Bedrock of Finland at the scale 1:1 000 000 - Major stratigraphic units, metamorphism and tectonic evolution Edited by Mikko Nironen Geological Survey of Finland, Special Paper 60, 9-40, 2017 MAJOR STRATIGRAPHIC UNITS IN THE BEDROCK OF FINLAND, AND AN APPROACH TO TECTONOSTRATIGRAPHIC DIVISION by Jouni Luukas1), Jukka Kousa1), Mikko Nironen2) and Jouni Vuollo3) Luukas, J., Kousa, J., Nironen, M & Vuollo, J. 2017. Major stratigraphic units in the bedrock of Finland, and an approach to tectonostratigraphic division. Geological Survey of Finland, Special Paper 60, 9-40, 9 figures, 1 table and 1 appendix. The bedrock of Finland was systematically mapped over 100 years by the Geological Survey of Finland (GTK). The printed maps were lithological maps at the scales 1:400 000 and 1:100 000. The mapping programme was finished in 2005, and bedrock mapping at GTK moved from printed maps to numerical databases. Nowadays, the bedrock map data are collected into a seamless bedrock map database and non-spatial unit database (Finstrati). These databases are based on international vocabularies and are compat- ible with the international standards, and the naming of geological units follows the accepted guidelines and international stratigraphic codes rec- ognized by the Stratigraphic Commission of Finland. The stratigraphic classification into lithostratigraphic and lithodemic units is now the fun- damental basis for bedrock mapping. The major stratigraphic and litho- demic units in Finland according to the Finstrati database are described with restriction into supergroups, supersuites and complexes within four defined tectonic provinces, i.e. Karelia, Svecofennia, Lapland-Kola and Norrbotten. Moreover, the tectonostratigraphic division of northern and eastern Finland is outlined by defining nappe systems and complexes. Keywords: bedrock, data bases, stratigraphy, stratigraphic units, tectono- stratiraphic units, Finland 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 3) Geological Survey of Finland, P.O. Box 77, FI-96101 Rovaniemi, Finland E-mail: [email protected] 9 Geological Survey of Finland, Special Paper 60 Jouni Luukas, Jukka Kousa, Mikko Nironen and Jouni Vuollo BACKGROUND Systematic geological bedrock mapping was carried the databases are now divided into spatial (Oracle/ out by the Geological Survey of Finland (GTK) for ArcSDE) and non-spatial parts (Finstrati, the geo- more than 100 years. The bedrock maps at the scale logical unit register with attribute data in relational 1:100 000, published in the 1900s by the Geological databases) (Vuollo et al. 2011). At the same time, the Survey of Finland (GTK), were lithological, includ- original 1:200 000 scale was changed to a seamless ing rock types and associations, but in the 1990s map database without any specific scale. The 1:200 and early 2000s they also contained stratigraphic 000 and 1:1 000 000 scale products are based on this and structural information. The 1:100 000 scale bed- primary map database. rock mapping programme was finished in 2005 and A non-spatial database of stratigraphic geological replaced by mapping at 1:200 000 scale in limited units (Finstrati) was developed during the DigiKP areas. project. In the construction stage of bedrock map In the first years of the new millennium, the need database, the whole Finnish bedrock was divided to achieve a uniform presentation of the bedrock of into stratigraphic units that had already been in use Finland led to the implementation of a digital bed- in northern Finland. Almost 2400 lithostratigraphic rock map database project called DigiKP, the aim or lithodemic units were generated and described of which was to produce a uniform seamless vec- during the project. The nomenclature was generated tor bedrock map at the scale 1:200 000. The DigiKP according to international rules (North American project was active in 2006–2009. One of the reasons Commission on Stratigraphic Nomenclature, 2005) for this need was the growing interest in and impor- and with the co-operation of the Stratigraphic tance of international cooperation. The year 2005 Commission of Finland (SCF). The role of the SCF was the starting point for the global activity coor- is to provide guidance for stratigraphic procedure, dinated by IUGS (International Union of Geological terminology and revision of geological units in Sciences)/CGI working group (Commission for Finland (Strand et al. 2010). The first classifications the Management and Application of Geoscience of the bedrock into lithostratigraphic and litho- Information) (Vuollo et al. 2011). demic units were carried out in rather small areas At the beginning of the DigiKP project, the data- in central Finland (Laajoki & Luukas 1988, Laajoki