YEARBOOK GEOLOGICAL SURVEY OF ESTONIA F. R. Kreutzwaldi 5 44314 Rakvere Telephone: (+372) 630 2333 E-mail: [email protected]

ISSN 2733-3337

© Eesti Geoloogiateenistus 2021

2 Foreword ...... 3 About GSE ...... 5 Cooperation ...... 6 Human resource development ...... 9 Fieldwork areas 2020 ...... 12

GEOLOGICAL MAPPING AND GEOLOGICAL DATA Coring – a major milestone in subsurface investigations in Estonia ...... 13 Coring projects for geological investigations at the GSE in 2020 ...... 15 Distribution, extraction, and exploitation of construction minerals in Pärnu county . . . . 17 Mineral resources, geophysical anomalies, and Kärdla Crater in Hiiumaa ...... 22 Geological mapping in Pärnu County ...... 26 Opening year of the digital Geological Archive ...... 29

HYDROGEOLOGY AND ENVIRONMENTAL GEOLOGY Status of Estonian groundwater bodies in 2014–2019 ...... 31 Salinisation of groundwater in Ida-Viru County ...... 35 Groundwater survey of Kukruse waste rock heap ...... 37 The quality of groundwater and surface water in areas with a high proportion of agricultural land ...... 39 Transient 3D modelling of 18O concentrations with the MODFLOW-2005 and MT3DMS codes in a regional-scale aquifer system: an example from the Estonian Artesian Basin ...... 42 Radon research in insuffi ciently studied municipalities: Keila and Võru towns, Rõuge, Setomaa, Võru, and Ruhnu rural municipalities ...... 46 GroundEco – joint management of groundwater dependent ecosystems in transboundary Gauja–Koiva river basin ...... 50

MARINE GEOLOGY Coastal monitoring in 2019-2020 ...... 53 Geophysical surveys of fairways ...... 56 Environmental status of seabed sediments in the Baltic Sea ...... 58 The strait of Suur väin between the Estonian mainland and the Muhu Island overlies a complex bedrock valley ...... 60

Foreword

2020 has been an unusual year that none of us is likely to soon forget. The world has changed, people’s needs and expecta- tions have changed, and the focus is shifting increasingly to resource effi ciency and environmental protection. In order for the green transition to bring economic benefits to Estonia while also safeguarding the environment, and to give our citi- zens confidence in the future, the Geological Survey of Esto- nia (GSE) must contribute to the collection and publication of science-based and fact-based data.

Sirli Sipp Kulli Director of the Geological Survey of Estonia

In the development of our young organisa- the field of geology. Based on the needs tion, the GSE’s third year of operation has and expectations of these parties as well as been comparable to a marathon check- public authorities we have been preparing point, where we took a look around us to an updated development plan for the GSE see whether we have the right competen- for the next five years, which is now nearly cies and are moving in the right direction complete. and at the right pace to restart our coun- try’s economy. We have received a great deal of support from our universities and we look forward At the beginning of the year, there were to the fruits that our ongoing collaboration changes in the GSE’s management. Now projects will bear in the coming years. In our team has expanded and strategic, for- addition to seeing the fact-based research ward-looking goals have been established results that will be produced, we hope to with greater clarity. recruit highly educated geologists for our team from among university graduates. I am extremely pleased that, despite the re- strictions resulting from the Covid-19 pan- We have laid a foundation of knowledge demic, we have managed to establish close and skills and are improving it in order to and open bilateral contacts with both local support the launch of various projects of governments and companies operating in importance to the state, including off shore

EESTI GEOLOOGIATEENISTUS 2020 3 and onshore wind farms, solar farms, a fixed By an emotionally diffi cult decision, but one link with Saaremaa, etc. We assessed the in accordance with the objectives of the on- security of supply of construction miner- going state reform, we resolved to merge als in Rapla County and Pärnu County and the GSE’s laboratory with and transfer the restarted the investigation, interrupted 30 related expertise, gained over decades, to years ago, of major state-owned mineral the Estonian Environmental Research Cen- resources, such as phosphorite and grap- tre. With this, we ensured a better price– tolitic argillite. Furthermore, we launched quality ratio of lab services for both the in- the relocation of our tremendous common stitution itself and businesses, as well as the treasure – the tens of kilometres worth of opportunity for the staff to apply their skills drill cores collected around 80 years ago – in an accredited laboratory. In order to fulfill to modern facilities at Arbavere. our main tasks, we focus on raising geolog- ical competence and involving experts in Concerning one of our key resources, order to make our best contribution to the groundwater, we prepared hydrogeolog- development of the country’s economy in ical maps and maps of the level of protec- the conditions of the green deal. tion of the groundwater in Hiiu County and Rapla County. In addition, last year, our hy- This yearbook provides an interesting drogeologists participated outstandingly overview of our most important projects in several international projects, setting a in 2020 and their results, and also takes a shining example for our other departments. brief look at the future. It contains articles on everything from groundwater surveys, Growing pressure for the exploitation of seabed surveys, and coastal monitoring coastal areas in Estonia has increased the to geological investigations. We hope that need for reliable base data and knowledge. you enjoy the comprehensive articles and The new coastal monitoring methodology the wonderful information and images con- and its further use will allow us to obtain tained therein, and that they provide you more reliable data for the spatial planning with a full overview of the GSE’s activities. and protection of marine and coastal areas and for the mapping of risks. Meanwhile, the completed survey of shipping lanes has provided the Maritime Administration with updated information for dredging projects. Happy reading!

4 GEOLOGICAL SURVEY OF ESTONIA 2020 About Geological Survey of Estonia

State Budget 2018 2019 2020 Labour costs 1 300 000,00 € 1 400 000,00 € 1 400 000,00 € Management costs 729 815,00 € 1 356 000,00 € 1 084 176,00 € Investments 271 000,00 € 450 000,00 € 375 000,00 € (including Arbavere development) Total 2 300 815,00 € 3 206 000,00 € 2 856 176,00 €

Staff Reflection from society (Emor AS survey 14.05-20.05.2020) The average age is 41 years. Should the impact of using geological resources Gender ratio to the environment, economy and social sphere be more investigated in Estonia?

50% Female

68% The impact as a whole should 50% Male be more investigated 16% Don’t know Length of service in the institution (GSE started operating on 01.01.2018) 14% Current study results are suffi cient 2% The impact as a whole can be less investigated 60% Up to 3 years How well are you aware of the fields that the 29% Up to 2 years Geological Survey of Estonia deals with 11% Less than 1 year 65% Rather aware Level of education 18% Rather not aware

17% Not sure 64% MA

21% PhD

15% BA

GEOLOGICAL SURVEY OF ESTONIA 2020 5 ResTA information day (In collabroration with TalTech and TÜ). Photo Sirli Sipp Kulli.

Cooperation

The key question in geological surveying has always been of the Geological Survey of Estonia. The where and how much to research. Today more emphasis is help of the rural municipality governments also put on how to research and what happens after the re- in informing the population was essential in search. Cooperation between researchers, scientists and de- places where the drilling work was carried cision-makers is becoming more and more important to find out. Information was available on the web- answers. The needs of undertakings and the local community sites of the rural municipalities and longer cannot be ignored. explanatory articles were published in local newspapers. Information on the progress of A good example of cooperation from 2020 drilling work was also available on the web- was the construction of boreholes in co- operation with the local governments in site of GSE. The few problems that arose Virumaa. The objectives of research, the were related to the state of the local roads siting of boreholes and the technical side of and were solved quickly. Local governments drilling needed to be explained. The unions have continued interest in the results of the of Lääne-Viru and Ida-Viru County Munic- research and we will definitely introduce the ipalities responded positively to the plans results once they are published.

6 GEOLOGICAL SURVEY OF ESTONIA 2020 We will continue to cooperate with other state agencies. Many surveys have been conducted based on the state agencies’ need to use adequate information to make informed decisions. Examples from 2020 include the survey of fairways at the re- quest of the Estonian Maritime Adminis- tration (now Transport Administration), and at the request of the Ministry of the Environment, the assessment of the sta- tus of groundwater bodies, the seashore monitoring and soil radiation monitoring, and the assessment of security of supply of construction minerals in Pärnu County.

Cooperation with state agencies will also continue in 2021. Issues related to the use of land in existing and prospective depos- its have become more apparent. Particular focus is on the prospects of the supply of construction minerals, especially in Harju County. Developers have taken an inter- est in the geological conditions of the pro- posed areas for off shore wind farms. The Defence Forces have also expressed an interest in using geological information for their needs.

Since its foundation in 2018, the Geological Survey of Estonia has worked very closely with the geologists from the University of Tartu and the Tallinn University of Tech- nology. Undoubtedly, the funding of two projects – ResTA (Support for Research and Development Activities of Resource Valorisation) and RENE (Resources for a Smart Estonia) – by the European Union has contributed to this. As a project part- ner, the Geological Survey of Estonia has acquired the necessary rock material for universities for research. The long-term objective of cooperation with universities is to provide opportunities for the teaching of Cooperation with Environmental Board. geologists and research work. To this end, Photo Jaak Jürgenson.

GEOLOGICAL SURVEY OF ESTONIA 2020 7 National cooperation projects External projects

The assessment of the status of groundwater Estonian-Latvian Interreg project WaterAct bodies (with the Ministry of the Environment) Estonian-Latvian Interreg project GroundEco A study on the causes and origin of increase in LIFE IP CleanEST chloride concentration of groundwater in the town of Sillamäe (EIC) EU-Waterres – EU-integrated management system of cross-border groundwater resources Improving the conditions for preservation of and anthropogenic hazards geological information (EIC) GeoERA Development and application of methodology required for assessing the state of seabed EMODnet Geology sediments (EIC)

Soil radiation monitoring (national) GSE will continue to develop the infra- Seashore monitoring (national) structure of the Arbavere Georesource Research Centre. Business analysis of the spatial data of GSE (SF) So far, hydrogeologists have cooperated Innovative approaches to monitoring and the most with external partners. Cooper- assessing the marine environment and nature ation mainly includes the assessment of values in Estonian sea area (RITA, TalTech) cross-border groundwater resources and Support for research and development activi- human impact, and the development and ties of resource valorisation (ResTA) validation of evaluation methodologies. Resources for a smart Estonia (RENE) Good advice is always appreciated which is why we established the Chamber of Senior Geologists in 2020 and asked outstanding and experienced geology researchers and practitioners to join it. The objective is for them to contribute the Geological Survey of Estonia with their best knowledge in per- forming the tasks laid down in the statutes. We have made great use of this possibility. As a result, our employees have received methodological advice in performing their tasks and increased their competency.

Thank you!

Jaak Jürgenson [email protected]

8 GEOLOGICAL SURVEY OF ESTONIA 2020 Edmund Sides giving Estonian geologists an overview of the PERC standard in a seminar room at TalTech. Photo Hardi Aosaar.

Human resource development

The availability of competent and knowl- PERC Reporting Standard edgeable workers is of key importance for the Geological Survey of Estonia (GSE). It Across the globe, various standards have is no secret that the list of geologists in Es- been introduced for conducting explora- tonia is quite short and modern know-how tions for mineral resources and reporting the in the field of geology frequently has to be results. At present, there are three or four acquired abroad. That is also why we, at well-known standards in use in the world. the GSE, want to increasingly invest in the Due to our geographical location, the GSE development and training of our staff . In has adopted the reporting standard of the 2019, our employees participated in a to- PERC (Pan-European Reserves and Re- tal of 1,807 academic hours of training. In sources Reporting Committee). The gist of all 2020, this number rose to 2,677. Most of the such standards is that all stages of explora- training courses were aimed at improving tion must be documented in extensive detail. the participants’ knowledge of geology and Today, the requirements for these standards teaching them to use the latest software are also well known to investors and banks, applications. as a result of which it is virtually impossible

GEOLOGICAL SURVEY OF ESTONIA 2020 9 and must be subsequently processed using appropri- ate software. As we have also used Meridata’s software to operate existing equipment and interpret collected data, some of what was talked about was already famil- iar to us. However, with each new method/system, the software gains new nuances, which are easier to learn when the developers are right there beside you. Esto- nia’s marine areas still contain many hidden secrets, and now the GSE’s marine geologists can take a step forward in the discovery of these secrets.

Mineralisation and core description training course

Petri Peltonen, PhD, (in the red vest and glasses) explain- Estonian geologists have unfortunately somewhat ing the structure of the geological description database at lost their consistency in the study of crystalline rocks, the research centre at Arbavere. The ‘desk’ is composed of which lie below sedimentary rocks and are only ex- boxes of iron quartzite drill core samples from Jõhvi. Photo posed at the Earth’s surface on the other side of the Johannes Vind. Gulf of Finland. In Estonia, these can only be studied in drill cores of only a few finger-widths thick. To train to secure funding for an extraction project if the ex- our geologists, the GSE invited Professor Petri Pelto- istence of the resources has not been validated in ac- nen, PhD, who is also actively involved in prospecting cordance with a generally accepted standard. for ore and gold, from the University of Helsinki to The training course on the PERC Reporting Standard share his expertise. The aim of the training was both to was conducted by experienced geologist Dr. Edmund acquire up-to-date knowledge about theoretical ore Sides, who has worked as a consultant for various geology as well as to practise drill core description on mining companies for the past 15 years and has ex- metamorphic basement rocks stored at the research centre at Arbavere. The main purpose of the descrip- tensive experience with the PERC’s standard as well tion was to identify occurrences of mineralisation. The as other international reporting standards. most valuable parts of the training course were the Marine geology training courses in Finland discussions about how various aspects of geological exploration should be handled in Estonia in the future. In 2020, the staff of the Department of Marine Geol- ogy received training in Finland. In the summer they WellCAD training course learned to use the Boomer/Sparker seismo-acoustic A single drill core, or rock sample retrieved from the profiler, and in the autumn they practised the installa- earth, and borehole, or the cavity left behind in the earth tion and use of a multibeam echosounder. The training as a result, can provide a significant amount of informa- courses were conducted by Oy Meridata Finland Ltd., tion. In order to interpret all of this information, it has to one of the leading developers and manufacturers of be presented visually in some way, so that the various high-definition marine geophysics products, systems, data can be compared and contrasted. WellCAD is one and software in our region. The training was part of the of the world’s leading software applications in this area. eff orts to upgrade the equipment and methods utilised The word well in the name refers to a borehole, while CAD by the GSE’s Department of Marine Geology, and will (abbr. of computer-aided design) refers to technical draw- enable highly diff erent and diverse information to be ing. The three-day online training course was conducted collected simultaneously during field work. In marine by Mariano Rodríguez, who was closely involved in the geology, large amounts of data are collected at a time development of the software.

