigraphy et al. 2020), which can be considered and classified (Table 4) with type sections. as lithostratigraphic units. The current state of the Quaternary lithostratigraphic units can be found in FinstratMP.

Table 4. An example of lithostratigraphic unit division from the Peräpohja area (from Sarala 2005).

The interglacial and interstadial deposits are sions of the Saalian, Eemian, Weichselian and some important marker horizons in studies on glacial Weichselian interstadial stages. The data collected history in Finland. Tornivaara & Salonen (2007) (STRATO final report; Tornivaara & Salonen 2007) collected and systematically classified (STRATO enable the definition of lithostratigraphic units database) a large number of investigations that based on regional type sections. Pre-Weichselian present stratigraphic units from continuous succes- geological (lithostratigraphical) units, typically

136 Geological Survey of Finland, Bulletin 412 Classification system of Superficial (Quaternary) Geological Units in Finland covered by Weichselian and post-Weichselian sedi- (Putkinen et al. 2020) in Lapland, Vesiperä in ments, have been described in examples from Sokli Middle Ostrobothnia (Nenonen 1995), Harrinkangas in eastern Lapland (Helmens et al. 2015, Kylander (Gibbard et al. 1989, Räsänen et al. 2015), Hitura et al. 2017), the Suupohja region in Ostrobothnia (Salonen et al. 2008) and Mertuanoja (Eriksson et (Pitkäranta et al. 2014), Tepsankumpu, Kittilä al. 1999, Nenonen 1995). (Saarnisto et al. 1999), and Äältövittikot, Sodankylä

Fig. 13. Key locations of the stratigraphic record of superficial deposits in Finland. Locations: Kela and Lommila (Bouchard et al. 1990); Vuosaari (Hirvas et al. 1995); Sallila, Horonkylä, Haapalankangas, Eteläkylä, Kaasila, Pampalo, Ruotanen, Vesiperä, Mertuanoja, Vuojalankangas (Nenonen 1995); Risåsen, Penttilänkangas, Karhukangas, Harrinkangas (Pitkäranta 2013); Hitura (Salonen et al. 2008); Ruunaa (Lunkka et al. 2008); Vammavaara, Petäjävaara, Sihtuuna, Korttelivaara, (Sarala 2005); Saarenkylä (Sutinen 1992); Rautuvaara (Lunkka et al. 2015); Hannukainen (Salonen et al. 2014); Sokli (Helmens et al. 2015); Koivusaarenneva (Lunkka et al. 2016); Kaarreoja (Sarala et al. 2016) and Äältövittikot (Putkinen et al. 2020). Basemap data © National Land Survey of Finland.

137 Geological Survey of Finland, Bulletin 412 Jukka-Pekka Palmu, Antti E. K. Ojala, Joonas Virtasalo, Niko Putkinen, Jarmo Kohonen and Pertti Sarala

4.4 Allostratigraphic units

4.4.1 General minology has, in practice, replaced the convention suggested by the IUGS Guide (Salvador 1994). The International Stratigraphic Guide (Salvador An allostratigraphic unit is a mappable body of 1994) recognizes a classification category based rock that is defined and identified on the basis of its on stratal discontinuities (unconformity-bounded bounding discontinuities (NACSN 2005). The fun- unit), but the corresponding unit type, synthem, has damental unit is an alloformation with a lower rank not been widely used. In many countries (including of allomember and a higher rank of allogroup. For Finland; Virtasalo et al. 2005, 2007, 2014), a simi- terminology, procedures and examples of formal lar system of allostratigraphic classification (North allostratigraphy, the North American Stratigraphic American Stratigraphic Code, NACSN 2005) and ter- Code (NACSN 2005) is referred to.

Fig. 14. (A) Seismoacoustic sub-bottom profile (12 kHz pinger) and allostratigraphic units from the Archipelago Sea. (B) Corresponding Wheeler diagram with time on the vertical axis. Modified from Virtasalo et al. (2007). Stratigraphic units after Virtasalo et al. (2010).

138 Geological Survey of Finland, Bulletin 412 Classification system of Superficial (Quaternary) Geological Units in Finland

It is emphasized that the system is fundamentally Allostratigraphic units are the preferred means of based on bounding surfaces (discontinuities, uncon- stratigraphic classification instead of conventional formities) between the units – not on the lithology practice of classifying sediments according to the or other properties of the units themselves. Many so-called Baltic Sea Stages (Baltic Ice Lake, Yoldia of the discontinuities originally represent either Sea, Ancylus Lake, Littorina Sea, etc.). Conventional erosional surfaces or periods of non-deposition practice lacks clear and consistent definitions and (‘hiatus’) (see Virtasalo 2017). Based on their obser- are incompatible with international stratigraphic vation that substantial lithological heterogeneity approaches (cf. Virtasalo et al. 2014, Virtasalo 2017). typically complicates the lithostratigraphic clas- Even though the classification principles of sification of glacial deposits, Räsänen et al. (2009) lithostratigraphy and allostratigraphy differ, in proposed a procedure involving the combined use of practice they are based on the same informa- allostratigraphy and lithostratigraphy (CUAL) as a tion: the visual characteristics of sediment units. classification basis for (Quaternary) glacial deposits. Therefore, Räsänen et al. (2009) developed a combined allo- and lithostratigraphic approach (CUAL) 4.4.2 Allostratigraphic units in Finland where sediments are classified on the basis of significant unconformities into allostratigraphic units, Allostratigraphy has proven particularly useful which can be further subdivided into lithostrati- in marine geological surveys, where significant graphic units by lithological criteria. Virtasalo et unconformities can readily be identified and traced al. (2005, 2007, 2010) used the CUAL approach for over distances in high-resolution seismoacoustic subdividing late- and postglacial sediments in the sub-bottom profiles that are routinely collected Archipelago Sea into Dragsfjärd, Korppoo and Nauvo (Virtasalo et al. 2005, 2007, 2010, 2014). For exam- Alloformations, and the Korppoo Alloformation fur- ple, the base of the brackish-water mud is traceable ther into the lithostratigraphic Trollskär and Sandön in sub-bottom profiles over the whole Baltic Sea Formations (Fig. 14). In the neighbouring sea area, (Virtasalo et al. 2016). Allostratigraphic units iden- Virtasalo et al. (2014) subdivided brackish-water tified in offshore seismoacoustic profiles can be cor- muds corresponding to the Nauvo Alloformation related with those on land on the basis of significant into local allomembers. All the defined allostrati- unconformities identified, for example, by ground- graphic units will be stored in the FinstratiMP penetrating radar surveys and electrical resistivity database. tomography (Ojala et al. 2018b, Virtasalo et al. 2019).

5 SUMMARY AND IMPLICATIONS

As a national Geological Survey, GTK maintains, damentally important. The use of MLGs has been gathers, refines and distributes geological data in described by Lee and Booth (2006, p. 21) as (edited): Finland. The definition and development of national “…geological interpretations of morphological fea- procedures, the geological unit framework, map tures will be based upon geological hypotheses devel- compilations and maintenance of the geological oped by the geologist for an individual mapping area. It unit database (digital Lexicon) are essential com- is critical therefore that these hypotheses and geologi- ponents of these activities. This document defines cal interpretations can evolve and are testable based these issues from the viewpoints of geological unit upon field observations. As a consequence of this need description and map data management. for testing and re-evaluation, pure morphological map- Lithostratigraphy and allostratigraphy are well ping is perhaps best suited to areas where the relief and established classification systems with defined geology is not complex – for instance lowland areas. terms and procedures (Salvador 1994, McMillan Geomorphological mapping enhances the purely mor- et al. 2011). In this work the main emphasis has phological approach, as it also involves determining the been to define and explain the use of the morpho- genesis of the observed landforms, taking into account lithogenetic (MLG) units. The use of MLG units in lithologies and their spatial geometry (including stra- LiDAR DEM-based mapping and classification of tigraphy). As sound interpretation is the key to the suc- Quaternary superficial deposits in Finland is fun- cess of this method, it requires a good understanding of

139 Geological Survey of Finland, Bulletin 412 Jukka-Pekka Palmu, Antti E. K. Ojala, Joonas Virtasalo, Niko Putkinen, Jarmo Kohonen and Pertti Sarala landform assemblages and their genesis, together with of glacial dynamical activity during the latest an appreciation of other appropriate field and laboratory Weichselian deglaciation. However, we note that the techniques that might assist in interpretation. Whatever time-dependent dynamic evolution of the ice sheet other methods are brought into the geomorphological resulted in overlapping glacial dynamic characteris- survey (e.g. if remotely sensed data are available, they tics, which are not yet included in the GD unit divi- can serve to increase the rate of ground coverage and sion. They will be supplemented later based on the reduce field time), groundtruthing remains an essential available fragmentary information on the various element (e.g. to confirm remotely sensed interpretations, ice-flow systems and ice-marginal deposits. This to observe sections and to record lithologies).” information has for the most part been discovered It is noted, however, that morpho-lithogenetic from interlobate GD regions of the last deglacia- classification does not achieve the accuracy and for- tion and the ice-divide zone, but partly also from mality of the traditional schemes of stratigraphic the ice-lobe GD provinces, especially the Kuusamo classification (Salvador 1994). Furthermore, both ice-lobe province of the last deglaciation (Sutinen the fundamental definition of MLG units and the 1992, Kleman et al. 1997, Lunkka et al. 2004, Sarala interpretation process leading to the actual MLG 2005, Johansson et al. 2011). map units can easily be criticized as ‘inexplicit’ or The renewed LiDAR DEM-based interpretation ‘ambiguous’. The definition and mapping of MLG process is complemented at GTK by the develop- units is obviously dependent on the experience and ment of modelling (2.5D and 3D) activities (cf. the ‘mind set’ of the interpreting person – to some Ojala et al. 2018a, Kohonen et al. 2019). MLG units degree, at least. constitute a Quaternary 2D-map theme. MLG units Experiences gained in the regional LiDAR-based and lithological units with defined boundaries (sur- mapping of glacial deposits in Finland have proven faces), together with (depositional) architectural the usefulness of the informal MLG approach as elements, are the main constituents of a regional a frame for practical map data production (e.g. 3D framework. At a detailed scale, the recognition Putkinen et al. 2017). The mapped MLG units also and application of architectural elements, packages provide a framework and a starting point for both of genetically related strata recording aggradation the lithostratigraphy and Quaternary 3D geology. during the successive depositional events, are of Glacial sediments have been mapped in Finland with growing importance. Architectural elements can the morpho-lithogenetic deposit approach using a therefore be regarded as the basic building blocks classification of glacigenic and glaciofluvial deposit of any (stratigraphic) succession, and their man- types. The MLG system is an important part of the agement as geological units needs to be resolved. larger system, as the glacial dynamic provinces and Geological maps, 3D models and map features, regions are largely based on the spatial distribution such as glacial dynamic regions or MLG units, are and characteristics of the MLG units; as an exam- interpretations, and interpretations are vulnerable ple, the ice-marginal systems and other first-order to changes. In contrast, well-defined stratigraphic datasets, such as drumlin fields and esker systems, units are based on observation at a documented site, together form a glacial dynamic province when and stratigraphic units form a cumulative foun- combined. Subdivision of the deposits into their dation of geological information. FinstratiMP will textural, morphological and genetic components is be the digital national lexicon for all the defined theoretically possible but seldom practically pos- Quaternary units in Finland. Due to the lack of a sible (Fulton 1993, McMillan & Powell 1999). comprehensive chronostratigraphic scheme, the The glacial dynamic provinces and regions cor- depositional age (determined or inferred) will be respond to the past ice (stream) lobe provinces and included in FinstratiMP as a unit attribute, when the interlobate regions. Thus, the map unit term possible and appropriate. ‘ice lobe’ (e.g. Finnish Lake District ice lobe) used The residual units (palaeosols of unknown age) by Putkinen et al. (2017) has been replaced by the are to be included in the FinstratiKP (digital lexicon term ‘ice-lobe province’ – the current region and for the bedrock units) together with sporadic pre- map unit corresponding to the palaeoterm ‘ice lobe’. Quaternary sedimentary units (e.g. some marine The concept of glacial dynamic provinces has clays, diatomites) and unmetamorphic sedimentary now been applied to deposits corresponding to a rocks of Finland. relatively short, albeit the most important stage

