15. Marine geology
15.1. Tectonic, geodynamic, oceanographic, and cryospheric evolution of the Arctic Ocean from Mesozoic to present day
The Opening of the Arctic-Atlantic Gateway: Tectonic, Oceanographic and Climatic Dynamics – Status of the IODP Initiative
Wolfram Geissler1 and Jochen Knies2
1Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, 27568 Bremerhaven, Germany, 2Geological Survey of Norway, 7491 Trondheim, Norway/CAGE, University of Tromsø, 9037 Tromsø, Norway
The modern polar cryosphere reflects an extreme climate state with profound temperature gradients towards high-latitudes. It developed in association with step-wise Cenozoic cooling, beginning with ephemeral glaciations and the appearance of sea ice in the late middle Eocene. The polar ocean gateways played a pivotal role in changing the polar and global climate, along with declining greenhouse gas levels. The Arctic Ocean was an isolated basin until the early Miocene when rifting and subsequent sea-floor spreading started between Greenland and Svalbard, initiating the opening of the Fram Strait / Arctic-Atlantic Gateway (AAG). Although this gateway is known to be important in Earth’s past and modern climate, little is known about its Cenozoic development. The opening history and AAG’s consecutive widening and deepening must have had a strong impact on circulation and water mass exchange between the Arctic and the North Atlantic Oceans. To study the AAG’s complete history, ocean drilling sites in the Boreas Basin and along the East Greenland continental margin are proposed. These sites will provide unprecedented sedimentary records that will unveil the history of shallow-water exchange between the Arctic and the North Atlantic Oceans, and the development of the AAG to a deep-water connection and its influence on the global climate system.
Getting a continuous record of the Cenozoic sedimentary succession that recorded the evolution of the Arctic-North Atlantic horizontal and vertical motions, and land and water connections will also help better understanding the post-breakup evolution of the NE Atlantic conjugate margins and associated sedimentary basins.
Depositional history of the western Amundsen Basin, Arctic Ocean
John R. Hopper1, Carlos Castro2, Paul Knutz1 and Thomas Funck1
1Geological Survey of Denmark and Greenland, 2Niels Bohr Institute
Seismic reflection data collected in the western Amundsen Basin show a uniform and continuous cover of sediments over oceanic basement. An interpretation of seismic facies units shows that the depositional history of the basin reflects changing tectonic, climatic, and oceanographic conditions throughout the Cenozoic. The early history of the basin shows a tectonically influenced restricted basin that gave way in the early to mid-Miocene to a bottom current dominated environment indicated by a buildup of contourite deposits. It is suggested that this is a response to the opening of the Fram Strait and the establishment of geostrophic bottom currents that flowed from the Laptev Sea towards Greenland. These deposits are overlain by a seismic facies unit characterized by buried channels and erosional features. These include prominent basinward levee systems that suggest a channel morphology maintained by overbank deposition of muddy sediments carried by suspension currents periodically spilling over the channel pathway. These deposits indicate a change to a much higher energy environment that is proposed to be a response to brine formation associated with the onset of perennial sea ice cover in the Arctic Ocean. This interpretation implies that the development of significant sea cover results in a significant change in the energy environment of the ocean that is reflected in the depositional and erosional patterns observed. The lack of similar high energy erosional features and the presence of contourite deposits throughout most of the Miocene may indicate the Arctic Ocean was relatively ice-free until the very latest Miocene.
Arctic Climate Perturbations during the Early Triassic Biotic Crisis
1Geological Survey of Norway
Fractured and kaolinite weathered basement rocks have been discovered in various wells off the Norwegian coast and inferences on timing, source to sink relationships, and environmental implications have been widely discussed. The reason for the kaolitinization has often been related to intensive chemical weathering during late Triassic to early Jurassic times. Chronological control has primarily been inferred from the overlying late Jurassic/early Cretaceous marine transgression and poorly constrained K-Ar datings from weathered basement onshore as well as climate conditions favourable for kaolinite formation.
In this study, I present evidence that the deeply weathered basement off the mid-Norwegian coast represent a complete paleosol profile formed ca 250 million years ago. The timing corroborates with the Early Triassic biotic crisis and suggest a causal relationship between intense chemical weathering, high atmospheric CO2 concentration, extreme ocean warming, delayed biotic recovery, increased riverine flux of nutrients and widespread anoxia/euxinia in the high northern latitudes during a time of rapid global climate perturbations.