10 GEOLOGICAL SURVEY OF ESTONIA 2020 Configuration of GPS antennas and echosounder sensor Screenshot from the WellCAD training course. on Lake Lohja. Photo Sten Suuroja.

ArcGIS Pro user training ESRI GIS software training courses

In the performance of its duties, the Geological Sur- Over the course of the year, a number of our staff vey of Estonia aims to utilise versatile and modern members participated in various ESRI GIS software working methods and software applications. One training courses aimed at facilitating the performance step in working towards this goal is the deployment of their daily job duties. These included, for example, of ArcGIS Pro for spatial data analysis and process- a training course on working with 3D data in ArcGIS, ing. As our Geoinformation Department already which provided an overview of the nature of three-di- possessed the required skills to use this software, we mensional data (3D objects, surface models) as well decided to introduce the application to our staff more as various options for creating 3D data and the cor- widely through an in-house training course. Thus, two responding spatial analysis methods (e.g., surface training sessions, led by Hando-Laur Habicht, were interpolation, etc.). All topics were explored through held in Tallinn for members of diff erent departments. practical exercises. A training course on the utilisation of Python scripts in geoprocessing, meanwhile, pro- The in-house training provided a general overview of vided general skills for the creation of Python scripts ArcGIS Pro and its functionalities and reviewed all of that enable users to automate data management, the basic operations, from launching the software to object editing, geoprocessing, and map production producing finished maps. The participants learned to tasks when using ArcGIS tools. Additionally, an ad- create projects in ArcGIS Pro, include data from var- vanced training course on online maps and smart ap- ious sources in the projects, create new data layers, plications consisted of practical tasks that introduced use basic tools to create and edit spatial data, design participants to web-based ArcGIS tools for creating and prepare printed maps, and share data with others interactive maps and services, as well as various GIS working with spatial data. applications for smart devices.

Johannes Vind [email protected] Sten Suuroja [email protected] Hando-Laur Habicht [email protected]

GEOLOGICAL SURVEY OF ESTONIA 2020 11 GEOLOGICAL MAPPING AND GEOLOGICAL DATA Fieldwork areas 2020

Single study of fieldwork

Department of Marine Geology and Geophysics Department of Geological Resources Shipwreck discovered by the Geological Survey

Study or fieldwork areas

Department of Marine Geology and Geophysics Geoinformation Department Base map: Estonian Land Board Department of Hydrogeology and Environmental Geology

12 GEOLOGICAL SURVEY OF ESTONIA 2020 GEOLOGICAL MAPPING AND GEOLOGICAL DATA

Drilling machine of Inseneribüroo Steiger at the site of the magnetic anomaly in Jõhvi.

Coring – a major milestone in subsurface investigations in Estonia

Geological surveys involve much more than just mitigate the potential socio-economic crisis in Ida- drilling. However, drilling has always been and re- Viru County, but the truth of this matter will have to be mains to this day an indispensable way to obtain judged by future historians. research material that is not exposed on the surface of the Earth. Indirect methods, such as the investi- When was drilling last carried out in the Republic of Es- gation of geophysical fields, can provide a good deal tonia? The answer is: before the Soviet occupation of of preliminary information, but in order to be able to Estonia. The last phosphorite exploration boreholes draw more definitive conclusions, it is necessary to were drilled in the region of the Aseri Deposit way back pull actual material out of the ground. in 1938–1939. So it is understandable why the drill- In the last few decades, it has been repeatedly ing work that has been done in the last two years is of claimed that the state has neglected the investiga- symbolic importance – it is an expression of us, as Es- tion of the subsurface in Estonia. It is likely that such tonians, deciding for ourselves what we want to investi- surveys could have revealed more eff ective ways to gate, with the potential benefits going to us alone.

GEOLOGICAL SURVEY OF ESTONIA 2020 13 GEOLOGICAL MAPPING AND GEOLOGICAL DATA

Today, despite our missteps, drilling work resources began in the summer of 2020 has already begun in all areas of activ- and was concluded in the spring of 2021. ity of the Geological Survey of Estonia. Hydrogeological observation wells were Deep drilling operations are underway in also constructed during the explorations the Jõhvi magnetic anomaly zone. During for phosphorite. These will be used to up- these operations, inclined drilling was per- date the existing model and estimate the formed for the first time in Estonia, due to impacts of potential extraction activities. the near-vertical position of an ore deposit. Unfortunately, drilling operations that are Drilling for phosphorite and secondary necessary for the mapping and explora- tion of construction minerals have been partially postponed, with only a handful of boreholes having been drilled in Pärnu County. In the area of marine geology, drill- ing has yet to penetrate the topmost, one- metre-thick sediment layer. Marine and impact geologists are also hoping to realise a longstanding dream of theirs: to drill into the Neugrund Crater near Osmussaare.

It was excellent of the Geological Survey of Estonia to immediately launch a variety of geological surveying activities instead of confining itself to exploring purely the- Phosphorite fragment in drill core PH004. oretical issues and creating databases. It is almost as if they heard the maxim of my doctoral thesis supervisor: ‘Do it in parallel!’ Thanks to this we can now simultaneously utilise the new digital document collection as well as study fresh drill cores with an un- precedented percentage of recovery at the Arbavere Research Centre.

Now that the conditions have been cre- ated for comprehensive investigation of the subsurface, we, the geologists, have a great responsibility to ensure that this opportunity produces the best results in Fragment of graptolitic argillite in drill core the form of new knowledge. A new era has GA004. begun in subsurface surveying in Estonia!

Johannes Vind [email protected]

14 GEOLOGICAL SURVEY OF ESTONIA 2020 GEOLOGICAL MAPPING AND GEOLOGICAL DATA

Deposit Explo- Boreholes Monitor- Min Max Average or its ration ing wells depth depth depth vicinity areas m m m

Geological investigation permit No. 333901 for Explora- Rakvere 8 8 3 73,6 116,5 96,6 tion Areas of the Kallavere Formation in Virumaa

Geological investigation permit No. 333711 for Explo- ration Areas for a Geochemical Survey of Graptolitic Aseri 8 8 1 20,05 55 37,8 Argillite in Virumaa

Geological investigation permit No. 509155 for Explora- Toolse (6), 721224,64537,3 tion Areas of the Kallavere Formation in Virumaa, Stage 2 Aseri (1)

Investigation permits issued for 2020.

Coring projects for geological investigations at the GSE in 2020

A variety of investigations for phosphorite (found tonian Geological Archive, selected a set of locations in the Kallavere Formation) and graptolitic argillite of potential interest for drilling boreholes. They es- (found in the Türisalu Formation) have been carried tablished the likely coordinates of the exploration ar- out in Estonia in the past. However, some of these eas and the presumed lithological descriptions based investigations were conducted more than 50 years on the old reports. The reports used for this purpose ago. Since then, drilling techniques and laborato- came from diff erent periods, with the oldest dating ry research capabilities have evolved considera- back to 1938 and the latest to 1977. First, in March 2019, bly. Today, it is possible to extract higher-quality applications were filed for the following investigations: drill cores, utilise better analysis methodologies, (1) ‘Exploration Areas for a Geochemical Survey of and perform analyses with greater accuracy. This Graptolitic Argillite in Viru County’ and (2) ‘Explora- allows researchers to detect elements at small- tion Areas of the Kallavere Formation in Virumaa’. The er concentrations. As such, it is also necessary to corresponding geological investigation permits were compare existing datasets on previously identified issued to the GSE in November 2019. The third appli- deposits with information collected using modern cation was submitted in June 2020 under the title ‘Ex- laboratory equipment, in order to prepare even ploration Areas of the Kallavere Formation in Virumaa, more accurate spatial models of known deposits. Stage 2’. The permit was granted in August 2020. Based on the (first two) permits, the GSE initiated pro- In 2019, the Geological Survey of Estonia started the ceedings for a public procurement for drilling services process of application for permits for two geological in May 2020. As a result of the procurement proceed- investigations from the Environmental Board, as well ings, the work was divided into three lots and, corre- as a third in 2020. Preparations for applying for the spondingly, three contracts were concluded with the permits were commenced in 2018 by Johannes Vint aim of obtaining more accurate data, taking into ac- and Jüri Nemliher, who, based on old reports in the Es- count the nature of the boreholes in the investigations.

GEOLOGICAL SURVEY OF ESTONIA 2020 15 GEOLOGICAL MAPPING AND GEOLOGICAL DATA

The drilling contractor was obliged to complete the work to be performed under these contracts was com- contracts for both investigations in October of the menced on 29 October 2020 in exploration area PH011. same year. The contracts provided for triple-barrel cor- It should be completed in the ending of April in 2021. ing operations, extraction of the drill core, storage of the drill core in core boxes, transport of the boxes to the All of the work to date has been carried out using two Arbavere Georesources Research Centre, sealing of the drilling rigs: MI8 and ZBO S15. Unfortunately, drilling, boreholes, and reclamation of the drilling sites. The con- just like other kinds of technical work, does not always tracts were awarded to OÜ Inseneribüroo STEIGER, go without hitches. During the half-year period, the who commenced drilling at borehole GA005 on 6 June more mobile rig – MI8 – had to be shut down twice for a and completed the drilling operations for the first con- longer period to perform repairs. Meanwhile, the larger tracts on 21 October 2020 at borehole PH005. A total and non-mobile rig – ZBO S15 – proved impossible to of 16 boreholes were drilled on the basis of the two ge- be transported to some of the exploration areas due to ological investigation permits, of which eight boreholes the diffi cult terrain. (identifier: ‘GA’) were located in the exploration areas for the geochemical survey of graptolitic argillite and After completion of operations at the investigation the other eight (identifier: ‘PH’) were located in the ex- points, it was and is important to properly rehabilitate ploration areas of the Kallavere Formation. Four of the the work sites and access roads and restore them to 16 boreholes were expanded to serve as groundwater their original condition in terms of visual appearance to monitoring wells and secured with casing in accordance the greatest extent possible. After completion of the with the requirements, and they will be used groundwa- operations, the GSE first inspected the condition of the ter monitoring until the expiry of the permits in 2022. sites in the exploration areas, then measured, where possible, the location coordinates of the boreholes with The public procurement for drilling services to be pro- its GPS, and, only after everything was determined to be vided under the third permit, which allowed for drilling in order, signed the borehole decommissioning reports in seven exploration areas, was launched in September, and the instruments of delivery and receipt for the ex- and was divided into two lots. The third permit is unique ploration areas. For the decommissioning reports, ap- in that, for this investigation, three boreholes are to proval regarding the reclamation of the site also had to be drilled in each exploration area. This is because be obtained from the representative of the landowner. this investigation is being carried out in collaboration between two project groups: ResTA (‘Support for Re- The drilling contractor delivered all of the retrieved drill search and Development in Resource Valorisation’) and cores to the Arbavere Georesources Research Cen- RENE (‘Resources for a Smart Estonia’). The drilling is tre and placed them into storage in the core storage being financed from RENE’s budget. The two projects facilities available there. At Arbavere, the cores will be are intended to produce a greater amount of research studied by the GSE’s geologists, who will draw up de- material in the form of drill cores, which will be shared scriptions of the cores, photograph the cores, and take with researchers from the Tallinn University of Tech- samples, which will then be analysed in various labora- nology and the University of Tartu. The contracts, once tories, including abroad. The objectives of the sample again, were awarded to OÜ Inseneribüroo STEIGER. In analyses can be broadly divided into two: determina- total, from autumn 2020 to spring 2021, drill cores are tion of (1) the physico-mechanical properties of the expected to be extracted from a total of 21 boreholes rocks and (2) the concentrations of various chemical across seven exploration areas. In two of these explo- elements in the rocks. The first samples were delivered ration areas, too, groundwater monitoring wells will be to laboratories in 2020, and the results of the analyses established for the period of validity of the permit. The are expected to come in in 2021.

Kaido Kansi [email protected]

16 GEOLOGICAL SURVEY OF ESTONIA 2020 GEOLOGICAL MAPPING AND GEOLOGICAL DATA

Distribution, extraction, and exploitation of construction minerals in Pärnu county

Six mineral resources have been reg- The need for this arose due to the growth istered as construction minerals in the of the construction sector, which had led Environmental Register: limestone, do- to an increase in the consumption of con- lostone, construction stone from the struction materials and made it necessary basement, sand, gravel, and clay. In 2018, to evaluate the security of supply of local the Ministry of Economic Aff airs and construction minerals. Communications commissioned the new- Studies on construction minerals in Harju ly established Geological Survey of Es- County and Rapla County were carried out tonia (GSE) to evaluate the distribution, by the GSE in 2018–2019. extraction, and exploitation of construc- tion minerals in Harju, Rapla, and Pärnu The study on construction minerals in counties. Pärnu County and their potential and

GEOLOGICAL SURVEY OF ESTONIA 2020 17 GEOLOGICAL MAPPING AND GEOLOGICAL DATA

of Pärnu County where the properties of natural mineral resources can be expected to be suitable for the extraction of con- struction minerals that fulfil the criteria for raw materials needed in the construction industry, especially in road construction. If the construction of public roads and rail- way infrastructure increases in the coming years, as is expected, so will the demand for local construction minerals.