140 Geological Survey of Finland, Bulletin 412 Classification system of Superficial (Quaternary) Geological Units in Finland

ACKNOWLEDGEMENTS

We are grateful to Gustaf Peterson Becher and script and reconsider some terminological issues. Juha Pekka Lunkka for their firm and constructive Tapio Väänänen made suggestions for the early ver reviews, which helped us to consolidate the manu sion, and Viena Arvola assisted with the figures.

LIST OF APPENDICES

Appendix 1 Glacial dynamic (GD) provinces and regions (map units) in Finland: definition, identification, characterization and description

Appendix 2 Morpho-Lithogenetic (MLG) geological units in Finland: identification and characterization

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Pitkäranta, R. 2005. A proposal for formal lithostrati- Sarala, P. & Räisänen, J. 2017. Evolution of the eastern graphical names in the Suupohja region, western Fin- part of Kuusamo Ice lobe based on geomorphological land. In: Ojala, A. E. K. (ed.) Quaternary studies in the interpretation of high-resolution LiDAR data. Bulle- northern and Arctic regions in Finland: Proceedings of tin of the Geological Society of Finland 89:2, 82–99. the workshop organized within the Finnish National doi:10.17741/bgsf/89.2.002 Committee for Quaternary Research (INQUA) Kilpis- Sarala, P., Räisänen, J., Johansson, P. & Eskola, K. O. 2015. järvi Biological Station, Finland, January 13–14th Aerial LiDAR analysis in geomorphological mapping 2005. Geological Survey of Finland, Special Paper 40, and geochronological determination of surficial -de 91–95. Available at: http://tupa.gtk.fi/julkaisu/spe- posits in the Sodankylä region, northern Finland. GFF cialpaper/sp_040_pages_091_095.pdf 137:4, 293–303. Pitkäranta, R. 2013. Lithostratigraphy and age of pre-late Sarala, P., Väliranta, M., Eskola, T. & Vaikutiné, G. 2016. Weichselian sediments in the Suupohja area, West- First physical evidence for forested environment in ern Finland. PhD thesis, University of Turku. Annales the Arctic during MIS 3. Scientific Reports 1, 6:29054. Universitatis Turkuensis A II 284. 66 p. Available at: https://10.1038/srep29054 Pitkäranta, R., Lunkka, J.-P. & Eskola, K. O. 2014. Schenk, H. G. & Muller, S. W. 1941. Stratigraphic termi- Lithostratigraphy and Optically Stimulated Lumines- nology. Bull. Geol. Soc. Am., 52, 1419–1426. cence age determinations of pre-Late Weichselian Stroeven, A. P., Hättestrand, C., Kleman, J., Heyman, J., deposits in the Suupohja area, western Finland. Bo- Fabel, D., Fredin, O., Goodfellow, B. W., Harbor, J. M., reas 43, 193–207. Jansen, J. D., Olsen, L., Caffee, M. W., Fink, D., Lund- Punkari, M. 1980. The ice lobes of the Scandinavian ice qvist, J., Rosqvist, G. C., Strömberg, B. & Jansson, K. sheet during the deglaciation of Finland. Boreas 9, N. 2016. Deglaciation of Fennoscandia. Quaternary 307–310. Science Reviews 147, 91–121. Available at: http:// Punkari, M. 1997. Glacial and glaciofluvial deposits in the dx.doi.org/10.1016/j.quascirev.2015.09.016 interlobate areas of the Scandianavian ice sheet. Qua- Sutinen, R. 1992. Glacial deposits, their electrical prop- ternary Science Reviews 16, 741–753. erties and surveying by image interpretation and Putkinen, N., Eyles, N., Putkinen, S., Ojala, A. E. K., Pal- ground penetrating radar. Geological Survey of Fin- mu, J.-P., Sarala, P., Väänänen, T., Räisänen, J., Saa- land, Bulletin 359. 123 p. Available at: https://tupa.gtk. relainen, J., Ahtonen, N., Rönty, H., Kiiskinen, A., fi/julkaisu/bulletin/bt_359.pdf Rauhaniemi, T. & Tervo, T. 2017. High-resolution Li- Tornivaara, A. & Salonen, V.-P. 2007. Maaperän kerro- DAR mapping of ice stream lobes in Finland: Bulletin sjärjestyksen monimuotoisuus ja suojelu. STRATO- of the Geological Society of Finland 89, 64–81. projektin loppuraportti, Helsingin yliopisto, Geolo- Putkinen, N., Sarala, P., Eyles, N., Pihlaja, J., Daxber- gian laitos. 73 p. ger, H. & Murray, A. 2020. Reworked Middle Pleis- Virkkala, K. 1972. Maaperäkartoituksen maasto-opas. tocene deposits preserved in the core region of the Geologinen tutkimuslaitos, Opas N:o 4. 38 p. Available Fennoscandian Ice Sheet. Quaternary Science Ad- at: https://tupa.gtk.fi/julkaisu/opas/op_004.pdf vances, 100005. Available at: https://doi.org/10.1016/j. Virtasalo, J. J. 2017. Kerrostunut ja puuttuva aika. Geologi qsa.2020.100005 69, 98–106. Räsänen, M. E., Auri, J., Huitti, J., Klap, A. & Virtasalo, Virtasalo, J. J., Endler, M., Moros, M., Jokinen, S. A., Hä- J. J. 2009. A shift from lithostratigraphic to allostrati- mäläinen, J. & Kotilainen, A. T. 2016. Base of brack- graphic classification of Quaternary glacial deposits. ish-water mud as key regional stratigraphic marker of GSA Today 19 (2), 4–11.

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mid-Holocene marine flooding of the Baltic Sea Basin. mation in the Archipelago Sea, northern Baltic Sea. Geo-Marine Letters 36, 445–456. Bulletin of the Geological Society of Finland 82, Virtasalo, J. J., Hämäläinen, J. & Kotilainen, A. T. 2014. 63–68. Toward a standard stratigraphical classification prac- Virtasalo, J. J., Kotilainen, A. T., Räsänen, M. E. & Ojala, tice for the Baltic Sea sediments: the CUAL approach. A. E. K. 2007. Late-glacial and post-glacial deposition Boreas 43, 924–938. in a large, low relief, epicontinental basin: the north- Virtasalo, J. J., Kotilainen, A. T. & Räsänen, M. E. 2005. ern Baltic Sea. Sedimentology 54, 1323–1344. Holocene stratigraphy of the Archipelago Sea, north- Virtasalo, J. J., Schröder, J. F., Luoma, S., Majaniemi, J., ern Baltic Sea: the definitions and descriptions of the Mursu, J. & Scholten, J. 2019. Submarine groundwater Dragsfjärd, Korppoo and Nauvo Alloformations. Bal- discharge site in the First Salpausselkä ice-marginal tica 18, 83–97. formation, south Finland. Solid Earth 10, 405–423. Virtasalo, J. J., Kotilainen, A. T. & Räsänen, M. E. 2010. Definitions of Trollskär Formation and Sandön For-

144 Geological Survey of Finland, Bulletin 412 Classification system of Superficial (Quaternary) Geological Units in Finland

APPENDIX 1

15.4.2021

GLACIAL DYNAMIC (GD) PROVINCES AND REGIONS (MAP UNITS) IN FINLAND: DEFINITION, IDENTIFICATION, CHARACTERIZATION AND DESCRIPTION

J.-P. Palmu, A. E. K. Ojala, J. Virtasalo, N. Putkinen, J. Kohonen & P. Sarala

CONTENTS

1 GD PROVINCE AND REGION IDENTIFICATION...... 146

2 GD PROVINCE BOUNDARY DEFINITION AND BOUNDARY TYPE CLASSIFICATION...... 146 2.1 Outer margins ...... 146 2.2 Lateral margins of the GD provinces ...... 146 2.3 Inner margins of the GD provinces...... 147

3 GLACIAL DYNAMIC PROVINCE/REGION GEOLOGICAL MAP UNIT ATTRIBUTES ...... 148

4 GD PROVINCE AND REGION CHARACTERIZATION...... 148

REFERENCES...... 151

145 Geological Survey of Finland, Bulletin 412 Jukka-Pekka Palmu, Antti E. K. Ojala, Joonas Virtasalo, Niko Putkinen, Jarmo Kohonen and Pertti Sarala

1 GD PROVINCE AND REGION IDENTIFICATION

Glacial dynamic provinces and regions are identi- tute a continuum and form an independent flow set fied and defined by their ice-flow characteristics system for each glacial dynamic ice-flow province. or lack of them in terrain surface morphology. In addition, other morpho-lithogenetic units and The ice-flow intensity is indicated by the lineation landforms, such as glaciofluvial eskers and fields length and axial dimensions of the various types of hummocky moraines, are used in the identifica- of drumlins, mega-scale lineations, crag and tails, tion and delineation of glacial dynamic provinces etc. The ice-flow direction indicators, such as line- and regions ations and other flow-indicating features, consti-

2 GD PROVINCE BOUNDARY DEFINITION AND BOUNDARY TYPE CLASSIFICATION 2.1 Outer margins

Ice-lobe GD provinces have outer margins that Hämeenkangas is the Baltic Sea ice-lobe GD constitute ice-marginal deposit (also called end province. moraine) zones (see Figs. 8 and 9 in the main d. For many ice-lobe GD provinces in Finland, the article). outer margins are ice-marginal positions, often a. Salpausselkä ice-marginal deposits of the Finnish ice-marginal glaciofluvial deposit zones out- Lake District ice-lobe province (FLDIL) and the side Finland, in Russia and Norway. In Norway, Baltic Sea ice-lobe province (BSIL). the Younger Dryas stage ice-marginal positions b. In Northern Karelia, for the Oulu–Northern are in northernmost Norway for the Inari and Karelia ice-lobe (ONKIL) glacial dynamic prov- Enontekiö ice-lobe provinces. In Russia, ice- ince, ice-marginal glaciofluvial deposits and marginal positions are in northwestern Russia diamicton-dominated ice-marginal ridges corre- for most of the Oulu–Northern Karelia ice-lobe sponding to the Salpausselkäs are, from southeast GD province and for the whole of the Kuusamo to northwest: the Värtsilä–Tohmajärvi ice- ice-lobe province. marginal system, continuing northeast towards e. The southern coastal Finland GD province (SCF) Tuupovaara, the Kiihtelysvaara ice-marginal (south/southeast of the Salpausselkäs and system, which continues northeast, south of Lake Northern Karelian ice-marginal deposit zone). Koitere, and the Pielisjärvi ice-marginal system, The outer (distal) boundary of this province is which continues northeast, north of Patvinsuo outside Finland, towards the south and southeast national park. in Estonia and Russia. GD province ice flow was c. For the Näsijärvi–Jyväskylä ice-lobe (NJIL) towards the Pandivere–Neva ice-marginal posi- GD province, the Central Finland ice-marginal tion (Donner 1995). The glacial geological devel- deposit zone is its outer margin. Towards the opment of this province dates from an earlier west is Hämeenkangas, which is also an inter- period (before 13 cal. ka) compared to the other lobate deposit, and on the southern side of glacial dynamic provinces.

2.2 Lateral margins of the GD provinces

Lateral margins of the GD provinces are variable area, an interlobate deposit was formed, as in and can be characterized as follows: the final stage the ONKIL GD province prevailed, f. The margins between ice-flow lobes have been but at an earlier stage, FLDIL GD province ice dynamic zones, with changes in flow intensity flow was dominant further northeast of the later- and direction. In some cases, one ice-flow sys- formed interlobate deposit. A similar develop- tem (lobe) has finally prevailed over the adjacent ment occurred in the Jyväskylä region, where the flow system. An example of this is the border Näsijärvi–Jyväskylä ice-lobe (NJIL) GD province between the Oulu–Northern Karelia ice-lobe area now overlaps the ice-flow system of the province (ONKIL) and the Finnish Lake District FLDIL GD province area, as the NJIL ice margin ice-lobe province (FLDIL) at Outokumpu. In that readvanced east- and southeastwards.

146 Geological Survey of Finland, Bulletin 412 Classification system of Superficial (Quaternary) Geological Units in Finland g. Some of the margins between GD provinces are h. Indistinct lateral borders are typical for GD gradational and/or diffused. There is often, but provinces and regions of Northern Finland. An not always, an interlobate deposit: a smaller example of this is the Pello interlobate GD region, interlobate glaciofluvial “esker” or a large inter- located between the flow sectors of the Kuusamo lobate formation between the ice-lobe provinces ice-lobe GD province. The southern margin of the and the interlobate regions. The latter clearly Kuusamo ice-lobe GD province is also indefinite separates provinces and regions of distinct gla- and indistinct, and to a large extent can only be cial dynamic activity. An example of interlobate inferred from the flow indications. In Northern deposits is the system of deposits running from Finland, confusion is also caused by indications Hossa via Taivalkoski in the east towards the west of ice-flow systems of earlier (pre-Last Glacial via Pudasjärvi and further on to the shores of the Maximum, LGM) glacial stages. For example, in northern Bothnian Bay. The system of depos- the Ranua interlobate GD region, in the Kemi– its delineates the boundary between the Oulu– Tornio area, there is a drumlin field of presum- Northern Karelia ice-lobe (ONKIL) GD province ably the Middle Weichselian stage. and the Ranua interlobate (RIL) GD region.

2.3 Inner margins of the GD provinces

GD ice-lobe provinces mostly have inner margins Näsijärvi–Jyväskylä (NJIL), the onset zones are in that are onset zones of their ice-flow systems. the sea areas west of Finland, in the Bothnian Bay. For the GD ice-lobe provinces of the Baltic Sea For the Kuusamo, Salla, Inari and Enontekiö ice- (BSIL), the Finnish Lake District (FLDIL), Oulu– flow areas (lobes), the onset zones are diffuse areas Northern Karelia (ONKIL) and the relatively younger towards the ice-divide zone.

Table 1. Generic descriptions for the boundaries within the glacial dynamic province (GDP) classification in Finland.

UNIT Boundary type Boundary type Boundary type Boundarytype Boundary type BOUNDARY; (Geological Relation) (Geological (Geological (Geological (Geological MAIN Glacial dynamic Relation) Relation) Relation) Relation) DESCRIPTORS (Descriptive Deposit (D) Bed (B) Spatial Spatial Spatial

GLACIAL DYNAMIC CLASS / RANK Nature Contact Location Nature Width Glacial dynamic Outer limit Geological province >Inferred >Undefined >Line Unit (Province/ – Readvance contact >Poorly defined >Sharp >Narrow zone Region) – Passive – Interlobate deposit >Defined >Gradational >Wide zone (D), either glacioflu- >Well defined >Diffuse >Undefined Ice (stream) lobe vial or diamicton- distal ice-marginal dominated deposits, moraine zone Lithogenetic contact – Basal till beds (B) Lateral boundary – Lobe/Lobe – Lobe/Interlobate Overlapping areas at the lateral margins of Inner boundaries the provinces (in cases) – For ice (stream) flow, onset zones Flow indications – Lineations – Striations – Other Glacial dynamic Intralobate Geological sub- >Inferred >Undefined >Line Sub-unit – GF province contact >Poorly defined >Sharp >Narrow zone (Sub-province) – Hummocky >Defined >Gradational >Wide zone moraine >Well >Diffuse >Undefined Mixed defined

147 Geological Survey of Finland, Bulletin 412 Jukka-Pekka Palmu, Antti E. K. Ojala, Joonas Virtasalo, Niko Putkinen, Jarmo Kohonen and Pertti Sarala

3 GLACIAL DYNAMIC PROVINCE/REGION GEOLOGICAL MAP UNIT ATTRIBUTES

The definition of the attributes list focuses on the – Lineation and transport directions in the categorising the specific features of the individual active phase(s) units. There is no need to repeat in the attribute – Deglaciation stage development as inter- fields the same information already incorporated preted from the MLG units: esker system in the unit classification (glacial dynamic setting, directions, hummocky moraine field loca- characteristic structural features). tions and characteristics, and also the De • Geological age: Late Weichselian and/or Holocene. Geer moraine fields and their characteristics In the future, the aim is to add older (pre-Late – Physical and compositional characteristics Weichselian) GD spatial units, as for these, the of major MLG features; basal till and related age is an essential attribute drumlin fields, ice-marginal deposits (sys- • Boundaries (o/i) tems), main esker systems, hummocky – 1) outer boundary moraine terrains, de Geer moraine fields, other – 2) lateral boundaries recessional moraines. Older deposits (pre-late – 3) inner boundary Weichselian) are also concisely described • Description: • Former names for the approximately correspond- – Genesis (i): GD-unit-specific history and fea- ing map unit: tures. The description format is separate for • Key references: ice-lobe provinces (and sub-provinces) and interlobate regions:

4 GD PROVINCE AND REGION CHARACTERIZATION

Southern coastal Finland province (SCF) Thus, the lateral boundary of the province is located (Salpausselkien eteläpuoleiset alueet) west of Finland. The lateral boundary towards the The glacial geological development of this province northeast is against the Päijänne interlobate prov- dates from an earlier period (before 13 cal. ka) com- ince and further northwest against the Näsijärvi– pared to the other glacial dynamic provinces. The Jyväskylä ice-lobe province, and still further outer (distal) boundary of this province is outside west-northwest against the Southern Ostrobothnian Finland, towards the south and southeast in Estonia interlobate region. There are flow indications of the and Russia. Ice flow was towards the Pandivere– onset zone in the sea region between Finland and Neva and Palivere ice-marginal positions (Donner Sweden, in the Bothnian Bay area (Greenwood et 1995, Kalm 2006, Rosentau et al. 2009, Kalm 2012). al. 2017). The proximal boundaries of this province are the intensive ice-flow lobe provinces of the Baltic Sea, The Finnish Lake District ice-lobe province (FLDIL) Finnish Lake District and Oulu–Northern Karelia (Järvi-Suomen kielekevirtausalue) GD provinces. For the Finnish Lake District ice-flow GD prov- The ice-lobe provinces of the Younger Dryas ince, the outer boundary zone includes the Younger and early Holocene in the Finnish area of the Dryas stage First and Second Salpausselkäs. There Fennoscandian Ice Sheet are as follows: is evidence from till-covered glaciofluvial deposits of ice-margin readvance from an inner position to The Baltic Sea ice-lobe province (BSIL) the zone of the Salpausselkäs. The lateral bound- (Itämeren kielekevirtausalue) ary towards the southwest is against the Päijänne For the Baltic Sea ice-flow GD province, the outer interlobate region and the border is diffuse. The boundary zone includes the Younger Dryas stage boundary against the Näsijärvi–Jyväskylä ice-lobe First and Second Salpausselkäs and the early province is overriding; the NJIL ice-lobe overrode Holocene Third Salpausselkä ice-marginal depos- part of the former flow area of the FLDIL province, its. This ice-flow system also operated in Sweden, north of Jyväskylä. The northwestern part of the towards the Central Sweden ice-marginal zone. FLDIL, the so-called “trunk” of the ice flow area,