Greenland Ice Sheet evolution and dynamics seen from the perspective of a large glacial fan system, northeast Baffin Bay
Paul C Knutz1, Andrew M W Newton2, John R Hopper1, Mads Huuse3, Ulrik Gregersen1, Emma Sheldon1 and Karen Dybkær1
1Geological Survey of Denmark and Greenland, Øster Vold Gade 10, 1350 Copenhagen, Denmark, 2School of Earth and Environmental Sciences, University of Manchester, M13 9PL, UK, 3Cryosphere Research at Manchester (CRAM), University of Manchester, M13 9PL, UK
The Greenland Ice Sheet (GrIS) is a major freshwater reservoir and a key component of the global climate system so understanding its past dynamic behaviour is crucial for underpinning climate model predictions. The long-term history of the GrIS is mainly deduced from deep ocean drilling sites while relatively little information exists from its dynamic glacial margins. Here we present mapping results, based on a dense 2D reflection-seismic grid tied to industry well data, which illuminates the stratigraphy and spatial evolution of the Melville Bugt – Upernavik trough-mouth fan system. The fan depocentres, formed by sediments eroded and transported by the northern GrIS, are constructed by sequentially organized prograding depositional units, bounded by glacial erosion surfaces that extend into steeply dipping clinoforms on the outer margin. South of the main trough, the erosion surfaces are commonly onlapped by laterally continuous strata attributed to sea-level transgressions. The study reveals eleven phases of ice stream advance over the northwest Greenland continental margin since the onset of shelf-based glaciation at around 2.8 Ma. The GrIS advance phases were interrupted by glacial retreats and sea-level rises that appear to correlate with super-interglacial periods identified in the Siberian Arctic region. Moreover, a change in ice flow configuration from uniform glacial advances to distinct trough-based drainage points to a major change in GrIS dynamics through the Mid-Pleistocene transition.
On the origin of the marginal plateaus north of Svalbard and Greenland
Yngve Kristoffersen1, Yoshihide Ohta2, John K. Hall3 and Geir B. Larsen4
1University of Bergen/Nansen Environmental and Remote Sensing Centre, 2(retired) Norwegian Polar Insititute, 3(retired) Geol. Survey of Israel, 4Lundin-Norway
The marginal plateaus north of Svalbard and Greenland are conjugate features with respect to the Gakkel Ridge and likely to share a geologic history.
Dredge hauls from three sites on the Yermak Plateau have recovered an abundance of metasediments and gneisses with strong affinities to known lithologies from northwest Spitsbergen. The results support the earlier idea of the plateau being a continental outlier except for its northeasternmost tip. The outlier rifted off the margin north of Svalbard and moved with the Greenland plate which implies significant Paleogene dextral shear motion close to the coast of Spitsbergen. Past coast-parallel shear is supported by observed seismic velocity anomalies in the crust characteristic of continental transform boundaries.
A seismic reflection transect across Morris Jesup Rise show an eastern flat-topped spur of undeformed west-dipping layers and a western dome-structure cored by deformed sediments, possibly an imbricate stack of thrust sheets. High amplitude rough seismic reflections interpreted as lava flows are present at depth in the 40 km wide depression between these two structures.
The shared geologic history of the marginal plateaus involve Yermak Plateau rifting off north of Svalbard at Chron 24 and the eastern Morris Jesup Spur rifting off the Yermak Plateau at about Chron 15. The Morris Jesup Spur is likely to represent the pre-Cenozoic continental slope north of Svalbard.