The study was based on geological map- ping data previously collected by the GSE, geological work reports stored in the Esto- nian Geological Archive, and data from the Records of mineral resources of the Envi- ronmental Register (hereinafter ‘the list of deposits’) together with the aggregated bal- Dolostone deposit ance sheets of mineral resources. The study Sand deposit also provided an overview of existing legisla- Gravel deposit tion on the exploitation of construction min- Clay deposit erals and explored possibilities for the use of Deposit with mine alternative construction materials. claim The total area of dolostone, sand, gravel, and clay deposits located in Pärnu County (which occupies an area of 5,418.73 km²) Location of construction mineral deposits in Pärnu County. is approximately 2,810.95 ha or 28.11 km². Thus, these deposits make up 0.5% of the exploitation was completed in 2020. In total area of the county. Pärnu County, there are deposits of lime- stone from the Silurian Period, clay from In the areas of occurrence of dolostone, the Devonian Period, and sand, gravel, and nine dolostone deposits have been regis- clay from the Quaternary Period. tered, which are located in the northern part of Pärnu County, in the rural munici- The purpose of the study conducted in Pärnu palities of Lääneranna and Põhja-Pärnu- County was to provide a comprehensive maa. In addition to the confirmed deposits, overview of the distribution, extraction, and areas of occurrence and of potential have exploitation of construction minerals in the been mapped out in the region. Another county and to analyse the current situation potential area for geological exploration in regards to the security of supply. The work for dolostone is the Valistre region on the also included an evaluation of opportunities border between the rural municipalities of for the supply of construction minerals until Põhja-Pärnumaa and Tori. Further south, 2030 and, in the longer term, until 2050. however, the geological conditions are likely to be unsuitable for the extraction The researchers were tasked with high- of dolostone, as the thickness of the Qua- lighting, based on public interest, any areas ternary cover is greater there, and, south

18 GEOLOGICAL SURVEY OF ESTONIA 2020 GEOLOGICAL MAPPING AND GEOLOGICAL DATA of the Pärnu River, it is underlain by layers of marl and terrigenous clastic sediments dating back to the Devonian Period.

The areas of occurrence of sand consist of large areas covered by glaciolacustrine sediments and sediments from the Baltic Sea. These sediments are either clayey or very fine-grained (with a high content of clay and dust particles) or occur in very thin layers on the ground.

The areas of occurrence of gravel are scattered areas of glaciofluvial sediments, which are most suitable for use as con- struction minerals. However, in Pärnu County, the occurrence of these glacio- Kurevere-Esivere quarry. Photo Janne Tamm. fluvial sediments is limited and thus the amount of registered construction gravel reserves is small compared to the reserves in the list of deposits in Pärnu County, with of construction sand. approximately 111.3 million m³ of economic reserves of dolostone, approximately 48 The areas of occurrence of clay are scat- million m³ of economic reserves of sand tered across Pärnu County, and clay that and gravel, and 9.3 million m³ of economic is suitable for use as a construction min- reserves of clay (the reserves listed in the eral is only found in a few locations. The table also include reserves of associated Arumetsa Deposit is associated with the mineral resources). occurrence of Devonian marine sediments in the bedrock. The reserves in the Vändra At slightly above 0.6 million m³ in 2018, the Deposit and the areas of occurrence of clay volume of extraction of construction min- consist of glaciolacustrine sediments and erals in Pärnu County makes up about 6% of sediments formed during older stages of the total volume of extraction of construc- development of the Baltic Sea. tion minerals in Estonia. Of the construc- tion minerals found in Pärnu County, de- As of 31 December 2018, a total of 62 con- posits of dolostone, sand, gravel, and clay struction mineral deposits were included have been entered into the list of deposits.

Reserves of construction minerals in Pärnu County as at 31 December 2018 (one thousand m³).

Construction mineral No. of deposits Economic proved Economic probable Potentially economic Volume extracted in reserves reserves reserves 2018 aT aR pT+pR 2018. aastal Dolostone 9 34 669,6 76 635,0 12 384,0 293,0 Sand 21 774,1 18 016,1 12 390,0 233,6 51 Gravel 5388,7 3395,0 1000,0 87,6 Clay 2 8106,7 1210,0 272,0 –

GEOLOGICAL SURVEY OF ESTONIA 2020 19 GEOLOGICAL MAPPING AND GEOLOGICAL DATA

For ensuring the security of supply of construc- For ensuring the security of supply of sand and tion limestone in Pärnu County until 2030 and, in gravel in Pärnu County until 2030 and, in the the longer term, until 2050, the following sugges- longer term, until 2050, the following major sug- tions were made in the study report: gestions were made in the study report:

■ Suggestion No. 1: Designate the area of po- ■ Suggestion No. 1: Carry out geological exp- tential in Valistre as an area of geological exp- lorations in areas of potential sand and gravel loration for construction minerals; deposits in order to register additional reser- ves (Potsepa, Taganõmme, etc.); ■ Suggestion No. 2: Carry out geological exp- lorations in the area of the Kaisma Dolostone ■ Suggestion No. 2: Carry out geological inves- Deposit and the Rinnaku Gravel Deposit for in- tigations and geological explorations in the vestigation of the properties of the gravel and areas of occurrence of glaciofluvial sediments the dolostone in order to verify the suitability as well as the areas of occurrence and areas of of these resources for the production of const- potential for the extraction of sand and gravel ruction aggregate and register additional established in the course of geological map- construction mineral reserves; ping and adjacent areas, taking into account the geology, relief, presence of settlements, ■ Suggestion No. 3: Expand opportunities for and any restrictions (protected natural ob- the extraction of construction limestone from jects, etc.); the deposits at Anelema, Koonga, and Kureve- re; ■ Suggestion No. 3: Reassess the reserves of construction sand and gravel recorded in the ■ Suggestion No. 4: Supply Pärnu County, in list of deposits in accordance with the criteria both the short term and long term, with const- established for construction minerals. ruction aggregate produced from high-grade construction limestone from the Väo Forma- tion extracted from the Kunda Deposit.

A more detailed analysis was provided in the study re- construction minerals. However, using this waste ma- garding the security of supply of dolostone, sand, and terial would also incur higher transport costs, particu- gravel, as well as areas of potential for extraction of larly in Pärnu County, and the quality of construction these mineral resources. materials produced from waste material is lower than that of, for example, construction aggregate produced Based on the data collected in the study, in order to ensure the security of supply of construction minerals from high-grade construction limestone. in Pärnu County until 2030, approximately 15.5 million In the longer term, in 2031–2050, approximately m³ of construction minerals are needed, mainly for the 12.7 million m³ of construction minerals will be needed Road Administration (approximately 8.2 million m³) and for the construction and maintenance of public roads Rail Baltica (or ‘RB’, approximately 6.5 million m³). The most important construction mineral deposits in Pärnu in Pärnu County. Other major consumers of construc- County for infrastructure for the RB project are located tion minerals, in addition to the Road Administration up to 45 km away from the planned route. Additionally, and railway infrastructure projects, include local gov- it is possible to use alternative construction materi- ernments, who primarily need construction sand and als, such as limestone screenings and oil shale waste, gravel. Their need for construction materials is primar- which could partially reduce the need for extracting ily related to the construction and repair of local roads.

20 GEOLOGICAL SURVEY OF ESTONIA 2020 GEOLOGICAL MAPPING AND GEOLOGICAL DATA

According to the analysis based on the preliminary have already been submitted or will be submitted in design documents for the Rail Baltica project, there the future. When considering permit applications, are suffi cient reserves of carbonate rocks suitable issuers of permits must prioritise public interests. for the production of construction aggregate in both Pärnu County and Rapla County for the construction The suggestions made in the studies for ensuring the of the infrastructure. However, taking into account security of supply of construction minerals are in- the volume of other roadworks in these counties, the tended to serve as additional information that enables security of supply of high-grade construction lime- local governments to take a position in regards to the stone until 2030 cannot be considered satisfactory, extraction of construction minerals and businesses because from 2024 the Road Administration’s need to apply for permits for geological investigations and for class III construction aggregate for construction geological explorations. and maintenance of public roads will increase. The study was conducted with the assistance of the According to the aforementioned preliminary design local governments of Pärnu County, the Ministry of documents for the Rail Baltica project, the sand and Economic Aff airs and Communications, the Ministry gravel reserves of Pärnu County (as well as Rapla of the Environment, the Estonian Road Administra- County) are critical in terms of both resources with tion, the Environmental Board, the Land Board, and a low and high clay and dust content. It is therefore various experts and operators in the field of construc- necessary to support operators’ applications for ge- tion minerals. ological explorations aimed at registering additional reserves of construction sand and gravel.

In order to ensure the security of supply of construction minerals, it is important to prioritise public interests in Tamm, J., Liivamägi, S., Bauert, H., Pärn, T., Kuivkaev, H. 2020. Ehitusmaavarade levik, kaevandamine ja kasutamine the processing of applications for permits for geologi- Pärnu maakonnas. Uurimistöö aruanne. Eesti Geoloogia- cal exploration and extraction, taking into account the teenistus, Rakvere, 174 lk. actual need for construction minerals in the short term as well as, in the longer term, up to the year 2050. The REFERENCES suggestions made in the study for the planning of geo- 1 logical explorations in Pärnu County were put together “Ehitusmaavarade levik, kaevandamine ja kasutami- ne Harju maakonnas“. EGT, 2018. EGF aruanne nr 8994. on the basis of the data available to and the current un- https://fond.egt.ee/fond/egf/8994 derstanding of the GSE. “Ehitusmaavarade levik, kaevandamine ja kasutami- In the studies published by the GSE on Pärnu County ne Rapla maakonnas“. EGT, 2019. EGF aruanne nr 9334 as well as Rapla County and Harju County, several sug- https://fond.egt.ee/fond/egf/9334 gestions have been made for geological explorations and extraction for the purposes of ensuring the se- 2 “Ehitusmaavarade levik, kaevandamine ja kasutami- curity of supply of construction minerals. In addition, ne Pärnu maakonnas“. EGT, 2020. EGF aruanne nr 9333 areas of potential have been proposed for carrying https://fond.egt.ee/fond/egf/9333 out explorations. The suggestions made by the GSE 3 Regulation No. 52 establishing the procedure and requi- are not intended to rule out the need for extraction or rements for geological investigations and geological exp- exploration in areas which have not been highlighted lorations for mineral resources /…/ https://www.riigitea- in the studies, but for which applications for permits taja.ee/akt/119122018028

Janne Tamm [email protected]

GEOLOGICAL SURVEY OF ESTONIA 2020 21 GEOLOGICAL MAPPING AND GEOLOGICAL DATA

Kärdla Crater Zone on the geological map of the bedrock of Hiiumaa, and the mineralisation zone near Lennuvälja Road (bottom right corner).

Mineral resources, geophysical anomalies, and Kärdla Crater in Hiiumaa

In 2020, the GSE completed a set of maps of Hiiumaa and the accompanying explanatory notes for the geological base map of Estonia, where the focus was on mapping the Hiiu- maa Uplift on the basis of geological and geophysical evidence, the mineral resources of the Kärdla Crater Zone and their occurrences, assessing the economic potential of the Kaevatsi Magnetic Anomaly, and reviewing the history of oil exploration in Hiiumaa. The Kärdla Crater Zone is noteworthy as it contains a number of mineral deposits (including gravel, construction limestone, technological limestone, clay, mineral water, crystalline construction stone) and occurrences (polymetallic mineralisation, natural bitumens).

22 GEOLOGICAL SURVEY OF ESTONIA 2020 GEOLOGICAL MAPPING AND GEOLOGICAL DATA

The most striking aspect of Kärdla Crater of crystalline construction stone has been is the gravitational field, which has a den- located at a depth of only 15–25 m below sity of 9 points per square kilometre in the the ground on the rim of the crater. In 1985– area around the crater. The residual gravity 1993, mineral water sold under the brand anomaly (i.e. the shorter-wavelength com- name Kärdla was extracted from Soovälja ponent of the physical field) has a statisti- borehole K18, which, until recently, devel- cally significant correlation with geological opers have expressed an interest in from structures, which can be used in geological time to time. mapping. However, the aboveground rim of the crater is not the only cause of the an- One of the most exciting and fascinating nular anomaly – deeper basement struc- mineral occurrences in the area of the tures created during the meteorite impact, Kärdla Crater is a sulphide mineral oc- where heavier rocks underlie lighter frag- currence discovered in 1990 during deep mented rocks, also play a role. mapping operations near the road from Paluküla to the airport. Borehole F374 was The Partsi Gravel Deposit has partly formed drilled in the area of a lead anomaly previ- due to the sandspit jutting out from the rim ously discovered in the soil using the sorb- of the crater. Occurrences of technologi- ent method. The borehole revealed a layer cal and construction limestone have been of dolomitic and sulphide-impregnated located in the deposit of cryptocrystalline limestone up to 5 metres’ thick in contact limestones of the Rägavere and Saunja with the deposit of limestone and greatly formations covering the crater’s rim. A de- deformed pre-explosion Cambrian sand- posit of ceramic clay has been located in stone and clay that covers the crater at the Soovälja Zone. In Paluküla, a deposit a depth of about 40 m below the ground.

6550000

Kärdla kraater

6540000

6530000

Kaevatsi laid 6520000

0km10 20

6510000 390000 400000 410000 420000 430000 440000 450000

Gravitational field with Bouguer corrections (Δg).

GEOLOGICAL SURVEY OF ESTONIA 2020 23 GEOLOGICAL MAPPING AND GEOLOGICAL DATA

10 m northeast and 30 m northwest of the first borehole (containing ore), did not contain any ore. Drilling a borehole to the southeast of borehole F374 was not possi- ble due to the road built in that area.