148 Geological Survey of Finland, Bulletin 412 Classification system of Superficial (Quaternary) Geological Units in Finland has sometimes been seen as a separate flow area lobe GD provinces the flow direction varied from (for example, Lunkka et al. 2004). For this area, southeast to south and east. The outer margin of FLDIL and NJIL ice-flow systems were competing, this GD province is mainly in Norway (in the Tana so the boundary is indistinct (Ahokangas & Mäkinen bru – Kirkenes area) and partly in Russia. The Kevo 2013). interlobate fell GD region is located on the western side of the Inari ice-lobe GD province, with a dif- The Oulu–Northern Karelia ice-lobe province (ONKIL) fuse, undefined border. The onset zone against the (Oulun-Pohjois-Karjalan kielekevirtausalue) ice-divide zone is also diffuse and indistinct. For this ice flow province, the flow was towards ice- marginal positions in Northern Karelia and the ice- The Enontekiö ice-lobe province (EIL) marginal positions in Soviet Karelia (Rainio 1996, (Enontekiön kielekevirtausalue) Putkinen & Lunkka 2008). The lateral boundary The Enontekiö ice-lobe GD province flow was towards the southwest was in the Outokumpu area roughly towards the north, towards the ice-mar- against the FLDIL. The ONKIL flow strength was ginal positions in the Finnmark area of Norway, of stronger in the latest parts of the deglaciation, as the Younger Dryas stage. On the western margin of can be seen in the overprinting flow indications. In this ice-lobe GD flow system province is located the the northern boundary of the province, the Ranua Käsivarsi fell interlobate GD region. On the eastern interlobate (RIN) region is the main neighbouring margin, the neighbouring GD province is the Inari region. However, there is also a zone, where the ice-lobe GD province. This margin is diffuse. The boundary is against the Kuusamo ice-lobe province. onset area margin towards the ice-divide zone is diffuse and gradational. Kuusamo ice-lobe province (KIL) (Kuusamon kielekevirtausalue) The Näsijärvi–Jyväskylä ice-lobe province (NJIL) For the Kuusamo ice-lobe province, the ice flow was (Näsijärven-Jyväskylän kielekevirtausalue) towards ice-marginal positions in Russian Karelia The outer margin of the Näsijärvi–Jyväskylä ice- (Putkinen & Lunkka 2008). The lateral boundary lobe GD province is the ice-marginal deposit zone towards the south was against the Ranua interlobate of the Central Finland ice-marginal system. There is GD region. This boundary consists of an interlobate evidence of a readvance of several tens of kilometres esker from Hossa towards the west to Taivalkoski, to this zone. In the southwestern corner of the GD Pudasjärvi and the northern Bothnian Bay. The province, at Hämeenkangas, the margin against the western and northern neighbouring provinces are Baltic Sea ice-lobe GD province is a specific type of the Pello and Sodankylä interlobate regions and the system: NJIL ice flow roughly towards the south and ice-divide zone. The northeastern margin of the almost west-to-east ice movement on the south- GD province is against the Salla ice-lobe GD prov- ern side of the Hämeenkangas interlobate deposit. ince. There is also a small area where the boundary On the western lateral margin of the GD province, is against the Oulu–Northern Karelia ice-lobe GD against the Southern Ostrobothnia interlobate GD province. region, the Pohjankangas interlobate deposit has also been interpreted as an ice marginal deposit with The Salla ice-lobe province (SIL) ice flow from the west (Lunkka & Gibbard 1996). (Sallan kielekevirtausalue) Northwards on the western GD province margin, The Salla ice-lobe GD province is a relatively small the nature of the common border is diffuse. Usually, flow system. The province joins the Kuusamo ice- the margin has been interpreted to be positioned lobe GD province flow system with a gradational along the esker running via Nummijärvi. The mar- common margin. On the lateral margins, the Salla gin between the FLDIL GD province trunk and the GD province is bordered by the Sodankylä and NJIL GD province is complicated and partly diffuse. Savukoski interlobate GD regions. According to Ahokangas and Mäkinen (2013), there is an interstream zone northwest of Kivijärvi and The Inari ice-lobe province (IIL) the Kivijärvi-Lohtaja esker should not be consid- (Inarin kielekevirtausalue) ered as a true interlobate esker, but as an ice-lobe Inari ice-lobe GD province differs from the ice-lobe margin esker, and the Laukaa-Kokkola esker also GD provinces in the ice flow direction, which was gains a possible status as an ice-lobe margin esker. towards the northeast, whereas in all other ice-

149 Geological Survey of Finland, Bulletin 412 Jukka-Pekka Palmu, Antti E. K. Ojala, Joonas Virtasalo, Niko Putkinen, Jarmo Kohonen and Pertti Sarala

The interlobate regions in the Finnish area of the northeastern margin of this GD region is more dif- Fennoscandian Ice Sheet are: fuse and there are two interpretations of where the margin is located. In the southeast of the GD region, The Päijänne interlobate region (PIN) the boundary against the Oulu–Northern Karelia (Päijänteen kielekevirtausten välinen alue) ice-lobe GD province has usually been interpreted An interlobate GD region between the Baltic Sea to be the interlobate esker running from Siilinjärvi and the Finnish Lake District ice-lobe GD provinces through the Iisalmi area towards Pyhäntä. From has its outer margin in the confluence region of Pyhäntä, the GD region border has been inter- the BSIL and FLDIL, where the massive ice-mar- preted to go either southwest of Piippola, north- ginal system of Salpausselkä I was deposited. The west towards Raahe or to have a more extensive eastern lateral margin of this province with the areal northeastern extent, with the boundary going Finnish Lake District ice-lobe province is diffuse, through Kestilä and northwestwards to Siikajoki. In running through the basin of Lake Päijänne. The this interlobate region, there are numerous loca- western margin of this region is the interlobate tions with pre-Late Weichselian stratigraphic units. esker, which runs from Hämeenkoski via Tampere towards the northwest. The northern, inner margin The Ranua interlobate region (RIN) of this region is the boundary with the Näsijärvi– (Ranuan kielekevirtausten välinen alue) Jyväskylä ice-lobe province and its Central Finland The northern margin of this GD region is against ice-marginal system, which was deposited after a the Kuusamo GD province. The margin is diffuse readvance to the ice-marginal position. and poorly defined. The southern margin against the ONKIL GD area is an interlobate esker, run- The Southern Ostrobothnian interlobate region (SOIN) ning east to west from Hossa via Taivalkoski and (Etelä-Pohjanmaan kielekevirtausten Pudasjärvi to the shores of the northern Gulf of välinen alue) Bothnia. There are many locations with pre-Late The SOIN GD region is one of the most complex Weichselian stratigraphic units. GD regions in Finland. There are grounds to divide the region into smaller subregions of Vaasa and Pello interlobate region Suupohja, but to do this we need more information. (Pellon kielekevirtausten välinen alue) The eastern margin of the region is partly sharp, The Pello GD region is located between the bifur- with the Pohjankangas interlobate or ice marginal cated ice-flow subregions of the Kuusamo ice- glaciofluvial deposit the probable deposit delineat- lobe GD province. The margins of this GD region ing the margin. Further towards the north along the are diffuse and poorly described. There are many eastern margin, the nature of the margin becomes locations with pre-Late Weichselian deposits and diffuse and undefined. In the western coastal area stratigraphic units. (Kristiinankaupunki area), an ice-flow system of north–south movement has been recognized. The Sodankylä interlobate region southern margin of the region is against the Baltic (Sodankylän kielekevirtausten välinen alue) Sea ice-lobe GD province, and the nature of the bor- The Sodankylä interlobate GD region is located der is diffuse and gradual. In this GD region, there between the northwest-southeast flow system of are numerous locations with pre-Late Weichselian the Kuusamo ice lobe GD province and the Salla stratigraphic units. small ice-lobe GD province. This province has a diffuse northern margin with the ice-divide zone. The Middle Ostrobothnian interlobate region (MOIN) In this region, there are well-preserved deposits (Keski-Pohjanmaan kielekevirtausten (for example, well-preserved eskers and drumlin välinen alue) fields) of pre-LGM glaciations, from Middle and This interlobate GD region has its southwestern Early Weichselian stages. Consequently, there are margin against the FLDIL GD province in the inter- numerous locations with pre-Late Weichselian lobate esker running from Siilinjärvi via the south stratigraphic units in this GD region. of Pyhäjärvi towards the northwest through Nivala. This interlobate esker disappears before reaching Savukoski interlobate region the coastal area, indicating the cessation of melt- (Savukosken kielekevirtausten välinen alue) water discharge (Ahokangas & Mäkinen 2013). The The Savukoski GD region is bounded towards the

150 Geological Survey of Finland, Bulletin 412 Classification system of Superficial (Quaternary) Geological Units in Finland southwest against the Salla ice-lobe GD province. The ice-divide zone (ID) This area could also be considered as part of a larger (Jäänjakajavyöhyke) ice-divide region (compared with the current spa- The ice-divide zone in central Lapland is sur- tial delineation of the ice-divide zone), which also rounded by both provinces of ice lobes (Kuusamo, includes the Sodankylä GD region. The northern Salla, Enontekiö and Inari) and the interlobate neighbour for this region is the ice-divide zone, regions of Sodankylä and Savukoski. For this region, with a undefined and diffuse margin between these the margins against almost all surrounding prov- regions. inces are gradational and diffuse. In this zone are numerous locations with pre-Late Weichselian Other regions that can be delineated based on ice- stratigraphic units. lobe patters and morpho-lithogenetic characteristics in the Finnish area of the Fennoscandian Ice Glacial dynamic ice-lobe provinces are in some Sheet are: cases divided into distinct and independent or semi-independent sub-lobe provinces. This divi- The Kevo (interlobate) fell region sion can also include subregions or sub-provinces (Kevon tunturialue) of the presently described glacial dynamic prov- The Kevo fell interlobate region is a relatively high inces and regions that were overridden by subse- fell area west of the Inari ice-lobe GD province. The quent (younger) ice flow. These sub-provinces and boundary between these regions is gradational and subregions constitute mappable geological entities. diffuse. Concurrently, well-defined and distinct subprovinces are the following (to be complemented as The Kilpisjärvi (interlobate) fell region work progresses): (Kilpisjärven tunturialue) • The Baltic Sea ice-lobe province (BSIL) The Kilpisjärvi fell interlobate region is a high fell – Loimaa sub-province (BSIL-L) area west of the Enontekiö ice-lobe GD province. • The Finnish Lake District ice lobe (FLDL) The boundary between these regions is gradational – FLDL province sub-region overridden by and diffuse. Näsijärvi-Jyväskylä lobe ice flow (FLDIL-OR)

REFERENCES

Ahokangas, E. & Mäkinen, J. 2013. Sedimentology of an ciation patterns in the Baltic region: Pohjankangas, ice lobe margin esker with implications for the degla- western Finland. Journal of Quaternary Science 11, cial dynamics of the Finnish Lake District lobe trunk. 377–388. Boreas, 1–16. doi:10.1111/bor.12023 Lunkka, J. P., Johansson, P., Saarnisto, M. & Sallasmaa, Donner, J. 1995. The Quaternary History of Scandinavia. O. 2004. Glaciation of Finland. In: Ehlers, J. & Gibbard, World and Regional Geology Series, Volume 7. Cam- P. L. (eds) Quaternary Glaciations – Extent and Chro- bridge, New York, Port Chester, Melbourne, Sydney: nology. Elsevier, 93–100. Cambridge University Press. vii + 200 p. Putkinen, N. & Lunkka, J.-P. 2008. Ice stream behaviour Greenwood, S. L., Clason, C. C., Nyberg, J., Jakobsson, M. and deglaciation of the Scandinavian Ice Sheet in the & Holmlund, P. 2017. The Bothnian Sea ice stream: Kuittijärvi area, Russian Karelia. Bulletin of the Geo- early Holocene retreat dynamics of the south-cen- logical Society of Finland 80, 19–37. tral Fennoscandian Ice Sheet. Boreas 46, 346–362. Rainio, H. 1996. Late Weichselian end moraines and de- doi:10.1111/bor.12217 glaciation in eastern and central Finland. Espoo: Geo- Kalm, V. 2006. Pleistocene chronostratigraphy in Esto- logical Survey of Finland. 73 p. Available at: https:// nia, southeastern sector of the Scandinavian glacia- tupa.gtk.fi/julkaisu/erikoisjulkaisu/ej_017_synopsis. tion. Quaternary Science Reviews 25, 960–975. pdf Kalm, V. 2012. Ice-flow pattern and extent of the last Rosentau, A., Vassiljev, J., Hang, T., Saarse, L. & Kalm, V. Scandinavian Ice Sheet southeast of the Baltic Sea. 2009. Development of the Baltic Ice Lake in the east- Quaternary Science Reviews 44, 51–59. ern Baltic. Quaternary International 206, 16–23. Lunkka, J. P. & Gibbard, P. L. 1996. Ice-marginal sedimentation and its implications for ice-lobe degla-

151 Geological Survey of Finland, Bulletin 412 Jukka-Pekka Palmu, Antti E. K. Ojala, Joonas Virtasalo, Niko Putkinen, Jarmo Kohonen and Pertti Sarala

APPENDIX 2

14.4.2021

MORPHO-LITHOGENETIC (MLG) GEOLOGICAL UNITS IN FINLAND: IDENTIFICATION AND CHARACTERIZATION

J.-P. Palmu, A. E. K. Ojala, J. Virtasalo, N. Putkinen, J. Kohonen & P. Sarala

CONTENTS

1 IDENTIFICATION OF GENETIC DEPOSIT TYPE AND MLG UNITS...... 153

2 NAMING OF MLG UNITS, EXAMPLES...... 153

3 ATTRIBUTES OF MLG UNITS IN FINLAND ...... 154

4 FINSTRATI MLG UNIT ATTRIBUTE DOMAIN LIST TABLES...... 156

REFERENCES...... 167

152 Geological Survey of Finland, Bulletin 412 Classification system of Superficial (Quaternary) Geological Units in Finland

1 IDENTIFICATION OF GENETIC DEPOSIT TYPE AND MLG UNITS

The MLG procedure applied in Finland is presented known and understood, this insight enables geolo- in Figure 1. Landform (morphology) relates to the gists to establish the spatial and temporal associa- shape of the land surface features (slopes, slope tions and complexities between individual deposits breaks, landform patterns), whilst lithology refers and their respective morphological elements. In the to the composition (grain size, mineral composi- early stages of mapping, the emphasis will be placed tion) of a deposit. Using the landform and lithology on observation. Nonetheless, the final step of the elements, a third element – process (the mode of process (Fig. 1) is sensitive to the overall geologi- origin) – may be interpreted. The resulting map cal evolution model and to the presumed deposi- unit is classified according to the Genetic Deposit tional environments as a part of the model. A shared Type (Table 2) and the MLG unit may be defined geological context is a critical requirement for the and named. attempted uniform ‘mapping result’. Glaciodynamic An understanding of the process by which a geo- modelling with GD provinces and regions strongly logical unit was formed is the most essential element supports the development of such a shared context. of superficial mapping. If geological processes are

Fig 1. Simplified interpretation process chart for the morpho-lithogenetic units (modified from Lee & Booth 2006). The genetic interpretation is a ‘two-stage’ process, involving evaluation of the overall depositional context (first step) and interpretation of the genetic deposit type (last step).

2 NAMING OF MLG UNITS, EXAMPLES

The naming of MLG map units comprises a locality/landform name and an MLG map unit class for FinstratiMP (Table 3). Second Salpausselkä Ice-Marginal System Pieksämäki Drumlin Field >Vesivehmaankangas Delta Complex >Paltamäki Drumlin

153 Geological Survey of Finland, Bulletin 412 Jukka-Pekka Palmu, Antti E. K. Ojala, Joonas Virtasalo, Niko Putkinen, Jarmo Kohonen and Pertti Sarala

3 ATTRIBUTES OF MLG UNITS IN FINLAND

MLG units in FinstratiMP are characterized and • GD setting described by the following attributes. The definition Ice-lobe province flow area of the FLDIL province of the attributes list focuses on the handling of spe- • Depositional setting (environment) cific features of the individual morpho-lithogenetic Subglacial setting, glaciolacustrine setting map units. The genetic deposit type is incorporated • MLG Deposit Type in the unit classification and thus not repeated in GFer (Table 3 is also included in the main the attributes. document) • Boundaries (observed/interpreted): criteria for • Landform characteristics observation/interpretation Ridge, straight to curved • Description: • Brief description: – Genesis (i): MLG-unit-specific history and One of the main eskers of the FLDIL province features: SW part… – GD setting for all MLG units • Compositional characteristics – Depositional setting (environment), includ- S, G ing ice margin water depth etc. • Age group: – Genetic deposit type (Tables 3, 4) Late Pleistocene, (Late Weichselian), Early – Landform characteristics Holocene – Brief description • Former names of the corresp. unit: • Compositional characteristics (o/i): lithology and Part of the Asikkala–Joutsa Esker System structures, also including information on deposit • Key references: thickness, if known Fogelberg, Palmu, etc. (see SS II-ice marginal • Geological age: Late Weichselian and/or Holocene. system and..) In the future, the aim is to add older (pre-Late Weichselian) GD spatial units, as for these, the The table of all morpho-lithogenetic units in age is an essential attribute Finland includes the name and the type of unit, and • Former names for the same or approximately the attributes ready to be transferred to FinstratMP corresponding map unit: (see above). A separate table is created in Excel, • Key references: with tables for the MLG unit types (common table an example: structure) MLG UNIT: Pulkkilanharju Esker • Boundaries Bounded by Lake Päijänne, on dry land with fairly sharp borders

154 Geological Survey of Finland, Bulletin 412 Classification system of Superficial (Quaternary) Geological Units in Finland

Fig. 2. Major drumlin fields on the left and major hummocky moraine fields on the right (Mäkinen et al. 2007, MORMI project 2007). The violet lines are the GD ice lobe provinces and interlobate regions (see the main article).

155 Geological Survey of Finland, Bulletin 412 Jukka-Pekka Palmu, Antti E. K. Ojala, Joonas Virtasalo, Niko Putkinen, Jarmo Kohonen and Pertti Sarala

4 FINSTRATI MLG UNIT ATTRIBUTE DOMAIN LIST TABLES

Table 1. Glaciodynamic setting, linked to a defined glacial dynamic ice-lobe province or interlobate region.

Ice-lobe province outer marginal zone

Ice-lobe province flow area

Ice-lobe province lateral margin

Ice-lobe province, internal route

Ice-lobe province onset zone

Interlobate region

Interlobate region, fjeld area

Ice-divide zone

Table 2A. Hierarchical depositional setting attribute domain list: A subset from the Event Environment Vocabulary of the IUGS Commission for Geoscience Information (CGI) Geoscience Terminology Working Group.

Earth surface setting

Glacier-related setting

Englacial setting

Glacial outwash plain setting (links to the glaciofluvial deltaic system setting)

Proglacial setting

Glacier terminus setting

Subglacial setting

Supraglacial setting

Glaciolacustrine (and glaciomarine) setting (missing from CGI)

Deltaic system setting (glaciofluvial ice- contact deltas here)

Delta front setting

Delta plain setting

Lacustrine delta setting

River plain system setting (extramarginal glaciofluvial deposits here)

River channel setting

Braided river channel setting

156 Geological Survey of Finland, Bulletin 412 Classification system of Superficial (Quaternary) Geological Units in Finland

Table 2B. Suffix classification extracts from BGS mapping of superficial deposits (additional depositional setting (environment) information).

Ice Contact

Ice Marginal

Ice Thrust

Lodgement

Melt-out

Subglacial

Sheet or Tabular

Fan or Delta

Table 3. Morpho-lithogenetic unit types for FinstratiMP.

MLG geological unit type Genetic Main Typical landform characteristics deposit lithology* type

Ice-marginal system GFim S, G, (D) An ice-marginal system of delta complexes and other related deposits, with delta plateaus, ice-marginal ridges

>Delta complex GFim S, G, (D) Plateaus, often with the below- mentioned parts

>>Delta (Sandur Delta) GFimd G, S, mS, fS Plateaus

>>Sandur GFims G, S Plateaus, with meltwater channels

>>Proximal ice contact zone unit GFimpic G, S, (D) See below, often overridden, kettleholes

>>Ice-marginal ridge GFimpm G, S,(D) Ridge on top of the plateau (delineates proximal part)

>Ice-marginal ridge GFimr S, G, (D) A separate ridge

Esker system GFe S, G The complete “train”

>Esker GFeb S, G Esker main and linked branches

>>Esker ridge GFer G, S Ridge, also a ridge delineated by kettle holes, with lateral depositional elements (see below)

>>Esker sand (splay) GFes S (G) Esker lateral (and distal) depositional elements

>>Esker delta GFed G, cS, mS, Delta component of an esker fS system

* GEO classification, in English, typical examples: S = Sand, fS = Fine sand, mS = medium sand, cS = coarse Sand, G = Gravel, D = Diamicton, ** For drumlin/lineation: See text

157 Geological Survey of Finland, Bulletin 412 Jukka-Pekka Palmu, Antti E. K. Ojala, Joonas Virtasalo, Niko Putkinen, Jarmo Kohonen and Pertti Sarala

Table 3. Cont.

MLG geological unit type Genetic Main Typical landform characteristics deposit lithology* type

>>Kame area GFek S

>Interlobate esker GFeil S, G Eskers at the boundaries of ice-lobe provinces and/or interlobate regions

Other glaciofluvial deposit, incl. GFex G, cS, mS, extramarginal deposits fS

Till system GTb D

>Basal till GTbb D Veneer or blanket

>Drumlin (lineation**) field GTblf D Lineation fields

>>Drumlin/lineation** GTbl D Linear ridges (now polylines), normally not used as a unit

Hummocky moraine GTh D Hummocky terrains and fields

>Subglacial hummocky moraine GThb “

>>Ribbed moraines GThbr D, (S, G) “, Ribbed moraine geomorphology

>>Murtoo moraines GThbm D, G, S “, Murtoo moraine geomorphology

>Ice contact (passive, partly GThp D, S, (G) “ supraglacial) unit

End moraines (diamicton-dominated) GTim D, (S)

>End moraine ridge (Reunamoreeni- GTimr D, (S) Ridge form, may be multiple combined muodostuma) (can be part of an ice- ridges, mainly in conjunction with ice- marginal delta complex)(Notice the marginal systems material difference to GFimr and GFimpm)

>Recessional moraines, small ridges GTimsr D, (S) (field)

>>De Geer moraine field GTimsrDG D (S) De Geer ridges in fields

>> Minor recessional moraine field GTimsrr D, (S) Usually supra-aquatic or shallow water deposition

Dune field E fS Dune ridge field

* GEO classification, in English, typical examples: S = Sand, fS = Fine sand, mS = medium sand, cS = coarse Sand, G = Gravel, D = Diamicton, ** For drumlin/lineation: See text

158 Geological Survey of Finland, Bulletin 412 Classification system of Superficial (Quaternary) Geological Units in Finland

Table 4. MLG unit-type classification for glacigenic (glacial and glaciofluvial) deposits compared with the classification of the GD map database (15.9.2020).

Code Feature Description MLG unit type for FinstratiMP (see Tables 2 and 3) (genetic deposit type) 1 Glaciofluvial Main class of superficial deposits formed in ice-contact or Not applicable = N/A deposit closely related environments and deposited in fluvial processes by glacial meltwaters. The sediments of the deposits are generally coarse-grained sands and gravels, with minor components of diamictons and fine-grained sediments.

1.1 Esker Eskers are the dominant general type of glaciofluvial deposit, Esker (GFe) usually deposited in an ice-contact environment by glacial meltwaters. Typical deposits are long, continuous ridges with the related lateral and distal depositional elements. The depositional sub-environments are mainly subglacial tunnels, large crevasses and ice margins.

1.1.1 Coarse-grained The dominantly gravelly or coarse sand core element of an Esker (GFe) esker core esker (deposit)

1.1.2 Esker sand Typically the main element of an esker: deposited on top and Esker (GFe) to the lateral and distal sides of an esker core (deposit)

1.2 Interlobate esker An interlobate esker is a ridge type of superficial deposit that Interlobate esker (GFeil) has been deposited by two major ice lobes at their common edge-to-edge contact. These bedforms are typically larger in scale and also coarser grained than eskers.

1.3 Ice-marginal gla- An ice-marginal deposit is a major glaciofluvial deposit type in Delta complex (GFim) ciofluvial deposit Finland and, as the name implies, has been deposited by glacial meltwaters at the ice margin. The material of the deposit is usually sand and gravel, with a minor part formed by diamicton. In large systems, silty sand and silt is also prominent in the deeper distal parts of the deposits.

1.3.1 Delta A glaciofluvial delta is an ice-marginal deposit, in which the Delta (Sandur delta) deposition has continued until the contemporaneous ice lake (GFimd) water level has been reached, i.e. the surface of the deposit is related to the water level during the deposition.

1.3.2 Sandur A sandur is an ice-marginal glaciofluvial deposit (part), where Sandur (GFims) the surface has grown above the depositional stage lake water level. On the surface are typically channels, showing meltwater flow routes towards the deltaic part of the deposit (see above)

1.3.3 Proximal A proximal ice-contact deposit is a proximal ice-marginal Proximal ice-contact zone ice-contact deposit part of a large deposit complex, which is mainly unit (GFimpic) deposit composed of sorted coarse-grained material and a minor compositional component of diamictons. The deposit is typically a ridge and can be depositionally described as a push moraine complex, with glaciotectonic structures. This deposit subtype is related to deposit type 4.1.1, which has the same depositional spatial location, but, due to a different depositional environment and processes, has diamicton-dominated materials.

1.4 Extramarginal A superficial deposit with the sedimentation processes domi- Other glaciofluvial deposit, deposit nated by glacial meltwaters, but in a non-ice-marginal, more incl. extramarginal depos- distal location, for example in a valley further away from the its (GFex) ice margin.

1.5 Littoral deposit Various types of mappable littoral deposits, often related to N/A (L) glaciofluvial deposits.

159 Geological Survey of Finland, Bulletin 412 Jukka-Pekka Palmu, Antti E. K. Ojala, Joonas Virtasalo, Niko Putkinen, Jarmo Kohonen and Pertti Sarala

Table 4. Cont.

Code Feature Description MLG unit type for FinstratiMP (see Tables 2 and 3) (genetic deposit type) 1.8 Buried These deposits are buried sand and gravel deposits that are Esker (GFe) glaciofluvial not recognizable in DEM or shallow geophysical surveys. They deposit are typically overlain by marine or till deposits representing pre-Late Weichselian deposition. Therefore, their identification is based on drilling, reflection seismic and borehole seismic methods. The most typical formation in these classes is an esker.

1.8.1 Buried The main element of a buried esker deposit. Gravel or coarse Esker (GFe) coarse-grained sand are core elements of an esker. esker core

1.8.2 Buried esker The second element of a buried esker deposit. Sand deposits Esker (GFe) sand cover the esker core.

1.8.3 Supposed Typically a continuation of the 1.8 deposit, but not verified by N/A buried drilling. Drilling is an essential method to ensure the lithology glaciofluvial of the deposit lying at 10–100 metres depth below the ground deposit surface.

2 Glacially Glacially lineated terrains were exposed to the subglacial N/A lineated terrain deformation processes. Most commonly, they are till beds modified during the last deglaciation. This main class is not in general mapping use. It is planned to be used for mega-scale glacial lineation (MSGL) generaliza- tions from drumlin 3.1 and megafluting 3.5 datasets in map production.

2.1 Fluted terrain The fluted terrain class is determined for the thoroughly fluted Drumlin (lineation) field (see 3.4 for fluting description) surface of the bed, where large (GTblf) numbers of ridges are present and it is not practical to draw every single ridge crestline. Large concentrations of small fluting ridges are typically located on the thin till surfaces of relatively thin cover till, on the lee sides of bedrock hills. Exam- ple sites are indexed in Rukavaara and Inari.

2.2 Drumlin upland Drumlin upland is a theoretical class to delineate the shield- Drumlin (lineation) field shaped upland areas that typically have thick Quaternary (GTblf) sediment cover, perhaps related to older ice-marginal glaciofluvial deposits. They are relict forms of a shield-shaped (cf. Gluckert 1973) earlier landscape smoothened by a glacier (cf. Möller & Dowling 2015, Eyles et al. 2016). Flutings, drumlins, megaflutings and rarely pre-crags are mapped as polylines on drumlin upland polygons (see 3.1, 3.4 and 3.5 for mapping and bedforms principles). The upland itself is delineated by the morphology of the hill.

3 Glacial Glacially lineated terrain is a main class for mapping glacially Drumlin/lineation (GTbl) lineation lineated beds. In the glaciological sense, the bedforms high- light the glacial erosion of substrates at the base of a deforming subglacial debris layer. Typical features mapped under head class 3 are drumlins and megaflutings (for a review, see 3.1 and 3.5), which are not possible to classify into classes 3.1 and 3.5 due to uncertainties such as urban activities or more natural reasons such as shoreline, fluvial or aeolian processes cutting or masking the start or end point. Sometimes, mega lineations are mapped in this class, because their shape is too vague to be mapped under specific classes below. Palimpsest beds belong to this class, and their relative age is given in the remarks field in the attribute table.

160 Geological Survey of Finland, Bulletin 412 Classification system of Superficial (Quaternary) Geological Units in Finland

Table 4. Cont.

Code Feature Description MLG unit type for FinstratiMP (see Tables 2 and 3) (genetic deposit type) 3.1 Drumlin or Drumlins have a “classical shape” consisting of smooth oval- Drumlin/lineation (GTbl) drumlinoid shaped elongated hills or hillocks with a steeper, often wider and blunter end, the stoss side, pointing in the up-ice direction and a gently narrowing, sloping pointed end, the lee side, facing in the down-ice direction (Fig. 3). This class has a wide variety of forms, not only the classical cigar or cylinder-shaped drumlin, but also less matured and developed drumlinoids, and bedrock plays its own role in the internal structure. They are landforms formed by erosion of the substrates at the base of a deforming subglacial debris layer. Under the (<1metre- thick) deformation till carapace, there are typically remnant sediment bodies with autochthonous cores (Eyles et al. 2016). Drumlins also often exist in swarms or fields of tens or even thousands of drumlins and drumlinoids, representing fast ice flow work in the region. Their elongation ratios used in this process are between 2:1 and 7:1.

3.2 Rock drumlin Rock drumlins on the Fennoscandian shield are always Drumlin/lineation (GTbl) formed when the glacier flowed up and over a bedrock hill, resulting in the steering of the ice side of the rock. They are presumably much older and long-lived bedforms that have been cut and reshaped during successive glaciations. The topography of glacially megalineated bedrock surfaces, once established, may control ice-flow directions during subsequent glaciations. Their size varies from between a few metres to tens of kilometres in scale (cf. Krabbendam et al. 2016). (E. Appendix. Hankasalmi etc.)

3.3 Trough valley or Trough valleys are formed in shear zones or other large N/A crescent trough bedrock valleys that are extensively eroded by crystalline rock boulders present in basal debris. Krabbendam & Bradwell 2014 proposed that trough valleys are formed in old bedrock valleys that have been exposed to long-term erosion and subsequently “rotten rock” has been easily removed by the glacier. Sometimes, tightly spaced trough valleys have bullet noses facing up-glacier. They have resulted from the steering of ice movement by escarpments are presumably much older and long-lived bedforms cut and reshaped during successive glaciations. Crescent troughs belong to the same family of mega-scale bedrock erosional features. They are formed during glacier flow over bedrock hills. Their blunt revolver bullet shape is always eroded down to the crystalline bedrock and they are typically the starting points for megaflutings.

3.4 Fluting Flutings are elongated streamlined ridges of sediment aligned Drumlin/lineation (GTbl) parallel to former fast ice flow (elongation ratio < 7:1). They are usually only a few dozens of centimetres to a few metres high and wide (Fig. 3). Flutings tend to occur in sub-parallel groupings and consist of deformation till (Eyles et al. 2015). Flutings are usually straight or slightly curving, although they may bend and cut the direction around the boulders and then resume a straightforward course. Flutings are often formed downglacier from small bedrock knobs or boulders. Flutings may be hundreds of metres, even kilometres long, but many times smaller in scale compared to drumlins and megaflutings, representing exposure to much lower glacier-based pressures during their formation.

161 Geological Survey of Finland, Bulletin 412 Jukka-Pekka Palmu, Antti E. K. Ojala, Joonas Virtasalo, Niko Putkinen, Jarmo Kohonen and Pertti Sarala

Table 4. Cont.

Code Feature Description MLG unit type for FinstratiMP (see Tables 2 and 3) (genetic deposit type) 3.5 Megafluting Megaflutings (Megaridges: in Eyles et al. 2016) are elongated Drumlin/lineation (GTbl) glacial bedforms that form an erosional continuum with drumlins, representing faster ice flow (Eyles et al. 2016). Their lengths are the longest in our inventory, also representing the fastest ice flow under high glacier-based pressures (elongation ratio < 7:1). Their shape is typically highly variable due to bedrock topography changes and these sediment ridges are naturally more symmetrical than bedforms that exist on the “rough” bedrock region (see Fig. 3). Sediment dominant ridges typically have a (<1-m-thick) deformation till carapace overlying remnant sediment bodies with autochthonous cores (Eyles et al. 2016).

3.6 Pre-crag The so-called ‘pre-crags’ are common features in southwest- Drumlin/lineation (GTbl) ern Finland. A typical feature is flutings (3.4) extending on their upstream side. They are composed of remnant older sediments and record the divergent flow of the erodent layer around an emerging bedrock high (Haavisto-Hyvärinen et al. 1989).

4 Moraine This main class consists of diamicton-dominated superficial N/A deposits with a positive geomorphological landform, i.e. the features are hummocks, ridges, hillocks.

4.1 Ice-marginal Ice-marginal moraines have been deposited at the glacier End moraines moraine margin. This is the hierarchically the highest-level class of (diamicton-dominated) the diamicton-dominated, ice-marginally formed superficial (GTim) deposits.

4.1.1 Large diamicton- A large diamicton-dominated moraine ridge area, often in end End moraines dominated moraine complexes, produced by material being dumped or (diamicton-dominated) dump moraine thrusted. (GTim) in end-moraine complexes 4.1.2 De Geer De Geer moraines (DGM) are small moraine ridges formed at De Geer moraine field moraine the grounding line or deformation during a calving event of (GTimsrDG) the retreating ice sheet (e.g. De Geer 1940, Aartolahti 1972, Lindén & Möller 2005, Bouvier et al. 2015, Ojala et al. 2015). Bouvier et al. (2015) and later (Ojala 2016) argued that DGMs are equifinal landforms with various mechanisms of formation, but when characterized by regular and evenly spaced ridges, they are probably formed annually, or at least very closely represent the local rate of ice-margin retreat. Further- more, most studies agree that their geomorphology represents ice sheet dynamics by indicating the direction of deglaciation and the curvature of the ice margin during the retreat (e.g. Boulton et al. 2001, Lindén & Möller 2005, Ojala et al. 2015). 4.1.3 Minor Minor recessional moraines are supra-aquatic relatives of De Minor recessional recessional Geer moraines. Their thrusted and sheared character together moraine field (GTimsrr) moraine with smaller amounts of glacial melt stream deposits propose their formation at the supra-aquatic glacier margin. These diamicton-dominated ridges have been deposited by glacier bulldozing. Their shape seems to follow the ice margin shape with a height of some tens of centimetres to some metres. They typically form fields indicating glacier retreat in the area. See 4.1.3 for a review; this is the single form of the type class, mapped earlier as a polyline, which could now be delineated as a polygon.

162 Geological Survey of Finland, Bulletin 412 Classification system of Superficial (Quaternary) Geological Units in Finland

Table 4. Cont.

Code Feature Description MLG unit type for FinstratiMP (see Tables 2 and 3) (genetic deposit type) 4.3 Hummocky Hummocky moraine areas of the highest hierarchical clas- Hummocky moraine (GTh) moraine sification level, either the subglacial active ice type or passive type, including hummocky moraine areas of the supraglacial environment. This class is used for ambiguous deposits that are problematic to delineate. 4.3.1 Subglacial A large zone of hummocky moraines deposited under the Subglacial hummocky hummocky active ice. Often related to the transition of ribbed moraine moraine (GThb) moraine fields to the cold bed region. The typical glaciological location (active ice) is in marginal areas of flow corridors and onset zones or other regions of sluggish ice flow. 4.3.2 Ice-contact Hummocky moraine areas that have at least a proportion of Ice contact (passive, partly hummocky the hummocks consisting of coarse-grained material (sands supraglacial) unit (GThp) moraine and other meltwater-related sediments), and mass movement (passive/partly sediments (“flow till”), sometimes also relatively fine-grained active, pro- sediments (silts), deposited in a supraglacial environment, glacial/ice with topographic reversal as one of the key components dur- frontal) ing the time of deposition (cf. Boulton 1968). This hummocky moraine type has been deposited in the relatively passive (stagnant) environment inside the ice margin, in a zone probably a few kilometres wide. Also to be noted is that this type of a deposit has had a sedimentation environment that is either supra-aquatic or with a maximum water depth of 20-30 metres at the adjacent ice margin. 4.4 Ribbed The transversal, active-ice moraine-ridge morphology type Ribbed moraines (GThbr) moraine has been classified as ribbed moraine (Kleman & Hättestrand 1999, Hättestrand 1997, Sarala 2003, 2005). As generalised, the ribbed moraine morphology consists of till ridges transverse to the ice-flow direction. However, there is considerable variation between areas and ribbed moraine types. Further- more, ribbed moraine ridges typical have a bouldery surface or boulder-rich upper till where the lithology of the boulders represents very local bedrock, indicating an extremely short glacial transport distance. The formation of ribbed moraine occurred in the central parts of last Fennoscandian Ice Sheet (FIS), in the transitional zone between the cold-bed and the thawed-bed glacier during the early phase of deglaciation. Conditions for the formation of ribbed moraines were favourable in the zone between 200–300 km from the latest ice-divide zone, i.e. in southern Finnish Lapland and in Ostrobothnia, in western coast areas. In the GD database, the ribbed moraines are described as areas. They are divided into three main subtypes, hummocky ribbed moraine, Rogen moraine and minor ribbed moraine, following the classification presented by Sarala (2003). Fur- thermore, it is occasionally possible to recognise a fourth type, namely crescent ribbed moraine. A crescent ribbed moraine, also described also as a Blattnick moraine in Sweden (e.g. Hättestrand 1997), is a rare ribbed moraine type in Finland, indicating certain subglacial reworking conditions after the formation of transversal ridge cores. The shape of a crescent ridge is more like a half circle, resembling dome-/barchan-shaped dunes. Ribbed moraines form a transitional series with streamlined features in those areas where glacier slid over the transversal ridge topography. In several places, a transitional series can be recognized from hummocky ribbed moraines to Rogen moraines and finally to drumlins and flutings (cf. Aario 1977a, b)

163 Geological Survey of Finland, Bulletin 412 Jukka-Pekka Palmu, Antti E. K. Ojala, Joonas Virtasalo, Niko Putkinen, Jarmo Kohonen and Pertti Sarala

Table 4. Cont.

Code Feature Description MLG unit type for FinstratiMP (see Tables 2 and 3) (genetic deposit type) 4.4.1 Hummocky The hummocky ribbed moraine type (4.4.1) is the most com- Ribbed moraines (GThbr) ribbed moraine mon type in Finland (Sarala 2006). It consists of different sizes of hummocks oriented transversally to the ice-flow direction but not having direct signs of the flow direction.

4.4.2 Rogen moraine The Rogen moraine type is a classical ridge type (cf. Lundqvist Ribbed moraines (GThbr) 1969), which includes a distinct transversal ridge body with heads that bend in the down-ice direction. Sometimes, flutings on the surface of ridges are also found. The signs of the ice-flow direction are an indication of short glacier movement after the formation of the transversal ridge.

4.4.3 Minor ribbed Minor ribbed moraines (4.4.3) only occur in the Sihtuuna area Ribbed moraines (GThbr) moraine in Tervola, southwestern Finnish Lapland. The dimensions are somewhat smaller than of those of the other ribbed moraine types. This moraine type is called a Sihtuuna moraine and was first described by Aario et al. (1997).

5 Covering This main class (5) is used for deposits covering glacier mo- N/A deposit raines or glaciofluvial deposits. Covering deposits are especially significant in relation to glaciofluvial deposits, because their original dimensions are often difficult to verify underneath the overlapping sediment cover that is actually part of the larger hydrogeological system. However, in the Ostro- bothnian area of the Finnish west coast, these deposits can form zones several times wider compared to the completely reworked esker ridge, for which the original area is unmappa- ble with remote sensing techniques.

5.1 Covering littoral Sea currents or shoreline wave action reworked shallow N/A (L) deposit coastal sediments to form sand or gravel deposits. These deposits are often related to glaciofluvial deposits, but fascinating beach ridges and related deposits are also found, which are linked to regions with till and moraine deposits.

5.2 Covering A thin sheet of till resting on the older sediments describes N/A (GTb) diamicton this glacier deposit type the best. The till, which is <4 m thick, is typically massive deformation till with a fluted surface and stands out from the sometimes similar but more variable surface of the large end moraine complexes (4.1.1). There is a thin till cover over the glaciofluvial delta and a small end moraine ridge marking the end of the short period of glacier surge. These deposits relate to glacier re-advance and therefore appear in large end moraine zones.

5.3 Littoral deposit A special case of a diamicton-covered glaciofluvial deposit N/A on covering overlain by littoral sediments. diamicton

7 Ice-marginal This is a main class for large ice-marginal deposits (different Ice-marginal system system components) combined into a single deposit complex polygon. (GFim)

8 Unclassified This feature class consists of distinctive features for which N/A feature (distinc- there is not yet information to classify them into a specific tive feature, but deposit type. there is not yet any information to classify)

164 Geological Survey of Finland, Bulletin 412 Classification system of Superficial (Quaternary) Geological Units in Finland

Table 5A. Landform characteristics (CGI Geologic Unit Morphology, geological body, subset of relevant classes) (IUGS Commission for Geoscience Information (CGI) Geoscience Terminology Working Group).

Arch morphology

Basin shape

Blanket shape

(Boudin shape)

Channel shape

(Column shape)

Fan

Layer shape

Mound

Pipe

Rock body geometry irregular

Trough shape

Table 5B. Landform characteristics, BGS landform classification, could be partly more suitable.

Fan

Plain

Hummocky/moundy terrain

Ridges

Terraces

Blanket

Veneer

Complex

Table 6. Main lithology (grain size).

Main lithology (grain size), Code GEO GEO in English

S Hiekka Sand

>fS Hieno Hiekka Fine Sand

>mS Keskikarkea Hiekka Medium Sand

>cS Karkea Hiekka Coarse Sand

G Sora Gravel

D Moreeni Diamicton (Till)

F Siltti ja Savi Fine sediments (Silt and Clay)

>FC Savi Clay

>FSi Siltti (Hiesu ja hieno hieta) Silt

165 Geological Survey of Finland, Bulletin 412 Jukka-Pekka Palmu, Antti E. K. Ojala, Joonas Virtasalo, Niko Putkinen, Jarmo Kohonen and Pertti Sarala

Table 7. Age group attribute: geological timescale classification from the IUGS Commission for Geoscience Information (CGI) Geoscience Terminology Working Group.

Eonothem / Eon Erathem / Era System / Period Series / Epoch Stage / Age North West European Stages Phanerozoic Cenozoic Quaternary Holocene Meghalayan Northgrippian Greenlandian Pleistocene Late Pleistocene Chibanian Calabrian Gelasian

GTK internal proposition Quaternary Holocene Late Holocene Middle Holocene Early Holocene Pleistocene Late Pleistocene Late Weichselian Middle Weichselian Early Weichselian Eemian Saalian

166 Geological Survey of Finland, Bulletin 412 Classification system of Superficial (Quaternary) Geological Units in Finland

REFERENCES

Aario, R. 1977a. Classification and terminology of- mo ing vs. glacial erosion. Quaternary Science Reviews 95, rainic landforms in Finland. Boreas 6, 87–100. 20–42. Aario, R. 1977b. Associations of flutings, drumlins, hum- Krabbendam, M., Eyles, N., Putkinen, N., Bradwell, T. mocks and transverse ridges. GeoJournal 1:6, 65–72. & Arbelaez-Moreno, L. 2016. Streamlined hard beds Available at: https://doi.org/10.1007/BF00195540 formed by palaeo-ice streams: A review. Sedimen- Aario, R., Peuraniemi V. & Sarala P. 1997. The Sihtuuna tary Geology 338, 1, 24–50. Available at: https://doi. moraine at Tervola, southern Lapland. Sedimentary org/10.1016/j.sedgeo.2015.12.007 Geology 111, 313–327. Lee, J. R. & Booth, S. J. 2006. Quaternary field mapping: Aartolahti, T. 1972. On deglaciation in southern and Lowland Britain. British Geological Survey, Internal western Finland. Fennia 114, 1–84. Report IR/06/99. 78 p. Boulton, G. S. 1968. Flow tills and related deposits on Lindén, M. & Möller, P. 2005. Marginal formation of De some Vestspitzbergen glaciers. Journal of Glaciology Geer moraines and their implications to the dynam- 7: 51, 391–412. ics of grounding-line recession. Journal of Quaternary Boulton, G. S., Dongelmans, P., Punkari, M. & Broad- Science 20, 113–133. gate, M. 2001. Palaeoglaciology of an ice sheet Lundqvist, J. 1969. Problems of the so-called Rogen mo- through glacial cycle: the European ice sheet through raine. Sveriges Geologiska Undersökning C 648, 1–32. the Weichselian. Quaternary Science Reviews 20, Mäkinen, K., Palmu, J. P., Teeriaho, J., Rönty, H., Rau- 591–625. Available at: https://doi.org/10.1016/S0277- haniemi, T. & Jarva, J. 2007. Valtakunnallisesti arvok- 3791(00)00160-8 kaat moreenimuodostumat (Nationally valuable mo- Bouvier, V., Johnson, M. & Påsse, T. 2015. Distribution, raine formations). Ministry of the Environment, Land genesis, and annual-origin of De Geer moraines in Use Department, The Finnish Environment 14/2007. Sweden: insights revealed by LiDAR. GFF 137, 119–333. 120 p. Appendix 5: DVD-diskette. Available at: https://doi.org/10.1080/11035897.2015.10 Möller, P. & Dowling, T. P. F. 2015. The importance of 89933 thermal boundary transitions on glacial geomor- De Geer, G. 1940. Geochronologia Suecica principles. phology; mapping of ribbed/hummocky moraine and Kungliga Svenska Vetenskapsakademiens Handlingar streamlined terrain from LiDAR, over Småland, South III, 18. 367 p. Sweden. GFF 137, 252–284. Available at: https://doi.or Eyles, N., Boyce, J. & Putkinen, N. 2015. Neoglacial (< g/10.1080/11035897.2015.1051736 3000 years) till and flutes at Saskatchewan Glacier, Ojala, A. E. K. 2016. Appearance of De Geer moraines in Canadian Rocky Mountains, formed by subglacial de- southern and western Finland – implications for re- formation of a soft bed. Sedimentology 62, 182–203. constructing glacier retreat dynamics. Geomorphol- Available at: https://doi.org/10.1111/sed.12145 ogy 255, 16–25. Available at: https://doi.org/10.1016/j. Eyles, N., Putkinen, N., Sookhan, S. & Arbelaez-Moreno, geomorph.2015.12.005 L. 2016. Erosional origin of drumlins and megaridges. Ojala, A. E. K., Putkinen, N., Palmu, J.-P. & Nenonen, K. Sedimentary Geology 338, 2–23. Available at: https:// 2015. Characterization of De Geer moraines in Finland doi.org/10.1016/j.sedgeo.2016.01.006 based on LiDAR DEM Mapping. GFF 137, 304–318. Glückert, G. 1973. Two large drumlin fields in central Available at: https://doi.org/10.1080/11035897.2015.1 Finland. Fennia 120, 1–37. 050449 Haavisto-Hyvärinen M., Kielosto S. & Niemelä J. 1989. Sarala, P. 2003. Ribbed-moreenit – jäätikön liikesuun- Precrags and drumlin fields in Finland. Sedimen- nan poikittaiset indikaattorit. Summary: moraines – tary geology 62, 337–348. Available at: https://doi. transverse indicators of the ice flow direction. Geologi org/10.1016/0037-0738(89)90123-1 55, 250–253. Hättestrand, C. 1997. Ribbed moraines in Sweden – dis- Sarala P. 2005. Till geochemistry in the ribbed moraine tribution pattern and paleoglaciological implications. area of Peräpohjola, Finland. Applied Geochemistry Sedimentary Geology 111, 41–56. Available at: https:// 20, 1714–1736. doi.org/10.1016/S0037-0738(97)00005-5 Sarala, P. 2006. Ribbed moraine stratigraphy and forma- Kleman, J. & Hätterstrand, C. 1999. Frozen-bed Fen- tion in southern Finnish Lapland. Journal of Quater- noscandian and Laurentide ice sheets during the Last nary Science 21, 387–398. Available at: https://doi. Glacial Maximum. Nature 402, 63–66. org/10.1002/jqs.995 Krabbendam, M. & Bradwell, T. 2014. Quaternary evolution of glaciated gneiss terrains: Pre-glacial weather-

167 Geological Survey of Finland, Bulletin 412 Jukka-Pekka Palmu, Antti E. K. Ojala, Joonas Virtasalo, Niko Putkinen, Jarmo Kohonen and Pertti Sarala

Additional table. Genetic deposit types used in the GTK MLG map unit classification. An abridged comparison with BGS genetic subdivisions (classes) of natural superficial deposits (McMillan and Powell 1999) is also provided.

GTK classification BGS classification Level 1 >Level 2 >>Level 3 Level 1 >Level 2 >>Level 3

Glacigenic deposits, G

>Glacial deposits, GT

>>Till, basal – includes lineations (drumlins etc.), GTb Glacigenic deposits: >Till (glacial diamicton)

>>Hummocky moraines (with various subtypes), GTh Glacigenic deposits: >Morainic deposits >>Hummocky moraine*

>>Diamicton-dominated end moraines, De Geer and Glacigenic deposits: >Morainic deposits >>Push other recessional moraines (also in groups of ridges) GTim moraine

>Glaciofluvial deposits, GF

>>Eskers GFe Glacigenic deposits: >Ice-contact glaciofluvial deposits >>Esker deposits*

>>Ice marginal glaciofluvial deposits (sandurs, deltas, Proglacial deposits: >Glaciofluvial sheet and subaqueous fan deposits), GFim channel deposits >>Outwash (sandur) deposits* >>Terrace deposits; >Glaciolacustrine deposits >>Lacustrine deltaic deposits >>Beach deposits >>Subaqueous fan deposits*

>>Other glaciofluvial deposits(extramarginal, kames, Glacigenic deposits: >Ice-contact glaciofluvial kame and kettle), GFex deposits >>Kame and kettle deposits*

Basinal deposits, B >Marine sediments BM >Lacustrine sediments BL Includes gyttja

>Glaciolacustrine and glaciomarine sediments, BG Proglacial deposits: >Glaciomarine deposits >>Sea-bed deposits Lacustrine deposits: >Glaciolacustrine deposits

Beach (littoral) deposits, L Coastal zone deposits: >Intertidal deposits >Beach deposits on the higher hillslopes, berms, bars, spits >>Beach deposits; >Supratidal deposits >>Storm >Beach deposits covering lower hillslopes and valleys beach deposits Lacustrine deposits: >Beach deposits >Lacustrine shore face deposits

Fluvial deposits, F Alluvial deposits: >Fluvial deposits >Alluvial fan >Coarse grained fluvial deposits Fc deposits >>Fluvial terrace deposits >Fluvial deposits of variable grain size Fv Lacustrine deposits: >Lacustrine deltaic >>Deltas Fvd deposits

Aeolian deposits, E Aeolian deposits

Organic deposits (peatlands), P Organic deposits>Peat>>Blanket bog peat>> Hill, >Minerotrophic peatlands, fens PCt Raised bog peat*>>Basin peat>>Fen peat*>>Peat >Ombrotrophic peatlands, bogs PSt flow

Mass movement deposits M Mass movement deposits: >Landslip >Talus >Head >Mass movement deposits of fine-grained sediments >Mass movement deposits produced by seismic activity >Solifluction deposits >Talus

Frost action deposits FR

Anthropogenic deposits A Artificial (man-made) ground (no exact correspondence)

168 Geological Survey of Finland, Bulletin 412 Classification system of Superficial (Quaternary) Geological Units in Finland

169 All GTK’s publications online at hakku.gtk.fi

The present volume of the Bulletin of the Geological Survey of Finland summarizes the recent developments in the management of geological units and map data in Finland. The four papers describe: (1) the structure of the new GTK Map Data Architecture, (2) new bedrock classification systems for tectonic-scale map units (geological provinces) and (3) thrust-bounded (tectonostratigraphic) units, and finally, (4) a system for the classification and management of superficial (Quaternary) map units. Combined, these papers outline the modern map data infrastructure, which can be considered as the National Geological Framework in Finland.

ISBN 978-952-217-410-9 (pdf) gtk.fi ISSN 2489-639X (online) ISSN 0367-522X (print)