Late Cenozoic paleoenvironment and erosion estimates for the northeastern Svalbard/northern Barents Sea continental margin, Norwegian Arctic
Amando Lasabuda1, Wolfram Geissler2, Jan Sverre Laberg3, Stig-Morten Knutsen4, Tom Arne Rydningen3 and Kai Berglar5
1Research Centre for Arctic Petroleum Exploration (ARCEx), IG, University of Tromsø, Norway, 2Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung (AWI), Bremerhaven, Germany, 3Department of Geosciences, University of Tromsø – the Arctic University of Norway, Tromsø, Norway, 4Norwegian Petroleum Directorate (NPD), Harstad, Norway, 5Federal Institute for Geosciences and Natural Resources (BGR), Hannover, Germany
The upper Cenozoic sedimentary succession of the northeastern Svalbard/northern Barents Sea continental margin is analyzed using available 2D seismic data. The primary focus is to better understand the glacial paleoenvironments and sedimentary processes as well as to estimate the glacial erosion of the inferred source areas. Seismic facies analysis shows three main facies; parallel to oblique parallel, contorted, and chaotic seismic patterns. These observations suggest an interplay between contour current and glacial-related mass-wasting processes. The seismic mapping shows abundant contourite deposition since the Miocene, interpreted to be related to the establishment of an ocean circulation system following the opening of the Fram Strait, similar to present conditions. The glacigenic debrites and its associated mass-transport deposits are interpreted to characterize the area in front of the troughs. This is likely related to extensive glaciations in the Plio-Pleistocene during which ice sheets repeatedly advanced to the shelf break during the full-glacial conditions. The inter trough-mouth fan areas appear to be dominated by contouritic deposits characterized by a series of sediment waves and sheeted drifts. In the studied margin, there is an increasing trend of mass-wasting processes eastwards, while along-slope processes dominate to the west. Isopach maps of the glacial strata will be presented along with the erosion estimates using a mass-balance approach. Major sediment source areas will be discussed in relation to the late Cenozoic history of this studied margin. This contribution will be useful to better understand the dynamics of uplift and erosion events in the greater Barents Sea area.
Enigmatic craters and giant gas flares in the central Barents Sea
Francis Chantel Nixon1, Shyam Chand1 and Terje Thorsnes1
1Norges geologiske undersøkelse
Recent analyses of high-resolution multibeam swath bathymetry and water column data collected from the central Barents Sea resulted in over 300 new observations of active gas flares emanating from southeast Storbanken (~100-200 m below modern sea level; mbsl). Seabed fluid escape features, including pockmarks, craters, and mounds (tentatively interpreted as gas hydrate pingos; GHPs) were also mapped in this area. Interestingly, mapped fluid escape features do not coincide with the locations of the active gas flares, which is in contrast to hundreds of similar craters, GHPs, and co-located gas flares ~300 km southwest, at depths of 310-370 mbsl (Andreassen et al., 2017). The GHPs and craters observed on southeast Storbanken occur outside of the methane hydrate stability limit, indicating that the gas hydrates underlying the GHPs constitute a mix of methane and heavier natural gases, which remain stable at shallower water depths and/or warmer temperatures. The craters, most of which are immediately adjacent to the GHPs, indicate that methane hydrates (≥99.9% methane) were formerly present, but became unstable and dissociated from the seabed, likely between ~12 – 15 ka BP following deglaciation. Depending on future warming of bottom waters in the Barents Sea, the gas hydrates underlying the GHPs on southeastern Storbanken could dissociate rapidly, forming new craters and sending large quantities of methane to the sea surface and atmosphere. Such events have important implications for both seabed geohazard mapping and for climate change models, which must take into account all sources and sinks of methane, a powerful greenhouse gas.
Andreassen, K., Hubbard, A., Winsborrow, M., Patton, H., Vadakkepuliyambatta, S., Plaza-Faverola, A., Gudlaugsson, E., Serov, P., Deryabin, A., Mattingsdal, R., Mienert, J., Bünz, S. 2017. Massive blow-out craters formed by hydrate-controlled methane expulsion from the Arctic seafloor. Science 356, 948-953.
An automated cryogenic magnetometer at the Geological Survey of Norway for natural remanent magnetization and rock magnetism: A case study of North-East Atlantic continental margin sediments
Martin Klug1, Karl Fabian2, Jochen Knies2 and Simone Sauer3
1Geological Survey of Norway, Trondheim, Norway, 2Geological Survey of Norway, Trondheim, Norway; CAGE – UiT The Arctic University of Norway, Tromsø, 3CAGE – Centre for Arctic Gas Hydrate, Environment and Climate; UiT The Arctic University of Norway
A new, automatically operating cryogenic magnetometer system at the Geological Survey of Norway is used to acquire natural remanent magnetization (NRM) and rock magnetic parameters from two locations, West Barents Sea (~71.6°N,16.2°E) and Vestnesa Ridge, NW Svalbard (~79.0°N, 6.9°E). The magnetometer lab setup comprises an automated robot sample feeding, dynamic measurement operation and monitoring, and customised output-to-database data handling. The setup is designed to dynamically enable a variety of parallel measurements with several coupled devices (e.g. balance, MS2B) to effectively use dead-time in between the otherwise time-consuming measurements with the cryogen magnetometer. Web-based access allows remote quality control and interaction 24/7 and enables high sample throughput.
In the studied cores the magnetic properties are combined with geophysical, geochemical measurements and optical imaging, both radiographic and colour images, from high-resolution core-logging. The multidisciplinary approach enables determination and interpretation of content and formation of the magnetic fraction, and its development during diagenetic processes. Besides palaeomagnetic age determination the results offer the opportunity to study sediment transformation processes that have implications for the burial and degradation of organic matter. The results also help to understand long and short-term variability of sediment accumulation. Chemical sediment stability is directly linked to environmental and climate variability in the polar marine environment during the recent past.
The general seafloor morphology of the NE Greenland shelf – Insights from new marine shallow seismic and core data collected during the NorthGreen2017 expedition
Lasse Nygaard Eriksen1, Katrine Juul Andresen1, Tove Nielsen2, Christof Pearce1, Tine Lander Rasmussen3, Hans Røy4 and Marit-Solveig Seidenkrantz1
1Department of Geoscience – SeisLab and Centre for Past Climate Studies, Aarhus University, 2Department of geophysics, Geological Survey of Denmark and Greenland, 3Department of Geosciences, UiT, The Arctic University of Norway, 4Department of Bioscience – Center for Geomicrobiology, Aarhus University
We present preliminary observations from seismic data supported by marine sediment cores from the NE Greenland shelf between 80°N and 74°N. The data were acquired in nearly ice-free conditions and consist of ~2200 km of shallow seismic subbottom profiler data as well as sediment cores from 15 different sites. The data were acquired during the NorthGreen2017 expedition in September 2017, and represent an area that has been rarely accessed due to mostly perennial sea-ice cover prior to 2017.
The data cover a wide range of different geological provinces across the NE Greenland shelf, but can roughly be subdivided into deep troughs (formed by glacial erosion) and basement highs, which also appear to be affected by glaciers. In nearly all areas, a thin cover (1-3 m) of most likely Holocene mud drapes the varying structures. Sedimentary basins (with estimated mud/clay thickness up to ca. 15-20 m) were only encountered in a few places on the shelf, primarily linked to glacier outlet troughs.
Varying seafloor morphologies can be recognized such as blocky and faulted seafloor, rugged seafloor possibly related to slope failures, potential iceberg plough-marks, basement outcrops and flat seafloor related to minor sedimentary basins. Similarly, the reflections below the seafloor show varying characteristics such as parallel high-amplitude continuous reflections and low-amplitude discontinuous chaotic reflections indicative of changing subsurface.
Active fault systems and submarine landslides along the Eastern Sakhalin slope, the Okhotsk Sea
D.D. Rukavishnikova1, K. A. Dozorova1 and B.V. Baranov1
1Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia
Continuous sub-bottom profiling and detailed bathymetry maps obtained during international projects in 1998-2015 has first revealed areas of active tectonics and associated submarine landslides within central and northern areas of Sakhalin Island slope, the Okhotsk Sea. Active faults form two local systems within limited areas. Within the northern area the fault system contains NE and NW striking normal and strike-slip faults. In this area tectonic deformation caused displacement and destruction of a sediment block with approximate volume of 16 km3. NW striking normal faults form steep instable tectonic scarps up to 120 m high. Seismic survey reveals mass transport deposits with estimated total volume of 3 km3 at the base of the largest scarp Within the central slope segment the active fault system contains NE and NS striking normal and strike-slip faults. Vertical displacements along the NE normal faults result in subsidence of sediments and form closed depressions with steep walls. Failure of one of such steep walls formed a landslide with volume of about 4 km3. The presented data show that the active tectonics creates favorable conditions for landslides generation in the study area.
15.2. Paleo‐landscape analysis based on high‐resolution marine data
The impact of a buried shear margin moraine and thermokarst landscapes on ice-stream dynamics of the SW Barents Sea revealed by high-resolution 3D seismic data
Benjamin Bellwald1, Sverre Planke1, Nina Lebedova-Ivanova1, Emilia Daria Piasecka2, Mohamed Ali Matar3, Karin Andreassen2 and Reidun Myklebust4
1Volcanic Basin Petroleum Research (VBPR), 2UiT The Arctic University of Norway, 3Nordic Geo-Consult, 4TGS
Meter-scale glacial landforms and layers, not resolvable by conventional seismic data, comprise new information about glacier dynamics and fluid flow, which are valuable for the development of offshore infrastructure and geohazard assessments. The goal of this study is to characterize the paleo-landscape of the SW Barents Sea on a meter-scale, to correlate these structures with the sub-surface geology and to study their implications on ice-stream dynamics. The database consists of c. 200 km2 of high-resolution P-Cable 3D seismic data and 37 gravity cores in the SW Barents Sea. The grids of the picked seabed and Upper Regional Unconformity (URU) horizons, which define the top and base of the Quaternary sediment sequence, are compared with interpretations obtained from conventional 3D seismic and multibeam echosounder data. Seabed images interpreted in P-Cable 3D seismic data show an increased resolution and sharpness compared to surfaces derived from multibeam echosounder and conventinal 3D seismic data. Hill-hole pairs and rhombohedral ridges at URU are interpreted as geological structures formed by subglacial thermokarstic processes, indicating the presence of permafrost. Reflections within the intraglacial sediment package are not visible in conventional seismic data, and include a shear margin moraine, mass tranport deposits and soft beds. This study shows that high-resolution seismic data can be used to identify geological structures in multibeam echosounder quality of both the seabed and the shallow sub-surface. Identified thermokarst landscapes, a submarine braided river and a shear margin moraine have led to the development of a revised ice-stream model of the SW Barents Sea.
Geological setting of Anholt Loch (Site M0060) IODP Expedition 347
Jørn B. Jensen1, Ole Bennike2, Katrine J. Andresen3 and Ole Rønø3
1Department of Marine Geology, Geological Survey of Denmark and Greenland (GEUS), 2Department of Marine Geology, Geological Survey of Denmark and Greenland (GEUS)., 3Deparment of Geoscience, Aarhus University
IODP Expedition 347 Site M0060 is situated in the southern Kattegat at a water depth of 34m. The background selection of the coring position was a rather coarse grid of seismic lines, that indicates an erosional valley southeast of Anholt Island in the Kattegat Sea. The valley was originally interpreted as infilled by a sequence from MIS 6, MIS 5e, and MIS 3 (Lykke-Andersen et al. 1993). Later boomer profiles and shallow cores show, that the younger parts of the infill is late glacial and Holocene age (MIS 2–MIS 1; Jensen et al. 2002).
In 2013 the IODP program core M0060 reached a total depth of 232.5m of which 0 to 9 mbsf is Marine Holocene and the range 9 to 82 mbsf covers the most recent deglaciation 14 – 18 ka BP i.e. (Bokhari 2015). On greater depths alternating sandy and silty sequences are recorded, while the lowermost 84 m consists of diamict.
Parallel to Expedition 347 a local Danish – Swedish project DAN-IODP-SEIS carried out High Resolution 2D seismics (Nørmark et al. 2014) and in spring 2017 a 3D high resolution survey was carried out in connection with the Geocenter Denmark project SEDI-TRAPS.
Correlation of the coring results and the seismic data show that the Anholt Lock is linked closely to the structural development of the Tornquist Zone strike-slip fault system and synsedimentary Late- and Postglacial depositional patterns document that reactivation has taken place.
Bokhari Friberg, Y., 2015: The paleoceanography of Kattegat during the last deglaciation from benthic foraminifer-al stable isotopes. Dissertations in Geology at Lund University, No. 461, 30 pp. 45
Jensen, J.B., Petersen, K.S., Konradi, P., Kuijpers, A., Bennike, O., Lemke, W., & Endler, R., 2002: Neotectonics, sea level changes, and biological evolution in the Fennoscandian border zone of the southern Kattegat Sea. Boreas, 31(2):133–150.
Lykke-Andersen, H., Seidenkrantz, M.-S., & Knudsen, K.L., 1993: Quaternary sequences and their relations to the pre-Quaternary in the vicinity of Anholt, Kattegat, Scandinavia. Boreas, 22(4):291–298
Nørmark, E., Bendixen, C., Jensen, J.B., Clausen, O.R., 2014: Simultaneous acquisition of airgun seismic and high resolution sparker data – combining the two types of data. Near Surface Geoscience 2014, pp 1–5
Postglacial paleo-landscape evolution of Aalborg Bay-Læsø Rende, northwestern Kattegat – results of a regional aggregate raw material mapping campaign
Niels Nørgaard-Pedersen1, Jørgen O. Leth1, Ole Bennike1 and Steen Lomholt1
1Geological Survey of Denmark and Greenland
In 2016 a regional shallow seismic mapping campaign for aggregate raw materials took place in an 1800 km2 area in Aalborg Bay in northwestern Kattegat. The main purpose of the study, performed for the Danish Environmental Agency, was to assess the distribution and quality of aggregate material as well as monitoring the habitat conditions in the area. Mapping of basis of the Holocene deposits in the area, representing the low stand period at about 12.000-10.000 yrs. BP, reveals a network of valley/channel systems which appear to be connected to the major drainage systems connected to inlets of eastern Jutland. Rapidly increasing relative sea level from about 10.000-7.000 yrs. BP enhanced marine transport of very large volumes of sandy material from the northwestern Kattegat in to the northern part of the study area. Elongated sand bars tens of kilometers long formed in Læsø Rende. In the mid-Holocene at about 5000-4000 yrs. BP relative sea level culminated at about 4-5 m above present sea level. Due to the continued isostatic uplift of the northern part of Kattegat relative sea level fell after c. 4000 yrs BP. The large sand bar and intervening channel systems were selectively eroded and large amounts of sandy material were transported southward to the central deeper part of Aalborg Bay. The development of a geological model encompassing the present distribution of specific stratigraphic units and the related paleo-landscape evolution in relation to sea level changes, is an important prerequisite for predicting aggregate raw material distribution and quality variability.
Glaciotectonic thrust complex offshore Holmsland, the Danish North Sea – New Results.
Bernhard Novak1 and Henrique Duarte2
1Independent, 2Geosurveys Ed
Geological structures and seismic stratigraphy of a large-scale glaciotectonic thrust complex has been investigated in an area 5 km offshore along the coastline off the Holmsland Dunes area, west Denmark. A dense grid of seismic data combined with surface samples and boreholes information have been analyzed in a 6 by 15 km area. The base of the Quaternary (D,b) constitutes an unconformity interface to Neogene. A smooth seismic horizon (D,d) that outline ramps and flats constitutes a decollement surface beneath the thrust complex. New analysis (and data) yield evidences that the base Quaternary unconformity is unaffected by the deformation and that near horizontal parallel seismic facies onlaps D,b. The seismic unit D,0 between the horizons D,b and D,d shows medium to high amplitude parallel (onlap), mound, channel, oblique and chaotic seismic facies. This 0 to 30 meter thick seismic unit is interpreted to represent glaciolacustrine laminated sediments (parallel facies) deposited over a proglacial outwash plain environment. Analysis of thrust block dip variations above D,0 suggests a correlation to the thickness of unit D,0 and the thrust style. In areas where the unit is absent a fold/dome deformation style at the base of the complex is accompanied by steep thrust style and maximum space between thrust ridges above the folds. Our model suggests that unit D,0 function as a hydro conductive agent beneath tens of meters of glaciolacustrine deposit. Variations in the appearance of unit D,0 and lithological variations in the lacustrine deposits results in variations in thrust style.
Lee, J.R., Phillips, E., Booth, S.J., Rose, J., Jordan, H.M., Pawley, S.M., Warren and Lawley, R.S. 2013: A polyphase glacitectonic model for ice-marginal retreat and terminal moraine development: the Middle Pleistocene British Ice Sheet, northern Norfolk, UK. Proceedings of the Geologists Association, 124, p.753–777
Nieuwland, D.A., Leutscher, J.H. and Gast, J. 2000: Wedge equilibrium in fold-and-thrust belts: prediction of out-of-sequence thrusting based on sandbox experiments and natural examples. Geologie en Mijnbouw / Netherlands Journal of Geosciences, 79, (1)p. 81-91
Novak, B., Duarte, H. and Leth, J.O. 2015: Glaciotectonic thrust complex offshore Holmsland, the Danish North Sea. Abstract in The Quaternary Geology of the North Sea, