Joonas Virtasalo

Geological Survey of Finland | GTK · Marine Geology

This paper shows a numerical replication of a laboratory-scale free fall cone penetrometer test of marine clay. The numerical simulation involves large deformations and considers the destructuration of clay, strain rate effects, and non-linear material behaviour. The numerical simulation well replicates the laboratory experiment captured on a high-...

The paper presents experimental results of investigations of offshore deposits from the Gulf of Finland in the Baltic Sea. Firstly, it briefly reviews the sedimentary history of the studied site. Then, it presents results from marine geological investigations, including seismoacoustic reflection sub-bottom profiles and long sediment cores collected...

Hadal trenches are unique geological and ecological systems located along subduction zones. Earthquake-triggered turbidites act as efficient transport pathways of organic carbon (OC), yet remineralization and transformation of OC in these systems are not comprehensively understood. Here we measure concentrations and stable- and radiocarbon isotope...

The construction of wind energy and related infrastructure in offshore areas in Finland is rapidly increasing. Seabed properties play a key role in designing offshore structures. Marine geological survey methods and sediment coring are often used for preliminary seafloor characterization. In addition, the in situ free fall cone penetrometer (FF-CPT...

Flocculation of riverine dissolved organic matter to the particulate form in estuaries is an important mechanism for capturing dissolved metals to newly formed organic particles, regulating the metal transport from land to sea. The process is particularly relevant for rivers draining boreal acid sulfate soils of western Finland, which are known to...

The paper shows a numerical simulation of a fall cone test done on a soft and sensitive marine clay sample collected from the Gulf of Finland in the Baltic Sea. The simulation involves large deformations and takes into account the destructuration of clay, strain rate effects, and non-linear material behaviour. First, the analysed fall cone test was...

Flocculation of riverine dissolved organic matter to the particulate form in estuaries is an important mechanism for capturing dissolved metals to newly formed organic particles, regulating the metal transport to the sea. The process is particularly relevant for rivers draining boreal acid sulphate soils of western Finland, which are known to deliv...

Glacial landforms provide invaluable information on the dynamics and extent of past ice sheets. In planform view, murtoos are triangular-shaped subglacial landforms that have recently been described from areas previously covered by the Fennoscandian Ice Sheet and whose formation has been linked to meltwater activity. We document the first occurrenc...

For millennia, humans have gravitated towards coastlines for their resource potential and as geopolitical centres for global trade. A basic requirement ensuring water security for coastal communities relies on a delicate balance between the supply and demand of potable water. The interaction between freshwater and saltwater in coastal settings is,...

Sedimentary molybdenum (Mo) and uranium (U) enrichments are widely used to reconstruct changes in bottom water oxygen conditions in aquatic environments. Until now, most studies using Mo and U have focused on restricted suboxic-euxinic basins and continental margin oxygen minimum zones (OMZs), leaving mildly reducing and oxic (but eutrophic) coasta...

This study investigated the behavior of 87Sr/86Sr, δ7Li and δ34S in the STE and three seafloor pockmarks with different degrees of groundwater influence, as constrained based on δ2H and δ18O, at the Hanko SGD site in Finland, in the northern Baltic Sea. These data were supplemented by groundwater and seawater measurements.

For millennia humans have gravitated towards coastlines for their resource potential and as geopolitical centres for global trade. A basic requirement ensuring water security for coastal communities relies on a delicate balance between the supply and demand of potable water. The interaction between freshwater and saltwater in coastal settings is, t...

The impact of submarine groundwater discharge (SGD) on coastal sea biogeochemistry has been demonstrated in many recent studies. However, only a few studies have integrated biogeochemical and microbiological analyses, especially at sites with pockmarks of different degrees of groundwater influence. This study investigated biogeochemical processes a...

Multiple biogeochemical processes in estuaries modulate the flux of nutrients from land to sea, thus contributing to the coastal filter. The role of particle dynamics in regulating the fate of terrestrial nutrients in estuaries is poorly constrained. To address this issue, we resolved the particle size distribution of suspended material, and quanti...

Anthropogenic radionuclides are among those human impacts, which can be seen widely in the marine and terrestrial ecosystems. Fallout from the 1986 Chernobyl nuclear power plant accident has rendered the Baltic Sea as the most polluted marine body in the world with respect to ¹³⁷Cs. This research investigated sediment cores from 56 sites around the...

Understanding the local stratigraphy and geometry of sediment units is necessary for successful 3D modelling and the prediction of ground behaviour and engineering-geological properties for urban land use and construction. A detailed 3D model of the main sediment units for the Rastaala basin in southern coastal Finland was constructed, combining a...

During the last glacial period, the western sea area of Estonia in the northern Baltic Sea was covered by the Fennoscandian continental ice sheet. High-resolution multibeam bathymetric images of the seafloor reveal widespread linear and curved depressions, interpreted as iceberg scours (ploughmarks) that were produced by ploughing and grounding ice...

The emergence of digital map processing and interpretation environments, including advanced tools for 3D modelling and forward modelling, has created a demand for easy access to well-organized geological map data. At the same time, the interpretation of LiDAR DEM imagery with high spatial resolution has revolutionized the production of new Quaterna...

Three-dimensional geological and groundwater flow models of a submarine groundwater discharge (SGD) site at Hanko (Finland), in the northern Baltic Sea, have been developed to provide a geological framework and a tool for the estimation of SGD rates into the coastal sea. The dataset used consists of gravimetric, ground-penetrating radar and shallow...

Rivers draining the acid sulfate soils of western Finland are known to deliver large amounts of trace metals with detrimental environmental consequences to the recipient estuaries in the eastern Gulf of Bothnia, northern Baltic Sea. However, the distribution of these metals in the coastal sea area and the relevant metal transport mechanisms have be...

Pyrite-δ³⁴S and -δ⁵⁶Fe isotopes represent highly sensitive diagnostic paleoenvironmental proxies that express high variability at the bed (< 10 mm) scale that has so far defied explanation by a single formative process. This study reveals for the first time the paleoenvironmental context of exceptionally enriched pyrite-δ³⁴S and -δ⁵⁶Fe in bioturbat...

The concentrations, loads and speciation of rare earth elements (REEs) were studied in a 3.5 m thick mud depositional succession from an estuary in the Gulf of Bothnia. The uppermost 182.5 cm of the mud, estimated to have deposited from the early 1970s to 2011 (sampling year), had very high REE concentrations (596−1456 ppm) and accumulation rates (...

Molybdenum (Mo) and uranium (U) contents in sedimentary archives are often used to reconstruct past changes in seafloor oxygenation. However, their sequestration processes are as yet poorly constrained in low-salinity coastal waters, which often suffer from anthropogenic eutrophication but only mild oxygen depletion. Due to the consequent lack of r...

Rivers draining the acid sulphate soils of western Finland are known to deliver large amounts of trace metals with detrimental environmental consequences to the recipient estuaries in the eastern Gulf of Bothnia, northern Baltic Sea. However, the distribution of these metals in the coastal sea area, and the relevant metal transport mechanisms have...

Natural and anthropogenic sediment mixing can significantly impact the fidelity of sedimentary records of climate and environmental variability and human impact. This can lead to incorrect interpretations of the previous state(s) of a given ecosystem, its forcing mechanisms, and its future development. Here, natural and anthropogenic sediment mixin...

Editors K.E. MacCormack ,R.C.Berg, H.Kessler, H.A.J. Russell and L.H. Thorleifson AER/AGS Special Report 112 2019 Synopsis of Current Three-Dimensional Geological Mapping and Modelling in Geological Survey Organizations https://ags.aer.ca/document/SPE/SPE_112.pdf

Submarine groundwater discharge (SGD) has been implicated as a significant source of nutrients and potentially harmful substances to the coastal sea. Although the number of reported SGD sites has increased recently, their stratigraphical architecture and aquifer geometry are rarely investigated in detail. This study analyses a multifaceted dataset...

Submarine groundwater discharge (SGD) has been implicated as a significant source of nutrients and other potentially harmful substances to coastal sea. Although the number of reported SGD sites has increased recently, their stratigraphical architecture and aquifer geometry are rarely investigated in detail. This study analyses a multifaceted datase...

Submarine groundwater discharge (SGD) has been implicated as a significant source of nutrients and other potentially harmful substances to coastal sea. Although the number of reported SGD sites has increased recently, their stratigraphical architecture and aquifer geometry are rarely investigated in detail. This study analyses a multifaceted datase...

The anthropogenically forced expansion of coastal hypoxia is a major environmental problem affecting coastal ecosystems and biogeochemical cycles throughout the world. The Baltic Sea is a semi-enclosed shelf sea whose central deep basins have been highly prone to deoxygenation during its Holocene history, as shown previously by numerous paleoenviro...

Soft-sediment deformation structures are preserved in clastic-biogenic varves of the Lake Nurmijärvi sequence from central-southern Finland. Deformation structures include centimeter-scale folding and faulting structures and larger convolute bedding, which are separated from the overlying undisturbed varved section by a turbidite dated at 7400 cal...

Fine-grained sediments in southern Finland were deposited during the retreat of the continental Fennoscandian ice-sheet at around 13,000 cal BP, leaving subsequent ice-contact deposits and postglacial lake and, finally, the modern brackish water Baltic Sea basin (BSB). As a result of the strong glacioisostatic land uplift of the region, these sedim...

Beryllium (Be) sources, transport and sinks were studied in a coastal landscape where acidic soils (acid sulfate soils) have developed after drainage of fine-grained sulfide-bearing sediments. The study included the determination of total abundance and speciation of Be in a variety of solid and aqueous materials in both the terrestrial and estuarin...

The European Marine Strategy Framework Directive requires the development of suitable indicators for regular reporting on the environmental state and achievement of a good environmental status of EU's marine waters by 2020. The development of indicators for determining seafloor integrity and its possible disturbance by human activities have so far...

Iron (Fe) plays a key role in sedimentary diagenetic processes in coastal systems, participating in various redox reactions and influencing the burial of organic carbon. Large amounts of Fe enter the marine environment from boreal river catchments associated with dissolved organic matter (DOM) and as colloidal Fe oxyhydroxides, principally ferrihyd...

The anthropogenically forced expansion of coastal hypoxia is a major environmental problem affecting coastal ecosystems and biogeochemical cycles throughout the world. The Baltic Sea is a semi-enclosed shelf sea whose central deep basins have been highly prone to deoxygenation during its Holocene history, as shown previously by numerous paleoenviro...

We present in situ measurement results on the vertical and temporal variability of H2S and O2 concentrations, temperature and pH in week, hour and minute scales in the western Gulf of Finland in 2013–2014. The main focus is on the 60–100 m water depth range that contained 0.4–40 μM O2 and 6.3–22.6 μM H2S. At stations where free gas was detected in...

This study explores the Holocene depositional succession at the IODP Expedition 347 sites M0061 and M0062 in the vicinity of the Ångermanälven River estuary in the Bothnian Sea sector of the Baltic Sea in northern Scandinavia. Site M0061 is located in a coastal offshore setting (87.9 m water depth), whereas site M0062 is fully estuarine (69.3 m wat...

Iron (Fe) plays a key role in sedimentary diagenetic processes in coastal systems, participating in various redox reactions and influencing the burial of organic carbon. Large amounts of Fe enter the marine environment from boreal river catchments associated with dissolved organic matter (DOM). However, the fate of this Fe pool in estuarine sedimen...

The uppermost 50 cm of sediments from the 23 m deep lacustrine basin of Nurmijärvi, a lake in south-central Finland, are composed of the clastic-biogenic type of varves. We use multiple dating methods to render a sediment chronology that is as precise and accurate as possible for future paleoenvironmental research on this high-fidelity sedimentary...

Many modern epicontinental seas were dry land before their marine flooding by the mid-Holocene glacioeustatic sea-level rise, whereas the Baltic Sea Basin was covered by a huge postglacial lake. This change from a postglacial lake to the present-day semi-enclosed brackish-water sea is studied here in sediment cores and acoustic profiles from the Ba...

This study examines the spatial and temporal distribution patterns of arsenic (As) in solid and aqueous materials along the mixing zone of an estuary, located in the south-eastern part of the Bothnian Bay and fed by a creek running through an acid sulfate (AS) soil landscape. The concentrations of As in solution form (< 1 kDa) increase steadily fro...

Human-induced spreading of coastal hypoxia is currently a growing global problem that has deleterious effects on marine ecosystems. Although long-term spatio-temporal trends in hypoxia in the offshore areas of the Baltic Sea have been widely studied, coastal areas have received less research interest so far. In addition, the conventional environmen...

The Paleoproterozoic, 2.0–1.9 Ga Talvivaara formation of Finland was deposited during the Shunga Event, a worldwide episode of enhanced accumulation of organic-rich sediments in the aftermath of the Lomagundi–Jatuli carbon isotope excursion. Sulfidic carbonaceous mudstones in the Talvivaara formation contain one of the largest known shale-hosted ni...

Based on results of geochemical and radionuclide measurements, indicators for possible causes of sediment dynamics and mixing in the Mecklenburg Bight and the Arkona Basin are investigated. Instead of expected sharp 137Cs peaks and characteristic Hg profiles the data often show blurred signals that sometimes even match each other indicating varying...

Eutrophication-induced hypoxia has resulted in preservation of laminated sedimentary fabric in coastal areas of the northern Baltic Sea. These laminites offer a potential technique for dating recently deposited organic-rich muds, but their formation mechanisms have been inadequately understood. In this study, microfabric of the modern laminated sed...

The Late Pleistocene and Holocene glacial and postglacial sediments of the Baltic Sea basin are conventionally classified into units according to the so-called Baltic Sea stages: Baltic Ice Lake, Yoldia Sea, Ancylus Lake and Litorina Sea. The Baltic Sea stages have been identified in offshore sediment cores by fundamentally different criteria, prec...

Integrated sediment multiproxy studies and modeling were used to reconstruct past changes in the Baltic Sea ecosystem. Results of natural changes over the past 6000 years in the Baltic Sea ecosystem suggest that forecasted climate warming might enhance environmental problems of the Baltic Sea. Integrated modeling and sediment proxy studies reveal i...

We present 54Fe and 56Fe data on pyrite from burrow-like and irregularly shaped pyrite concretions from Holocene postglacial lacustrine clays in the northern Baltic Sea collected using a secondary ion mass spectrometry (SIMS) microanalysis technique. The burrow-like concretions were formed in reducing, mucus-coated worm burrows in oxic surface sedi...

Dating of sediment cores from the Baltic Sea has proven to be difficult due to uncertainties surrounding the 14C reservoir age and a scarcity of macrofossils suitable for dating. Here we present the results of multiple dating methods carried out on cores in the Gotland Deep area of the Baltic Sea. Particular emphasis is placed on the Littorina stag...

Abstracts submitted to the 11th Colloquium on Baltic Sea Marine Geology, Helsinki 19th−21st September 2012

Dating of sediment cores from the Baltic Sea has proven to be difficult due to uncertainties surrounding the 14C reservoir age and a scarcity of macrofossils suitable for dating. Here we present the results of multiple dating methods carried out on cores in the Gotland Deep area of the Baltic Sea. Particular emphasis is placed on the Littorina stag...

Late Holocene sediments in the Baltic Sea provide an opportunity to study lateral changes in the assemblages of identifiable biogenic sedimentary structures (ichnofossils) in a large, high-latitude semi-enclosed sea with instrumentally determined gradients in biodiversity and environmental factors such as salinity and ox-ygen availability. Integrat...

In this study, particulate organic carbon (POC) contents and their distribution pattern in surficial sediments of the Baltic Sea are presented for 1,471 sampling stations. POC contents range from approx. 0.1% in shallow sandy areas up to 16% in deep muddy basins (e.g. Gotland Basin). Some novel relationships were identified between sediment mass ph...

This study investigates the geochemistry of soft, organic-rich brackish-water surface sediments in the Archipelago Sea (SW Finland). The area is one of the world's largest archipelagos, and, although it is scarcely populated, frequent ship and boat traffic along with fish farming occurs. From 76 sites, 47 chemical elements were determined after aqu...

Two ca 8000 year long sediment cores from the Gotland Deep, the central sub-basin of the Baltic Sea, were studied by means of digital images, X-radiographs and scanning electron microscopy–energy-dispersive X-ray mineralogical analysis to gain understanding of the physicochemical and biological influences on sedimentary-fabric formation in modern a...