The limited distribution of the body of ore next to Lennuvälja Road is also indicated by the fact that, in borehole 381, about 200 m to the northwest of borehole F374, where a lead anomaly has also been recorded in the soil during geochemical mapping, rocks that are in a similar situation (in con- Ore body in the drill core extracted from borehole F374. tact with Vasalemma detritic limestone and greatly deformed Cambrian sandstone and clay at a depth of about 40 m) bear no traces of mineralisation or even dolomite. Thus the claim that the anomalous con- centrations of elements recorded in the soil are related to bodies of ore situated deeper underground may not always be true. Also in the section of earth penetrated by bore- hole F178 on the Tubala side of the crater, where the anomalous concentrations of Pb and Zn are related to the lime-sandstone of the lower layers of the Kahula Formation (the former Idavere Substage), located at a depth of about 140 m, there are no Pb or Zn Hand specimen from the drill core extracted from borehole F374 at a depth of 45.4 m: brown (sphalerite), dark grey (galenite), white and anomalies in the soil layer situated above light grey (calcite and dolomite). the 12-metre-thick marine sands.

The sulphide mineralisation in Kärdla is in It contained up to 20% Zn (average: 0.5%), essence similar to Mississippi Valley-type up to 2% Pb (average: 0.2%), and up to low-temperature hydrothermal miner- 0.6% Cu (average: 0.05%). After geochem- alisation events. In Kärdla, the mineral- ical mapping of about 40 km² of the crater isation has largely occurred due to the zone, which also confirmed the presence presence of crevice systems that pro- of lead and zinc anomalies in the soil in mote the release of fluids carrying sul- the area of the borehole, three additional phide ores, and not so much due to the boreholes were drilled near borehole F374. lithological-structural traps that promote Only one of them, located 10 m southwest their concentration. Both the crevice of the first borehole, revealed a body of systems and the lithological-structural ore at approximately the same depth and traps have formed as a result of the me- in a similar situation. The other two bore- teorite impact that occurred in Kärdla holes, which were drilled, respectively, around 455 million years ago. The release

24 GEOLOGICAL SURVEY OF ESTONIA 2020 GEOLOGICAL MAPPING AND GEOLOGICAL DATA of fluids carrying sulphide mineral ores occurred in at least three stages and millions of years later, and it was probably related to the cycles of tectonic acti- vation that took place at that time.

According to highly speculative calculations, a 5-me- tre-thick body of ore weighing about 100,000 tonnes in 6525000 an area of about 1 hectare near Lennuvälja Road could contain up to 500 tonnes of Zn, 200 tonnes of Pb, and 5 tonnes of Cu. In Estonia, where no bodies of polym- etallic sulphide ores have previously been found, this is by far the largest instance of mineralisation discovered, but unfortunately it does not have any potential for min- 6520000 eral resource extraction. In the Kärdla Crater Zone, for there to be potential for mineral resource extraction, the body of ore would have to be tens if not hundreds 0 1123km2 3 km of times larger in volume, and the concentrations of Väinameri useful components would also have to be several times 436000 440000 445000 449000 higher. However, there is simply not enough space for the existence of such a ‘dream’ ore deposit in the Kärdla Crater Zone, which has already been comprehensively -400-200 0 200 400 600 800 1000 1200 1400 T, nT explored through around a hundred boreholes and Δ geophysical methods. Residual magnetic anomaly on the islet of Kaevatsi. In addition to Kärdla Crater, anomalies have also been found on the islet of Kaevatsi. The source of the mag- netic anomaly (with a peak value of 1,800 nanoteslas) deposits on the islet of Kaevatsi contain an estimated on the islet of Kaevatsi may well be a body of ore, as 100 million tonnes of ore, which corresponds to an av- there are no other naturally occurring minerals that eraged-sized iron ore deposit. The deposit in Jõhvi, could produce such a strong magnetic field. Accord- by extension, should contain around 1 billion tonnes ing to magnetometric and gravimetric data, the centre of iron. A comparison of the ore body on the islet of of the body lies at a depth of 500 metres (Štokalenko, Kaevatsi with that in Jõhvi yields that the iron ore in 2017). The depth to the bedrock on the islet of Kaevatsi the former is richer than the latter. Given that mag- is 300 metres, and the nearest borehole is located at a netite is a relatively heavy mineral that causes gravity distance of 4 km from the peak of the anomaly. Con- anomalies and that there is no such anomaly on the sidering the flight altitude at which the aeromagnetic islet of Heinlaid, northeast of the islet of Kaevatsi, any surveys were conducted, the anomaly on the islet of magnetite deposits on Heinlaid thus cannot be very Kaevatsi is about three times weaker than the Jõhvi large, although there is a relatively strong magnetic Anomaly. Judging by the gravity anomaly, the iron anomaly there.

Kalle Suuroja [email protected] Anu Veski [email protected] Mihkel Štokalenko [email protected]

GEOLOGICAL SURVEY OF ESTONIA 2020 25 GEOLOGICAL MAPPING AND GEOLOGICAL DATA

Digitized 1:50 000-scale 1:50 000-scale geological Pärnu area geological map manuscript maps

Geological mapping in Pärnu County

In 2020, the geological mapping was completed in Pärnu (works 2910 and 3023 in the Geological Archive, Pärnu County, more specifically on the Pärnu-Jaa- respectively). In addition, the so-called Uulu-Leina ob- gupi (5334), Pärnu (5332), Häädemeeste (5314) and ject (Geological Archive 3391) of approximately 212 km² Ikla (5312) sheet of the Estonian Basic Map (at a mapped at a scale of 1:50,000 for the purposes of land scale of 1:50,000) in a total area of 1,760 km². improvement was completed in 1976.

Numerous construction and hydrogeological works as After validation and harmonisation, the data on the well as mineral resources prospecting and exploration nearly 1,400 boreholes that were drilled for other pur- have been carried out over the years in Pärnu County. poses in the previous years were also added to the We can speak of geological mapping that contains factual material database Faktika. During fieldwork, generalised and visual data on the earth’s crust in that the unmapped areas at a scale of 1:50,000 were cov- region only in respect of maps and explanatory notes ered with a network of 7,500 monitoring points and that where prepared at the end of 1960s at a scale of outcrops. In the process, dozens of Earth Sciences 1:200,000 (1 cm = 2 km) on the sheet of Limbaži and students and graduates of the University of Tartu and

26 GEOLOGICAL SURVEY OF ESTONIA 2020 GEOLOGICAL MAPPING AND GEOLOGICAL DATA

All mapping sheets of Pärnu County

Well (1444) Borehole (1368) Observation point, outcrop (7549)

Häädemeeste sheet

Well (184) Borehole (314) Observation point, outcrop (2128)

Ikla sheet

Well (38) Borehole (48) Observation point, outcrop (530)

Factual material used for geological mapping in Pärnu County (as of 11.12.2020) the Tallinn University of Technology gained Additional tools for compiling the geolog- their first geological fieldwork experience. ical maps were the Digital Terrain Model, In order to specify the distribution of buried hillshades and orthophotos of the Land valleys, five seismic reflection profiles with a Board, as well as maps from a variety of ap- total length of more than 24 km were com- plications. missioned from the Geology department Using all this data, a set of geological maps of the University of Tartu.To gain a better that includes two base maps was prepared understanding of the relationship between – the bedrock geology map and the map the Quaternary cover sediments and bed- of Quaternary deposits. With the addition rock deposits, seven cored boreholes with a of six supplementary maps: 1) bedrock re- depth of up to 52 m and 62 shallow (less than lief, 2) thickness of Quaternary deposits, 3) 10 m deep) boreholes were drilled. If we in- geomorphology, 4) gravity anomalies, 5) clude these more than 1,400 boreholes that aeromagnetic anomalies, 6) aeromagnetic were in that same area in the borehole data- residual anomalies. base of the environmental register, the data of more than 10,300 monitoring points was Since no deep structural boreholes provid- used to compile the geological maps. Nearly ing new information were drilled in the area, 2,000 of them also exposed the bedrock. the understanding of the deep geology of

GEOLOGICAL SURVEY OF ESTONIA 2020 27 GEOLOGICAL MAPPING AND GEOLOGICAL DATA

m

Holocene alluvial deposits Silt Holocene marsh deposits Fine sand Litorina Sea deposits Sand of diff erent Ancylus Lake deposits grain size Glaciolacustrine deposits Coarse sand Glaciofluvial deposits Pebble Glacier deposits Bog peat Bedrock Varved clay

Geological cross-section of Quaternary deposits (Häädemeeste sheet).

the area remained roughly the same. How- adequately monitored. The failure along ever, the approach to near-surface geol- the shoreline from Häädemeeste to Ikla ogy changed significantly compared to the that probably continues all the way to Lat- past, in particular, the approach to bedrock via and the land side of which has sunk 10– relief and the associated superficial depos- 15 m (or the rocks there were eroded before its as well as the thickness of Quaternary or in the beginning of the Devonian period) deposits. Instead of the northeast-south- is somewhat clearer. This failure explains west trending Treiman buried valley that both the surprisingly straight coastline of borders the southern border of Estonia the region in Estonia, the weirdly narrow and that is often considered the deepest north-south trending superficial deposit buried valley in Estonia, a much more com- of the Narva formation and the outcrops in plex system of valleys is now emerging that estuarine areas of coastal rivers. It is likely can change even further with future re- that a similar failure with a sunken eastern search, especially at the Southern border. wing of 5–10 m or more borders the west- However, in contrast to deep valleys, areas ern edge of the Sakala Upland south of with a thin Quaternary cover of less than Urissaare. 1 m are widespread. There are 92 km² or more than 8% of these (notional Devonian alvars) in the central and southern part of the area, in the distribution area of Devo- nian sandstones, clays and marls. Bedrock Kuldev Ploom [email protected] deposits have numerous failures but due Katrin Kaljuläte [email protected] to the thickness of the Devonian strata, the Eveli Sisas [email protected] absence of good benchmarks and the lack Hando-Laur of geological boreholes, they cannot be Habicht [email protected]

28 GEOLOGICAL SURVEY OF ESTONIA 2020 GEOLOGICAL MAPPING AND GEOLOGICAL DATA

Opening year of the digital Geological Archive

The web application of Estonian Geological Archive Usage activity can also be seen to be lower in the was released in May 2020 with the support of the summer, which is likely to be due to the summer being European Regional Development Fund. Over 7,600 both the season of field work and of holidays. papers describing local geology became immedi- ately available for researchers, geologists, offi cials, Among users, interest appears to be particularly con- and other interested parties. stant in the research report on the security of supply of construction minerals in Harju County, published Since the publication of the digital archive, all new by the Geological Survey of Estonia in 2018, which was research reports received by the Geological Archive also the most downloaded report of 2020. Meanwhile, have been submitted via the web application. In-per- the most popular new publications were the reports son visits and e-mail enquiries, too, have been re- prepared within the framework of the programme for placed by independent queries for information and research and development in resource valorisation downloading of the desired files from the website of (ResTA). As seen in the graph, a sudden spike in the the Geological Archive. While previously delivered re- number of users of the archive occurred on the date of ports are still available in paper form, since the launch the ResTA information day hosted by the Geological of the web application, the Geological Survey has Survey of Estonia and the Estonian Research Council. been contacted only a few times with requests to use them or to verify the quality of the scanned materials. Feedback

Statistics At the end of November, we conducted satisfaction surveys among the users of the Geological Archive In 2020, the Fund has been visited by more than 1,600 and parties who had submitted reports to the archive. diff erent users and more than 32,000 sessions have In addition to gauging satisfaction with the service, been registered. we collected suggestions for the further development

GEOLOGICAL SURVEY OF ESTONIA 2020 29 GEOLOGICAL MAPPING AND GEOLOGICAL DATA

the reports. In addition, users will be able to download Access is provided EGF000 for the user based multiple report files at the same time. AvTS ContactCont the on the permission §35 lg 1 authorauthor or owner Permission sent to p 17 Report All further improvements to the application have been fforor ppermissione [email protected] commissioned based on the adage: ‘Measure twice, cut once.’ By mapping existing problems and thinking through the changes needed, we try to ensure that Requesting of access to a restricted report. the commissioned improvements fulfil their purpose

The archive contains materialsmaterials AdAdditionalddditio files created and leave users satisfied with the service for a long in a variety of formats: fromfrom whenwhe analysing the time to come. scanned manuscripts ttoo materialsmamater may be sent machine readable files to [email protected] Systemization of data in the Geological Archive

EGF000 The web application of the Geological Archive pro- vides us with a better overview of the data available in We will add your contribution Report to the supporting files on the the archive and allows it to be managed more conven- details page of the report iently. This, in turn, has created favourable conditions for the systemisation of the metadata in the Geologi- cal Archive. Thus, first we transliterated over 2,600 ti- Help us improve the usability of old reports. tles in Russian, which had been recorded in Latin char- acters due to the text encoding that was selected for of the web application. We were glad to learn that over the old database. In the course of an extensive meta- half of the respondents were either somewhat satis- data review, we corrected titles and authors’ names fied or very satisfied with the web application of the that were either incomplete or incorrect. Additionally, Geological Archive. Feedback was most positive in re- we added previously missing summaries and key- lation to the quality of the downloaded files, which was words where needed to the reports’ metadata. The the greatest priority of the digitization project. purpose of the corrections was to prevent occasions where users of the Geological Archive are unable to Meanwhile, the biggest bottlenecks for users were que- find a report of interest due to the incorrect labelling. ries and the downloading of files. The process of submit- ting new materials to the archive could also be further Users can also contribute personally to improving the improved. Additionally, we discovered that many users usability of the information contained in the archive. of the Geological Archive were not aware of the possibil- As older records in the archive are stored as scanned ity of requesting personal access to restricted reports. images, retrieving data from them and systemising the data is often up to the users themselves. Sys- Upcoming improvements temised data tables, geo-referenced maps, and other such materials that could be of help to the future users The feedback received has been taken into account of a report are always welcome for storage in the ar- in the planning of further improvements to the ap- chive. We also encourage all users to actively provide plication of the Geological Archive, and some of the us with feedback both regarding any issues as well as requested updates should already reach users by the ideas for further improvements. first quarter of 2021. Based on user feedback, we will be adding a new file group for photographs, and the WFS service will get a new field for permanent links to