base structure was based on traditional lithologi- et al. 1989, Laajoki 1991). This method was adopted cal mapping, because the majority of the source in bedrock mapping in northern Finland during the data (mainly 1:100 000 scale bedrock maps) were 1990s (Lehtonen et al. 1998). lithological maps. In 2007, the database structure The Finstrati unit classification follows either was replaced with a new unit-based approach. The the lithostratigraphic or lithodemic classification. new data model is based on the NADM-C1 (North The preliminary tectonostratigraphy presented at American Data Model Steering Committee 2004) the end of this paper is based on the tectonostrati- definition and supplemented according to nation- graphic classification (Fig. 1). Period and epoch divi- al needs. The original plan for centralized stor- sion follows the classification described in Table 1. age based on an ESRI Geodatabase data structure In the future, Finstrati will be maintained (Oracle/ArcSDE platform) has also been revised, and by GTK in collaboration with the Precambrian Fig. 1. Stratigraphic classification used in the database for Precambrian geological units in Finland (Finstrati). 10 Geological Survey of Finland, Special Paper 60 Major stratigraphic units in the bedrock of Finland, and an approach to tectonostratigraphic division Table 1. Division of Neoarchaean and Palaeoproterozoic periods and epochs, applied from the Finstrati database. Eon Era Period Epoch Age Ma Age Ma from to Ediacaran 635 542 Neoproterozoic Cryogenian 850 635 Tonian Tonian 2 910 850 Tonian 1 1000 910 Stenian Stenian 2 1130 1000 Stenian 1 1200 1130 Ectasian 4 1250 1200 Ectasian Ectasian 3 1280 1250 Mesoproterozoic Ectasian 2 1350 1280 Ectasian 1 1400 1350 Calymmian 5 1440 1400 Calymmian 4 1470 1440 Proterozoic Calymmian Calymmian 3 1520 1470 Calymmian 2 1590 1520 Calymmian 1 1600 1590 Statherian 4 1660 1600 Statherian Statherian 3 1740 1660 Statherian 2 1770 1740 Statherian 1 1800 1770 Orosirian 7 1820 1800 Orosirian 6 1840 1820 Paleoproterozoic Orosirian 5 1870 1840 Orosirian Orosirian 4 1880 1870 Orosirian 3 1910 1880 Orosirian 2 1960 1910 Orosirian 1 2050 1960 Rhyacian Rhyacian 2 2060 2050 Rhyacian 1 2300 2060 Siderian Siderian 2 2400 2300 Siderian 1 2500 2400 Neoarchean Neoarchean 2 2650 2500 Archean Neoarchean 1 2800 2650 Mesoarchean 3200 2800 sub-commission of the SCF. The database now re- making it a centralized reference point for all strati- cords information on all stratigraphic units of bed- graphic unit information on Finnish bedrock. rock in Finland and their usage in the literature, DIVISION INTO MAJOR LITHOSTRATIGRAPHIC AND LITHODEMIC UNITS The following division is based on the identifica- the international convention (Table 1: Orosirian tion of the major lithospheric blocks, i.e. tectonic 1, Orosirian 2, etc.). This chronostratigraphic provinces of Karelia, Lapland-Kola, Norrbotten and classification is presented chronometrically by Svecofennia (Fig. 2; see Nironen, this volume). In using absolute ages, i.e. each eon, era, period and this text, supergroups, supersuites and complex- epoch is defined by an arbitrary numerical age. The es are defined; descriptions of minor units can be unit with age at a period or epoch boundary is con- found in data services linked to Finstrati. The main sidered to be part of the younger period/epoch. Finstrati division is shown in the appendix. The sub- Most of the new units were defined for the bed- division of Precambrian periods into epochs follows rock of southern Finland, and because of the limited 11 Geological Survey of Finland, Special Paper 60 Jouni Luukas, Jukka Kousa, Mikko Nironen and Jouni Vuollo Fig. 2. Chronostratigraphic Period classification of bedrock and tectonic provinces in Finland according to Finstrati. The Karelia Province consists of the Central Karelia and the Western Karelia Subprovinces, and the Svecofennia Province is divided into the Western and Southern Finland Subprovinces. The white areas denote units that were emplaced or deposited after the assembly of the provinces (see Fig. 7). 12 Geological Survey of Finland, Special Paper 60 Major stratigraphic units in the bedrock of Finland, and an approach to tectonostratigraphic division time frame, the division in this area should be con- boundaries are shown. The Karelia Province con- sidered preliminary. We have added remarks on tains large areas of Archaean bedrock partly poorly constrained parts of the division. overlain by Palaeoproterozoic rocks, whereas The crude chronostratigraphic classification of the Svecofennia Province is devoid of Archaean the bedrock is presented in Figure 2. The map dis- rocks. plays the ages of exposed rocks, and the province Karelia Province Slabunov