Rauno Torp [email protected] Jekaterina Nezdoli [email protected]

30 GEOLOGICAL SURVEY OF ESTONIA 2020 HYDROGEOLOGY AND ENVIRONMENTAL GEOLOGY

Status of Estonian groundwater bodies in 2014–2019

23 October 2000 saw the adoption of Directive In the course of the project, the database was im- 2000/60/EC of the European Parliament and of the proved, cleaned, and systemised, a methodology Council establishing a framework for Community was developed for nine tests to assess the chemical action in the field of water policy (hereinafter ‘Wa- and quantitative status of groundwater bodies, an ter Framework Directive’ or ‘WFD’). According to assessment of the status of groundwater bodies was Article 4 of the WFD, one of the environmental ob- carried out, and recommendations were drawn up jectives of the directive is to improve the status of for the action plan of the water management plan for groundwater bodies and to assess it every six years. the next period. At the request of the Estonian Environment Agency, in 2020, the GSE carried out an assessment of the According to the results of the tests performed, the status of groundwater bodies in Estonia, using data overall status of 8 out of 31 groundwater bodies (bod- from the national groundwater monitoring network, ies No. 2, 6, 7, 11, 15, 24, 27, and 31) was found to be poor. which were collected during the period of the previ- Meanwhile, for 10 groundwater bodies (No. 1, 3, 4, 8, ous water management plan. 9, 12, 20, 21, 28, and 29), the status was assessed as

GEOLOGICAL SURVEY OF ESTONIA 2020 31 HYDROGEOLOGY AND ENVIRONMENTAL GEOLOGY

Cambrian-Vendian Gdov Ida-Viru Ordovician oil shale Pandivere Silurian-Ordovician Middle-Lower Devonian in Meltsiveski Quaternary basin in W-Estonian RBD W-Estonian RBD Cambrian-Vendian Voronka Hiiumaa Silurian-Ordovician Pandivere Silurian-Ordovician Middle-Lower Devonian in Männiku-Pelguranna in E-Estonian RBD E-Estonian RBD Quaternary Cambrian-Vendian Saaremaa Silurian Adavere-Põltsamaa Silurian- Middle Devonian in Prangli Quaternary Ordovician W-Estonian RBD Ordovician-Cambrian in Harju Silurian-Ordovician Silurian-Ordovician beneath Middle Devonian in W-Estonian RBD Devonian in W-Estonian RBD E-Estonian RBD Virumaa Ordovician-Cambrian Matsalu Silurian-Ordovician Silurian-Ordovician beneath Middle Devonian in Koiva Groundwater body borders: in East-Estonian RBD Devonian in E-Estonian RBD RBD Marandi A, Osjamets M, Polikarpus M, et al. 2019. Põhjaveekogumite piiride kir- Tartu Ordovician-Cambrian in Pärnu Silurian-Ordovician Ruhnu Middle-Lower Devonian Upper Devonian East-Estonian RBD jeldamine, koormusallikate hindamine ja hüdrogeoloogiliste mudelite koostamine. Silurian-Ordovician in Kihnu Middle-Lower Devonian Vasavere Quaternary EGF:9110. Ida-Viru Ordovician E-Estonian RBD

Groundwater bodies of river basin districts (RBD) in Estonia.

good, but at risk. The reliability of each test large pumping volumes from the oil shale was assessed pursuant to the methodol- mines on the overall natural resource of the ogy. In general, the reliability of the tests groundwater body, as well as for the Qua- was found to be low. ternary Vasavere groundwater body (27), where groundwater pumping has aff ected High NH4 high concentrations and PHT the water levels of Lake Martiska and Lake values were the main factors causing the Kuradijärv. poor chemical status of the groundwater bodies or defining the groundwater bod- In addition to the other suggestions made on ies being at risk. A poor quantitative sta- the basis of the work carried out, during the tus was identified for the Ordovician Ida- period of the next water management plan, Viru oil shale basin groundwater body (7), it is recommended to identify the reasons which is associated with the impact of the for the increase in the PHT and NH4 values

32 GEOLOGICAL SURVEY OF ESTONIA 2020 HYDROGEOLOGY AND ENVIRONMENTAL GEOLOGY in the upper groundwater bodies in par- reserves are practically impossible to sep- ticular, as well as to improve and update the arate. This, in turn, would make it possible existing groundwater monitoring network. to improve the monitoring system and in- Furthermore, due to the relevant hydroge- crease its representativeness and reliability. ological conditions, it is recommended to When constructing future water intakes, the merge groundwater bodies No. 17 and 21 as drilling of boreholes within the Voronka and well as 18 and 22, as they belong to the same Gdov groundwater bodies, that open both of aquifer in terms of hydrodynamics and their them, must not be permitted.

Background check Good status. for the period of 2014-2019. Further assement NO Are there any average values of chemical status higher than TV in observation is not required. wells?

YES

Good status Test 1 according to the 1st test. Is there overlimit in more NO Proceed with further than 20% of GWB area? tests of chemical status (high confidence).

YES

Trend assessment I Good status according Trend assessment II Assess the trend of to the 1st test. Is there any substances. Is the trendline NO NO Proceed with further substance with of any substance higher than tests of chemical status upward trend? 75% of TV? (low confidence).

YES

Confidence Bad status NO Too few monitoring stations? (high confidence) Results depend on low quality monitoring points (low Good status Methodology diagram for confidence) or human impact YES (endangered, low is not proved. chemical groundwater test confidence) No. 1.

FINAL REPORT

Marandi, A., Karro, E., Osjamets, M., Polikarpus, Andres Marandi [email protected] M., Hunt, M. 2020. Eesti põhjaveekogumite sei- Enn Karro [email protected] sund perioodil 2014-2019. EGF 9416. Eesti Geo- Madis Osjamets [email protected] loogiateenistus, Rakvere. The project report can Maile Polikarpus [email protected] be downloaded from the Estonian Geological Marlen Hunt [email protected] Archive at https://fond.egt.ee/fond/egf/9416.

GEOLOGICAL SURVEY OF ESTONIA 2020 33 HYDROGEOLOGY AND ENVIRONMENTAL GEOLOGY

The results of groundwater body (GWB) status assessment and the reliability of the tests. (P) indicates that GWB is under pressure.

Groundwater Body (GWB) number and name Status Confidence Chemical Quantitative 1 Cambrian-Vendian Gdov Good(P) Good Low 2 Cambrian-Vendian Voronka Poor Good High 3 Cambrian-Vendian Good (P) Good (P) High 4 Ordovician-Cambrian in West-Estonian RBD Good (P) Good Low 5a Virumaa Ordovician-Cambrian in East-Estonian RBD Good Good High 5b Tartu Ordovician-Cambrian in East-Estonian RBD Good Good High 6Ida-Viru Ordovician Poor Good Low 7 Ida-Viru Ordovician oilshale basin Poor Poor Low 8 Hiiumaa Silurian-Ordovician Good (P) Good Low 9 Saaremaa Silurian Good (P) Good Low 10 Harju Silurian-Ordovician Good Good Low 11 Matsalu Silurian-Ordovician Poor Good Low 12 Pärnu Silurian-Ordovician Good (P) Good Low 13 Silurian-Ordovician in East-Estonian RBD Good Good Low 14 Pandivere Silurian-Ordovician in West-Estonian RBD Good Good Low 15 Pandivere Silurian-Ordovician in East-Estonian RBD Poor Good Low 16 Adavere-Põltsamaa Silurian-Ordovician Good Good High 17 Silurian-Ordovician beneath Devonian in West-Estonian RBD Good Good High 18 Silurian-Ordovician beneath Devonian in East-Estonian RBD Good Good High 19 Ruhnu Middle-Lower-Devonian Good Good Low 20 Kihnu Middle-Lower-Devonian Good (P) Good Low 21 Middle-Lower-Devonian in West-Estonian RBD Good (P) Good Low 22 Middle-Lower-Devonian in East-Estonian RBD Good Good High 23 Middle Devonian in West-Estonian RBD Good Good Low 24 Middle Devonian in East-Estonian RBD Poor Good Low 25 Middle Devonian in Koiva RBD Good Good High 26 Upper Devonian Good Good High 27 Vasavere Quaternary Poor Poor Low 28 Meltsiveski Quaternary Good (P) Good (P) Low 29 Männiku-Pelguranna Quaternary Good (P) Good Low 31 Prangli Quaternary Poor Good High

34 GEOLOGICAL SURVEY OF ESTONIA 2020 HYDROGEOLOGY AND ENVIRONMENTAL GEOLOGY

Chloride concentrations in the Gdov aquifer. Salinisation of groundwater in Ida-Viru County

Despite localised problems, such as higher ni- also bore seawater from that time. The composition of trate and fluoride concentrations or salinisation of this water began to change over time as the sediments groundwater in coastal regions, groundwater con- became buried, but retained its general salinity and the ditions in Estonia can be said to be relatively good. characteristics pointing to the marine origin of the wa- Nevertheless, the supply of drinking water in Ida-Vi- ter. However, more than a million years ago, when the ru County is becoming a serious problem. The Gdov Earth experienced several ice ages – the last of which aquifer, which has been the main source of drinking released Estonia from its grip a little over 12,000 years water in Ida-Viru County for many years, is becom- ago – significant changes began to occur. The immense ing increasingly saline and in many places no longer weight of the continental glacier, which was a couple of meets EU drinking water standards due to exceed- kilometres thick, pushed the meltwater that had accu- ing chloride content (> 250 mg/l). mulated under the glacier several hundred metres un- derground, into the rocks in which it is held to this day. The formation of the Gdov aquifer began 600 million During these processes, relict saline groundwater (for- years ago, when the first sediments started to accu- merly seawater) was also pushed into the deeper part mulate in the depression in the Earth’s crust that is of the Gdov aquifer. When people eventually learned to now known as the Baltic Sedimentary Basin, which construct deep boreholes, they also began to extract

GEOLOGICAL SURVEY OF ESTONIA 2020 35 HYDROGEOLOGY AND ENVIRONMENTAL GEOLOGY

> 20,000 YEARS AGO TODAY Glacier LOKSA RIGA VILNIUS m amp 0 m amp 0 -200 -200 -400 -400 -600 -600 Gdov -800 aquifer -800 -1000 -1000 -1200 -1200 0 100 200 300 400 500 600 km 0 100 200 300 400 500 600 km

Aquifers Formation of fresh groundwater in the Gdov aquifer Aquitars during ice ages. Crystalline basement Boundary of salt and fresh water groundwater from the Gdov aquifer in Virumaa. Unfor- Direction of fresh groundwater movement Direction of saline groundwater movement tunately, it was not until the late 1980s that it became clear that this fresh groundwater was a relatively lim- ited resource. As freshwater was pumped out, it began, increasingly, to be replaced by saltier groundwater, which, in its chemical composition, is more similar to Värska Mineral Water.

In the course of the LIFE IP CleanEST project, the GSE conducted a study which showed that, while in some areas the salinisation of the water could be reversed by reducing consumption, in Ida-Viru County the pro- cess is largely irreversible. As most of the aquifers have been contaminated during mining operations, the re- maining sources of freshwater only include a few thin and relatively small aquifers and the groundwater in- take constructed in the buried valley of Vasavere. The Salinisation types and intensities in the Gdov aquifer. The red line marks the boundary between areas of reversible latter provides the lion’s share of the water supply for and irreversible salinisation. the Jõhvi region, which, unfortunately, endangers the biota of the Kurtna Lake District. The problem may be solved by building a reservoir in one of the depleted quarries, or we could wait for another ice age.

ELECTRONIC VERSION OF THE INVESTIGATION

https://lifecleanest.ee/sites/default/files/2021-01/Gdovi %20uuring_22.12.2020.pdf

Valle Raidla [email protected] Merle Truu [email protected]

36 GEOLOGICAL SURVEY OF ESTONIA 2020 HYDROGEOLOGY AND ENVIRONMENTAL GEOLOGY

Fieldowork at Kukruse waste rock heap. Photo Siim Tarros. Groundwater survey of Kukruse waste rock heap

Kukruse waste rock heap is one of the many oil shale nine burnt waste rock heaps in Estonia, and most of mining waste rock heaps in Ida-Viru County. Waste the fires took place in the early 1960s. Even though rock heaps consist of limestone that is discard- there have been no open-flame fires recently, the ed during oil shale mining and to a lesser extent of heating processes in the waste rock heaps continue residual oil shale. Heaps of such material are quite to this day (Tamm et al., 2020). In the case of Kukruse inert and do not pose a threat to the environment. waste rock heap, the spread of the pollution into the However, the old deposition technology where the groundwater is complicated by the fact that the waste material was deposited into high heaps with steep rock heap is on top of a mined area. The base of the slopes created favourable conditions for the waste Kukruse oil shale mine workings near the waste rock rock heaps to overheat and ignite. heap is located 10–15 m below ground level.

As a result of overheating, the residual oil shale goes In 2020, the Geological Survey of Estonia conducted through a similar process as in the oil plants – oil shale a groundwater survey in the Kukruse waste rock heap pyrolysis – which emits gases and releases petroleum area. The aim of the survey was to identify whether products. Some of the hazardous substances move the pollutants from the waste rock heap make their through the soil pores and cracks into the ground- way into groundwater and their possible spread into water underneath the heaps. There are a total of drinking water or surface water. The study found

GEOLOGICAL SURVEY OF ESTONIA 2020 37 HYDROGEOLOGY AND ENVIRONMENTAL GEOLOGY

that the groundwater pollution in the im- mediate vicinity of the waste rock heap was moderate. The near-surface Ordovician groundwater in the vicinity of the site ex- ceeds the groundwater quality standard of hazardous substances characteristic of the oil shale industry (Regulation No 39 of the Minister of Environment of 4 September 2019) and has high salinity levels. The con- centration of potassium ions in water can be used as an indicative parameter of the impact of waste rock heaps on the aquatic environment. The concentration of potas- sium ions in the natural hydrological cycle is low. While the potassium concentration of the well 150 m upstream from the edge of the waste rock heap was 16 mg/l, the potas- sium ion concentration of the downstream wells at the edge of the waste rock heap consistently exceeded 2,000 mg/l. At the level of groundwater bodies as groundwater management and quality monitoring units, Kukruse waste rock heap is a source of pol- lution with a local impact. However, since the groundwater outside the waste rock heap disposal site also contains hazardous sub- stances, further monitoring is needed to en- The high concentration of potassium ions in the groundwater in the sure that their content in groundwater does vicinity of the waste rock heap originates from the overheated waste not increase. No extensive spread of pollut- rock. The potassium concentration is high in the survey wells that are ants from the waste rock heap to drinking located downstream and directly at the edge of the waste rock heap. water or rivers through groundwater was identified. Through surveys it was estab- REFERENCES lished that the groundwater flowing below the waste rock heap is flowing in the direc- Regulation No 39 of the Minister of Environment tion of southwest and southwest-south. of 4 September 2019 “Groundwater quality stan- In the direction of groundwater flow, the dards of hazardous substances”. Tamm I, Kesa- nearest and still preserved private well is lo- nurm K, Vainumäe K, Teinemaa E. 2020. Suletud cated 1.4 km from the waste rock heap. No kaevandamisjäätmehoidlate seisukorra hindami- ne (Assessment of the condition of closed mining hazardous substances characteristic of the waste disposal sites). Eesti Keskkonnauuringute oil shale industry were found in the water Keskus OÜ. Tallinn. sample taken from the well.

Madis Osjamets [email protected]

38 GEOLOGICAL SURVEY OF ESTONIA 2020 HYDROGEOLOGY AND ENVIRONMENTAL GEOLOGY

Mõdriku Vanaküla springs. Photo Merle Truu.

The quality of groundwater and surface water in areas with a high proportion of agricultural land

In general, everyone knows that human activities fact that no water body receives its water from a single can aff ect the quality of rivers, lakes and ground- source. Instead, water bodies and groundwater are fed water. Sometimes the negative impact of human by the water in the wider surrounding area. This is called activities can be attributed to a specific pollution the catchment area of the water body. With regard to source (e.g. old industrial sites, wastewater outlets, substances of agricultural origin, all agricultural activi- manure storage). However, often it is not possible ties in the catchment aff ect the quality of water to some to identify a specific source of pollution because the extent. Such an impact is also called diff use pollution. water quality is aff ected by the general land use in the area. That is precisely how agriculture aff ects Fertilisers, pharmaceuticals and pesticides decrease the water bodies. the quality of groundwater and surface water. Fer- tilisers provide nutrients for agricultural land. These In most cases, the deterioration in the quality of the wa- include nitrogen compounds (particularly nitrate and ter bodies and groundwater in an area cannot be attrib- organic nitrogen, together characterised by the to- uted to a specific agricultural producer. This is due to the tal nitrogen indicator) and phosphorus compounds

GEOLOGICAL SURVEY OF ESTONIA 2020 39 HYDROGEOLOGY AND ENVIRONMENTAL GEOLOGY

(particularly phosphate and organic phos- Studied catchments phorus, together characterised by the total River phosphorus indicator). High levels of agricul- Main ditch tural nutrients cause overgrowth in the wa- Fields ter bodies (eutrophication). As a result, the Settlement living conditions there deteriorate (e.g. the oxygen content decreases) and biodiversity diminishes (e.g. some species of fish become extinct in the rivers). In addition, high nitrate levels (more than 50 mg/L) are harmful to the health of humans. Pesticides and their degradation products (e.g. glyphosate and its degradation product aminomethylphos- phonic acid or AMPA) and pharmaceuticals FIGURE 1. The study area and the locations of studied catchments: (e.g. analgesic diclofenac) are toxic to hu- 1 – Vohnja stream; 2 – Kihlevere main ditch; 3 – Põdruse main ditch; mans and nature even in small amounts. 4 – Sõmeru river; 5 – Kunda river; 6 – Pada river. Substances of agricultural origin have a FIGURE 2. SURFACE WATER-HEADWATERS major impact on the natural environment. 10 These account for 60% and 30% of nitrogen 1 8 4 and phosphorus compounds that reach 6 3 Estonian rivers and lakes, respectively. A significant amount of the nutrient load may 4 5 2 6 2 reach surface water bodies via groundwa-

Total-nitrogen Total-nitrogen mgN/L Proportion of agricultural land (%) ter. Furthermore, it is estimated that up 0 20 40 60 80 to 80% of nitrogen compounds and 92% of phosphorus compounds that reach the The average concentration of total nitrogen in the headwaters of the stu- died watercourses in the first monitoring year (2019–2020) and the propor- Baltic Sea are transported through rivers. tion of agricultural land in the catchment. The numbers correspond to the catchments in Figure 1a. The status of the surface water body is considered As part of the LIFE IP CleanEst project, good if its total nitrogen concentration does not exceed 3 mgN/L. funded by the European Union and the Ministry of the Environment of Estonia, FIGURE 3. GROUNDWATER 12 a study of surface water and groundwa- 10 4 ter quality in six catchments in Lääne-Viru 8 6 County will be conducted (Figure 1a). The 1 6 2 participants are the Tallinn University of 4 3 5 Technology, the Geological Survey of Es- 2

Total-nitrogen Total-nitrogen mgN/L Proportion of agricultural land (%) tonia and the Estonian Environmental Re- 020406080search Centre (EKUK). The composition of surface water and groundwater in these The average concentration of total nitrogen in groundwater of the studied catchments in the first monitoring year (2019–2020) and the proportion catchments are monitored over a period of agricultural land in the catchment. The numbers correspond to the of four years between 2019 and 2022. The catchments in Figure 1a. The mentioned nitrate content of 50 mg/L that Geological Survey of Estonia is responsible is harmful to human health corresponds to a total nitrogen content of 11 mgN/L (if the concentration of other nitrogen compounds in groundwater for groundwater surveys. The aim of this is is not significant). to clarify the impact of groundwater on the

40 GEOLOGICAL SURVEY OF ESTONIA 2020 HYDROGEOLOGY AND ENVIRONMENTAL GEOLOGY water quality of surface water bodies and the runoff and groundwater infiltration in- the main natural processes that may alter creased. Higher concentrations of nitrogen the nutrient concentration in groundwater compounds can be found to depths up to before it reaches surface water bodies. The 20–30 meters. In greater depths, nitrogen survey primarily focuses on nutrients of removal processes are already taking place agricultural origin; however, to a lesser ex- in groundwater or the water there is less tent, the concentrations of pesticides and connected to the current hydrological cy- pharmaceuticals are also monitored. cle due to its older age.

The results of the first survey year (2019– Although many of the above patterns were 2020) show, as expected, that higher con- already broadly known, the current ground- centrations of nutrients occur in catch- water survey will help us expand our knowl- ments that have a higher proportion of edge in at least three areas. Firstly, parallel agricultural land (Figure 1b and 1c). The studies of both surface water and ground- concentration of phosphorus compounds water allows us to better explain the role in groundwater is relatively small, and the of groundwater in the formation of surface nitrogen compounds form the greatest water quality. Secondly, the current survey part of the nutrient load. The concentra- enables us to clarify the changes in the com- tion of nitrate in groundwater is high in position of groundwater and surface water some areas (even greater than 50 mg/L) over diff erent seasons and years with diff er- and this has an impact on the quality of ent weather conditions. Thirdly, in addition the surface water. The total nitrogen con- to substances of agricultural origin, the sur- centration in groundwater is also high in vey also examines a variety of other param- some catchments where the same con- eters and substances dissolved in ground- centration in surface water bodies is low water. This makes it possible to determine (Figure 1c). Higher concentrations of nitro- the patterns of groundwater formation and gen compounds occurred in groundwater changes in groundwater quality, as well as and surface water bodies in spring and in the relative age of groundwater as these are winter. The latter is explained by the warm all closely related to the distribution of sub- and wet winter of the survey year when stances of agricultural origin.

Groundwater studies as part of the LIFE IP CleanEst project, activity C10.1

You can read more about the first monitoring year of the study in the electronic report: Iital, A., Kõrgmaa, V., Pachel, K., Roosalu, K., Pärn, J., Osjamets, M., Hunt, M., 2020. LIFE IP CleanEst Joonas Pärn [email protected] activity C10.1 water surveys. Monitoring results. Madis Osjamets [email protected] LIFE IP CleanEst project, Tallinn. https://lifecle- Marlen Hurt [email protected] anest.ee/sites/default/files/2021-01/C10%20 Merle Truu [email protected] Veeuuringute%20aruanne.pdf

GEOLOGICAL SURVEY OF ESTONIA 2020 41 HYDROGEOLOGY AND ENVIRONMENTAL GEOLOGY

Groundwater sampling in Kunda. Cm-V groundwater in northern Estonia is saturated with glacial gases. Photo: Andres Marandi.

Transient 3D modelling of 18O concentrations with the MODFLOW-2005 and MT3DMS codes in a regional-scale aquifer system: an example from the Estonian Artesian Basin

42 GEOLOGICAL SURVEY OF ESTONIA 2020 HYDROGEOLOGY AND ENVIRONMENTAL GEOLOGY

70 71 81 106 131 132 142 150 151 152 153 154 155 158 197 199 118 118 160 161 162 168 90 92 93 145 174 179 180 183 184

38 100 103 104 112 113 114 115 116 117 125 134 148 149 156 157 163 169 194 196 124 73 72 74 84 85 102 102 122 123 135 165 171 75 99 76 198 188 19394 172 87 79 192 91 185 18688 167 146 86 83 166 19014320 17543 98187 89 133 78 44 182 173 120 39159126107 127 101 5824 176 177 63 110 77 128 144 137 31 34 178 18995 164 111 109 140 136 30 23 22 96 80 121 41 49 18 36 3715 147 170 129108 82 52 66 138 132 47 19 51 148 46 65 45 16 42 21 61 57 141 56 60 50 4 62 139 5 6 28 32

26 27 64 59 53

33 54 40 2 68 69 9 10 11 3 25 7 8 55 13 35 195 97 12 48 14 67 6 400 000 6 444 000 6 480 000 6 520 000 6 560 000 6 600 000

360 000 420 000 480 000 540 000 600 000 660 000 720 000 780 000

Tested aquifers

FIGURE 1. 18O testing wells; red solid line – EAB boundary, blue staircase line – HME boundary.

Amounts of natural water containing the heavy This study is based on δ18O measurements in water oxygen isotope 18O vary by up to a few dozen parts from 199 borewells penetrating all major layers of per thousand from the VSMOW standard estab- the Estonian Artesian Basin (EAB). Using the original lished by the International Atomic Energy Agency method, the measured δ18O values were converted in 1968. Above-standard 18O levels (designation: to the corresponding absolute concentrations of 18O δ18O = 1...10‰) are characteristic of water formed in (Figure 2). This conversion made it possible to model tropical climates (the Dead Sea, the Red Sea, etc.). the transient spatial (3D) distribution of 18O in the EAB, Meanwhile, a relatively lower 18O content is charac- which is a multi-layered basin with heterogeneous teristic of modern precipitation (δ18O = -8...-12‰) filtration conditions, using the MODFLOW-2005 and and Arctic ice meltwater (δ18O = -18...-24‰). These MT3DMS codes. The conducted computer experi- variances provide a basis for the reconstruction of ment showed the modelling results to be suffi ciently 18 groundwater formation conditions at δ O determi- accurate. nation points. To demonstrate the practical applicability of the developed 3D computational methodology, eight

GEOLOGICAL SURVEY OF ESTONIA 2020 43 HYDROGEOLOGY AND ENVIRONMENTAL GEOLOGY

18O content and groundwater genetic types 1 22,0...20,0 formation of continental ice over the northwestern part of the EAB 2 20,0...18,0 formation of continental ice over the entirety of the EAB 3 18,0...14,7 thinning of the continental ice due to melting 4 14,7...12,0 gradual disappearance of the ice cover from over the EAB 18O absolute concentration (mg/L) 5 12,0...10,3 formation of the Baltic Ice Lake 6 10,3... 5,0 development of the Baltic Sea 18 FIGURE 2. Genetic types of groundwater according to O during the Holocene content; A/B – EAB water from before the start of continental 7 5,0... 0,1 formation of the modern relief glaciation, G – continental ice meltwater, M – water from preci- of the EAB pitation, AB/AG/BG/GM – mixed water. 8 0,1... 0 intensive use of the groundwa- ter

The geometrical and filtration parameters of the sequential models were given according to the Hydrogeological Model of Estonia (HME) created by L. Vallner in 2002 and later verified through the solving of practical problems. The initial groundwater pressure and the initial ab- solute concentration of 18O were defined for se- quential model No. 1 based on data from previ- ously published research. After the completion of the calculations performed with sequential model No. 1, the obtained results were input to sequential model No. 2 and so on, until the whole series of calculations was completed with FIGURE 3. Groundwater pressure (abs. elevation in m, yellow the 8th model. This yielded an integrated sys- 18 isolines), directions of flow (white arrows), δ O (‰, black das- tem of groundwater flow and transport mod- hed isolines) and genetic types of groundwater, separated by els for the EAB, which was used to reconstruct black solid lines, in Cm-V layers 18 ka before the present. and interpret the history of the geohydrological development of the EAB over the last 22,000 years in the Late Pleistocene and the Holocene.

The modelling proved that, during the time of the last continental glaciation, the meltwater result- ing from frictional heating under the ice sheet functionally interlinked sequential mod- began to penetrate the upper layers of the EAB els of the EAB were created using MOD- transversely and the lower layers laterally from FLOW-2005 and MT3DMS, covering the the depression of the Baltic Sea. This created following time periods (millennia before the various mixes of ice water and the groundwater present) and the corresponding geomor- previously present in the EAB (Figure 2). As the phological and geohydrological processes: continental ice receded, the groundwater began

44 GEOLOGICAL SURVEY OF ESTONIA 2020 HYDROGEOLOGY AND ENVIRONMENTAL GEOLOGY to again be replenished by precipitation, and wa- ter from the expanded Baltic Sea also intruded into the layers. The modelling showed the direc- tion, velocity, and amount of water flows in these processes, as well as how 18O concentrations changed (Figures 3 to 5). Absolute elevation (m) There was a strong correlation between the absolute concentrations measured in the groundwater and the corresponding calculated absolute concentrations of 18O (correlation co- effi cient: 0.86). This indicated that the hydro- geological parameters of the aquifer system input to the sequential models were suffi ciently accurate and that the whole modelling concept FIGURE 4. Hydrogeological situation in vertical cross-section as implemented was correct. A-B of the EAB 18 ka before the present. The 8th sequential model created and verified in the course of the research is a complex flow and transport model of the EAB, which can be used to analyse anthropogenic impacts that have already occurred in the aquatic environ- ment, as well as to predict its future conditions.

The present study is novel because the tran- sient 3D distribution of 18O concentrations in a regional-scale system has not previously been modelled in detail.

RELATED ARTICLE

Vallner, L.; Ivask, J.; Marandi, A.; Vaikmäe, R.; Raidla, V., Raukas, A. Transient 3D simulation of 18O concent- ration by codes MODFLOW-2005 and MT3DMS in a FIGURE 5. Modern hydrogeological situation in Cm-V layers; regional-scale aquifer system: an example from the yellow and light blue isolines – groundwater pressure (abs. Estonian elevation in m) in 1910 and 2016, respectively. The coordinates in the figures are given in metres according to the L-EST97 system. Artesian Basin. Estonian Journal of Earth Sciences, 2020, 69, 3, 154–175. https://doi.org/10.3176/earth. 2020.11.

PhD Jüri Ivask [email protected] PhD Andres Marandi [email protected] PhD Valle Raidla [email protected] PhD Anto Raukas [email protected] PhD Rein Vaikmäe [email protected] PhD Leo Vallner Leo.Vallner@ taltech.ee

GEOLOGICAL SURVEY OF ESTONIA 2020 45 HYDROGEOLOGY AND ENVIRONMENTAL GEOLOGY

Students Elina Kuusma and Markus Kivimägi filling RM-2 flasks with soil air. At the same time, the red Markus 10 is pumping air from the soil pores into its ionization chamber. Photo: Krista Täht-Kok.

Radon research in insuffi ciently studied municipalities: Keila and Võru towns, Rõuge, Setomaa, Võru, and Ruhnu rural municipalities

Radon research regarding radon risk. There were 19 insuf- ficiently studied municipalities at the start In 2019 and 2020, radon research carried of the current research, and by the end of it out by the Geological Survey of Estonia their number had declined to 13. focused in such municipalities that are designated as priority II by the Ministry of Estonia adopted the Regulation No. the Environment, i.e., insuffi ciently studied 28, “Reference levels for indoor radon

46 GEOLOGICAL SURVEY OF ESTONIA 2020 HYDROGEOLOGY AND ENVIRONMENTAL GEOLOGY concentration in workrooms; the proce- The Geological Survey of Estonia used pre- dure for radon measurements and obliga- vious soil air radon surveys for classifying tions of employers at workplaces with an the administrative units. Soil air surveys have increased radon risk” (RT I, 03.08.2018, 4) been conducted in Estonia for almost 20 in the year 2018. This regulation requires years, which provided material for the pub- that the annual average radon activity con- lication of the Estonian Soil Radon Risk and centration in premises must not exceed Radiation Atlas in 2017 (Petersell et al., 2017). 300 Bq/m³. Regulation No. 28 implements the EU Council Directive 2013/59/Eur- The studied Rn soil levels are also related atom (BSS, 2013), laying down basic safety to the geological and geomorphological standards of protecting against dangers structure of the ground. Soil or ground arising from exposure to ionising radiation. properties and their measurements are On the basis of the Regulation No. 28, the more reliable and predictable in compari- Estonian administrative units were catego- son with indoor air measurements, which rised and prioritised using data from previ- reflect varying construction requirements. ous radon surveys: As a working hypothesis, an Rn activity concentration of 75 kBq/m³ in soil air corre- ■ Priority I administrative units with a high sponds to the indoor reference limit of 300 potential radon risk; kBq/m³, which is derived from the adminis- ■ Priority II administrative units, i.e., areas trative implementation of the abovemen- with the need of additional research; tioned Regulation No. 28.

■ Priority III administrative units with a As a result, the studied towns and rural mu- medium or low potential radon risk. nicipalities were categorised as follows:

Emanometer Markus 10 and the sequence of Rn concentrations measured with the Rn meter RM-2.

GEOLOGICAL SURVEY OF ESTONIA 2020 47 HYDROGEOLOGY AND ENVIRONMENTAL GEOLOGY

High estimated Rn-risk Information incomplete Low or average Rn-risk

Rn risk map of Estonian administrative units in 2020.

■ The Keila town and the Setomaa and rect method, which calculates the potential Võru rural municipalities turned out to Rn content in the soil, using eU, i.e., uranium be Priority I in equilibrium with the naturally occurring radium in the soil. The other two methods ■ The Võru town and the Rõuge and Ruh- measure the Rn content in soil air directly. nu rural municipalities turned out to be Priority III The Geological Survey of Estonia per- formed simultaneous measurements at 145 Comparison of the methods used in the study points using these three methods. Geological Survey of Estonia The potential Rn activity concentration in soil was determined indirectly with the During 2019 and 2020, the Geological Sur- gamma spectrometer GT-40, and directly vey of Estonia has been using three radon with the emanometer Markus 10 and the survey methods in parallel. One is an indi- RM-2 equipment.

48 GEOLOGICAL SURVEY OF ESTONIA 2020 HYDROGEOLOGY AND ENVIRONMENTAL GEOLOGY

The two direct measurement methods 10% more efficient. It is often not possi- provided results in 125 of the 145 analysed ble to measure radon with the Markus study points, i.e., in 86% of the cases. Since 10 emanometer in silty soil or fine sand, the two direct measurement methods did whereas the RM-2 equipment does not not work particularly well in moist or clayey always function conveniently on alvars, soil, it proved to be challenging to perform i.e. limestone plains with thin or no soil, further analyses, as gas does not circulate or in situations where the topsoil layer well under such conditions. is very thin. And similarly to Markus 10, sometimes the RM-2 equipment mal- Of the two direct methods, the radon functions when used on fine sand. measurement system RM-2 proved to be

REFERENCES

Basic Safety Standards (BSS) Directive. Council Petersell, V., Karimov, M., Täht-Kok, K., Shto- Directive 2013/59/Euratom of 5 December 2013. kalenko, M., Nirgi, S., Saarik, K., Milvek, H. 2017. http://data.europa.eu/eli/dir/2013/59/oj – seen Eesti pinnase radooniriski ja looduskiirguse at- 20.01.2021. las. The Atlas of Radon Risk and Natural Radia- tion in Estonian Soil. Geological Survey of Esto- Regulation of Minister of the Environment nia. Tallinn, 89. 06.08.2018 No. 28 “Reference levels for indoor radon concentration in workrooms, the proce- https://www.envir.ee/sites/default/files/eesti_ dure for radon measurements and obligations rn_atlas_2017_kyljendatud.pdf – seen 20.01.2021. of employers at workplaces with an increased radon risk” adopted in Estonia in 2018 (RT I, 03.08.2018, 4).

Krista Täht-Kok [email protected] Elina Kuusma [email protected]

GEOLOGICAL SURVEY OF ESTONIA 2020 49 HYDROGEOLOGY AND ENVIRONMENTAL GEOLOGY

Recharge area

Discharge area

Spring

Spring mire

Water table

Unconfined aquifer

Confining bed

Confined aquifer

GroundEco – joint management of groundwater dependent ecosystems in transboundary Gauja–Koiva river basin

From 2018 to 2020, the Geological Survey of Estonia water system. At the same time, managing the trans- participated in the Estonian-Latvian collaborative boundary river basin is necessary due to the geo- project ‘Joint management of groundwater depend- logical and hydrological conditions as well as the EU ent ecosystems in transboundary Gauja–Koiva river Water Framework Directive (2000/60/EC), which basin’, or GroundEco. is binding to both countries. When the project was first launched, Latvian research institutions lacked a The border between Estonia and Latvia divides the methodology for identifying and classifying ground- Gauja–Koiva river basin administratively into two water-dependent terrestrial ecosystems (GDTEs), areas sharing a common groundwater and surface and one of the main objectives of the project was

50 GEOLOGICAL SURVEY OF ESTONIA 2020 HYDROGEOLOGY AND ENVIRONMENTAL GEOLOGY

Layout plan and monitoring network of the Matsi Pilot Area. to develop a common methodology that (water chemistry) assessment schemes would be suitable for the natural conditions for determining whether the condition of of both Estonia and Latvia and that would the groundwater is damaging GDTEs and, if enable joint management of terrestrial necessary, for planning remedial measures ecosystems on both sides of the border. for GDTEs that are in poor condition.

The data required for the development of As a result of the research, 60 GDTEs with a the methodology was collected from se- total area of approx. 732 ha (nearly 2/3 of the lected pilot areas in both Estonia and Latvia. area of the island of Ruhnu) were identified in Conceptual models were developed for the the Gauja–Koiva transboundary river basin. pilot areas, and the results of the research In the future, the methodology is planned to were used to validate the methodology. be utilised for the preparation of the third The selected pilot areas were the Matsi cycle (2022–2027) of river basin water man- Spring Fen in Rõuge Parish, Võru County, agement plans, which will ensure the long- Estonia and Kazu leja in Priekuļi Municipal- term protection of common groundwater ity, Latvia. The methodology also includes resources (as the main source of potable quantitative (water level) and qualitative water) and the related ecosystems.

GEOLOGICAL SURVEY OF ESTONIA 2020 51 HYDROGEOLOGY AND ENVIRONMENTAL GEOLOGY

Middle Devonian groundwater body in the Gauja-Koiva River basin

D2gj aquifer contributes on average 67% to the Q aquifer contributes on average 33% to the recharge of the spring fen M1 polygon. recharge of the spring fen M1 polygon. Characteristics Characteristics Artesian/anoxic Unconfined/oxic Stable thermal and isotope signatures Unsteady thermal and isotope signatures Higher TDS (462±35 mg/l) Lower TDS (287±74 mg/l) Longer residence time Shorter residence tima 2+ 2+ + 2- - - - Higher DIC, BA , Sr , Fetot ja SiO2 Higher DOC, Ntot, Ptot, K , SO4 , F , Cl , Br ja Al3+

arable land dug well Glaciolacustrine 90 m and glaciofluvial Elevation (masl) Q interflow sediments Matsi spring fen M1 polygon Q baseflow 80 (confining layer) Glacial sediments low nutrient load high aquifer Q Gauja formation pristine fen status disturbed sandstone 70 potentiometric surface Peat Mustjõgi river Tufa 60 peat

Spring tufa aquifer gj-ar 2

Distance m200200300 400 500 600 700800 900 1000 1100 1200 1300 1400 1500 1600 D

Conceptual hydrogeological model of the Matsi Pilot Area.

GROUNDECO PARTNERS AUTHORS OF THE GROUNDECO FINAL REPORT

Latvian Centre for Environment, Geology, and Meteorology, Tallinn Uni- Retike, I. (1,3), Kalvāns, A. (3), Priede, A. (5), Tarros, versity, Institute of Ecology, University of Latvia, Faculty of Geography S. (7), Terasmaa, J. (2), Türk, K. (4), Bikše, J. (3), De- and Earth Sciences, Ministry of the Environment of the Republic of Es- midko, J. (1), Koit, O. (2), Küttim, M. (2), Lode, E. (2), tonia, Nature Conservation Agency of Latvia, Vidzeme Planning Region, Pärn, J. (2), Popovs, K. (3), Vainu, M. (2), Valters, Geological Survey of Estonia K. (1), Abreldaal, P. (2), Babre, A. (3), Bīviņa, I. (6), Caune, K. (1), Marandi, A. (7), Polikarpus, M. (7), Raidla, V. (7), Rieksta, M. (6), Sisask, K. (2)

The full project report in English (incl. the deve- loped methodology, pilot studies, and sugges- tions) can be downloaded from the Estonian Geological Archive: https://fond.egt.ee/fond/ egf/9446

Andres Marandi [email protected] Siim Tarros [email protected]

52 GEOLOGICAL SURVEY OF ESTONIA 2020 MARINE GEOLOGY

Alliklepa monitoring area. Photo Sten Suuroja.

Coastal monitoring in 2019-2020

The Geological Survey of Estonia per- itoring program. The purpose of mon- formed coastal monitoring under an itoring is to observe coastal processes agreement with the Environmental Agen- (erosion and accumulation) generated by cy in 2019–2020. At the end of 2020, a natural and anthropogenic factors and comprehensive report was completed. to clarify trends of coastal development. The results and data collected during the Monitoring unfolds possible development monitoring work as well as various the- of diff erent coastal areas (necessary for matic GIS maps were uploaded to the en- construction of ports, buildings, roads, vironmental monitoring database KESE recreational planning) and provides a pre- (https://kese.envir.ee/kese). diction of the development of coastal ar- eas. The monitoring areas were selected Coastal monitoring started in 1994 as a to cover areas of diff erent geology and hy- part of the national environmental mon- drodynamic conditions.

GEOLOGICAL SURVEY OF ESTONIA 2020 53 MARINE GEOLOGY

Map of monitoring areas of the coastal monitoring program in 2019–2020.

Given the growing need for coastal ge- This combined methodology permits to ological data and based on the tasks collect data much more effi ciently, over a and needs arising from European Union larger area and volume, and to observe the directives, current coastal monitoring processes taking place in the coastal zone methodology was significantly improved in areas of abrasion and accumulation. within this study. In addition to land- based elevation profiles using RTK-GPS On the basis of data collected during mon- up to the depth of 1.5 m, surveying of the itoring: nearshore zone to the depth of 10 m along ■ digital monitoring profiles were compi- underwater beach slopes was performed led and compared with data of previous in pre-selected monitoring areas. The years to analyze and describe changes underwater part of the monitoring areas in the coastal zone was surveyed using a geophysical seabed profiling complex consisting of several ■ thematic maps of monitoring areas seabed profilers with different operating were composed: maps of bathymetry, frequencies (Boomer, Chirp, Sparker), as bottom sediments and lithodynamics, well as a side-scan sonar system for de- indicating the areas of abrasion and termining the distribution and composi- accumulation, sediment movement and tion of sediments. areas of anthropogenic impact.

54 GEOLOGICAL SURVEY OF ESTONIA 2020 MARINE GEOLOGY

Thematic maps of the Naissaare monitoring area: bathymetric map, mosaic image of the side-scan sonar profiles, map of bottom sediments and lithodynamics.

Thematic maps and data models based on out for the first time in seven monitoring geophysical surveying data for coastal ar- areas (Harilaiu, Järve-Mändjala, Kakumäe, eas allow making more eff ective decisions Naissaare (port), Narva-Jõesuu, Tareste for long-term planning of coastal and ma- and Valgeranna). The criteria for the selec- rine areas in order to prevent risks asso- tion of underwater coastal slope surveying ciated with coastal and marine use (incl. areas was need-based: port congestion coastal erosion, aggradation of ports and (Narva-Jõesuu, Tareste, Naissaare), and waterways, etc.). areas with active sediment movement (Ka- kumäe, Järve-Mändjala). RTK-GPS elevation profiles were measured in 11 monitoring areas in the course of the In addition, a review of all Estonian moni- study: Aegna, Harilaiu, Järve-Mändjala, toring areas was carried out to assess and Kakumäe, Naissaare (port), Narva-Jõesuu, identify possible future trends (human ac- Pirita, Ruhnu, Tahkuna, Tareste and Valge- tivities, sediment movement, port conges- ranna. In addition, a geophysical survey of tion, erosion, accumulation) of every mon- the underwater coastal slope was carried itoring area.

Anu Veski [email protected] Sten Suuroja [email protected] Martin Liira [email protected] Igor Tuuling [email protected]

GEOLOGICAL SURVEY OF ESTONIA 2020 55 MARINE GEOLOGY

Profiling in Kuivarahu canal. Photo S. Suuroja.

Geophysical surveys of fairways

The geophysical research methods used to study As part of the geological mapping of Väinameri Sea the fairways provide basic relevant data on the sea- in 2020, geological surveys were conducted on the bed geology of the fairways that require dredging. following fairways that require dredging:

1. Sviby canal; 2. Kuivarahu canal; 3. Väinameri Sea fairway in the direction of Kesse; 4. Saareotsa canal.

Sub-bottom profilers with diff erent frequency ranges and a side-scan sonar were used for the geophysical surveys. The survey provided information about the canals and the types of sediments in the vicinity as well as their lithological composition, range and thickness.

56 GEOLOGICAL SURVEY OF ESTONIA 2020 MARINE GEOLOGY

Sub-bottom profiler Chirp interpreted profile of Kuivarahu ridge area trending southwest to northeast.

The resulting seabed geomorphology plan the lithodynamics of sediments for and sediment surface distribution data- the construction and maintenance of ca- set and the interpreted seismoacoustic nals, including the erosion of the seabed cross-sections can be used as a necessary caused by currents and ships’ propellers. and reliable base material for the con- This is especially important for canals that struction and reconstruction of navigable are dredged in moraine or glaciofluvial canals. In addition, the composition and sediments as there is a risk of coarse de- distribution of sediments can be used to bris accumulation in the canal.

Locations of the profiles on the Vormsi and Kuivarahu fairways.

Anu Veski [email protected] Sten Suuroja [email protected]

GEOLOGICAL SURVEY OF ESTONIA 2020 57 MARINE GEOLOGY

Fieldwork on the research ship “Salme” in September 2020. Photo Martin Liira. Environmental status of seabed sediments in the Baltic Sea

To clarify the environmental status of Estonian marine sed- has relatively little water exchange with iments and develop the necessary methodology for assess- the Atlantic Ocean. The catchment area, ing the state of the environment, the Geological Survey of or the area from which water flows into the Estonia implements the project “Development and imple- Baltic Sea, is about 1.7 million km², which is mentation of a methodology for assessing the status of sea- more than four times the Baltic Sea area bed sediments” (2020–2022). The impact of this project is and home to almost 85 million people. Our directly aimed at improving the environmental condition of home sea is characterized by several gra- the seabed. As a result of the project, the methodology for dients: biodiversity, species composition, assessing the state of the marine environment and the nec- and the gradual change in water temper- essary source data will be supplemented. ature and salinity from south to north. Bi- odiversity is generally low throughout the The current Baltic Sea is a geologically Baltic Sea, and many organisms live close young, semi-enclosed brackish sea con- to their level of tolerance. The above char- nected to the North Sea through narrow acteristics make the Baltic Sea ecosystem Danish straits through which the Baltic Sea particularly sensitive to environmental

58 GEOLOGICAL SURVEY OF ESTONIA 2020 MARINE GEOLOGY impact. Eutrophication is considered to be the most severe environmental problem in the Baltic Sea.

Eutrophication of the Baltic Sea is caused by en- richment of the water body with anthropogenic nutrients. During the 20th century, nitrogen input to the Baltic Sea has tripled, and phosphorus input has increased fivefold. As awareness of harmful in- fluence of eutrophication has increased, nitrogen emission into the Baltic Sea has decreased by 16% and phosphorus emission by 18% between 1994 and 2010. Nevertheless, water quality has not improved as expected, meaning that the concentrations of nu- trients have not decreased. As a result of extensive nutrient uptake over the past decades, phosphorus has accumulated in seabed sediments, from which it is gradually released back into the water. This phe- nomenon is called internal phosphorus loading. Many factors are involved in releasing phosphorus from sediments, but the most significant eff ect is the low dissolved oxygen content of seawater – hypoxia. Location of the sampling stations in the Gulf of Finland, Hypoxia (defined as the oxygen content of ground- Väinameri Sea, strait of Suur väin, and Gulf of Riga. water below 2 mg/l) is a growing problem worldwide, and since the 1960s, the so-called “dead zones” in Within this research project framework, the state of coastal seas have expanded. Hypoxia is also a com- the seabed environment of Estonian coastal waters mon phenomenon in the Baltic Sea. Such low oxygen is assessed by moving from the estuary of the Gulf concentrations in seawater impair the resilience of of Finland across the Väinameri Sea region to the the ecosystem and aff ect the rate of nitrogen and northern part of the Gulf of Riga. As a result of this phosphorus release from sediments. Phosphorus work, the methodology and baseline data (incl. map accumulated in seabed sediments can exist in sev- layers) will be compiled, which are necessary for the eral diff erent forms. Only some of them are mobile, development of quantitative indicators and assess- i.e. they can move back into the seawater and cause ment methods for the Estonian sea area and the eutrophication. Hypothetically, there may be a situ- establishment of an updated (monitoring) method- ation in sediments where there is a lot of phosphorus. ology for systematic surveying of monitoring areas. Still, it is all in a non-mobile form, i.e. it is trapped in In September 2020, a sea voyage with the research the sediment and does not cause additional eutroph- vessel “Salme” took place within the framework of ication. However, as a rule, part of the phosphorus is this project, during which sediment materials were always in a mobile form, but there is no correspond- collected from sampling stations, and preparations ing data regarding the Estonian seabed. were made for the analytical program.

Martin Liira [email protected]

GEOLOGICAL SURVEY OF ESTONIA 2020 59 MARINE GEOLOGY

Kesselaid with Kesse cliff Püssinina cliff on the Muhu island

A view to the strait of Suur väin from the Püssina cliff on the island of Muhu. Nothing reveals that the greatest bedrock depths (~ 40 m b.s.l.) of the Suur väin occur in its northern part, where the islet of Kesselaid rises to nearly 15 m a.s.l. Nu- merous bedrock cliff s (sections of the Silurian Klint) suggest that underlying the Suur väin a bedrock valley was possibly formed in erosion caused by Cainozoic rivers and Pleistocene glaciation. Photo I. Tuuling.

The strait of Suur väin between the Estonian mainland and the Muhu Island overlies a complex bedrock valley

About ten years ago it was hard to imagine that Geological mapping in the shallow sea became pos- widespread marine geological mapping of the Es- sible after having a research vessel equipped with tonian nearshore areas could be possible. Now, diff erent seismo-acoustic profilers (Pinger, Chirp, when the Geological Survey of Estonia has finished Boomer) and a side-scan sonar for studying bottom mapping within the strait of Suur väin, we have sediments, relief and morphology. much higher confidence in continuing with map- ping of the Estonian marine areas. In 2019, our mapping team covered the area with a regular net of the seismo-acoustic lines 1 km (in places even 0.5 km) apart. Only the boomer impulse penetrated the glacial till (after changing the signal

60 GEOLOGICAL SURVEY OF ESTONIA 2020 MARINE GEOLOGY settings during interpretation) and revealed the complete Quaternary sequence with the bedrock surface. After interpretation of the seismo-acoustic data, Quaternary and bedrock relief maps were composed for the strait. Combining the attitudes of the bed- rock layers with the bedrock relief made it possible to outline the outcropping Silurian stages beneath the strait.

One of the most important results of our mapping project was contouring for the first time the bedrock relief of the Suur väin area. The bedrock relief map reveals a complex valley that joins the Gulf of The research vessel at the Kuivastu harbour. Riga with the Väinameri Sea. The general A chirp profiler on the portside of the vessel. roughness and depth values of the bed- Photo S. Suuroja. rock surface increase towards Väinameri. Thus, two channels where the bedrock bedrock surface regularly rises towards relief drops 30-40 m b.s.l. occur in the the southern part of the strait, where the northern part of the strait, whereas the depth and width values of the overlying bedrock surface on the Kesselaid islet be- channels are waning, and the extent of the tween them rises to nearly 15 m a.s.l. The mainland bordering plateaus is increasing.

W E

Glacio-fluvial esker Littorina sediments

Surface of glacial till Baltic Ice Lake, Yoldia Sea and Ancylus Lake (varved clays)

Main channel of the Suur Strait Kesselaid elevation Uisu channel

Glacio-fluvial esker Littorina sediments

Bedrock Baltic Ice Lake, Yoldia Sea and Bedrock Glacial till Ancylus Lake (varved clays)

A nearby seismo-acoustic profile (Boomer) to the south of the Kesselaid islet shows diff erent in- formation and interpretation possibilities after changing the settings of impulse parameters. The profile also reveals the main bedrock relief units in the northern part of the strait.

GEOLOGICAL SURVEY OF ESTONIA 2020 61 MARINE GEOLOGY

Only the channel nearby the Muhu Is- land extends all across the strait. A similar bedrock background suggests that this complex bedrock valley formed through combined erosion caused by Cainozoic rivers and Pleistocene glaciers. There is a suggestion that the Soela strait between the Hiiumaa and Saaremaa islands is alleg- edly overlying the extension of the Kasari Preglacial valley bordered from the south with the Silurian Klint. Therefore, we may 0–10 m consider the strait of Suur väin as a so- 10–15 m called “klint bay”, analogic to bays formed 15–25 m along the North Estonian Klint. This idea 25–30 m is supported by numerous Silurian cliff s

30–40 m (e.g. Kesse, Püssina and Üügu) occurring around the northern part of the strait. > 40 m Further mapping of Väinameri will answer if this suggestion is watertight or not. Map of thickness of the Quaternary deposits. The map of the thickness of Quaternary deposits confirms that sediment trans- port in the strait occurs prevailingly in the south-north direction (towards Väinameri) following the movement of the water col- umn in the strait, induced by the governing wind direction. As a result, sediments have 0 kuni -10 m gradually been filling up the bedrock de- 0 kuni -20 m pressions surrounding Kesselaid. Speeding

<- 30 m up of the bottom current causes thinning of the sedimentary cover in the narrow- Depending on the location the est part of Suur väin between the islands height value can of Kesselaid and Muhu. The water column vary between -10 up to -30 m there is figuratively pushed through a bot- tleneck. This bottleneck area is expressed as the deepest (26 m b.s.l.) channel-like section in the bathymetry, where the sea Bedrock relief map of Suur väin with depths are 5–10 m more than in the sur- distinguished main units. rounding areas due to erosion.

Igor Tuuling [email protected] Sten Suuroja [email protected] Anu Veski [email protected]

62 EESTI GEOLOOGIATEENISTUS 2020

GEOLOGICAL SURVEY OF ESTONIA YEARBOOK 2020

RAKVERE 2021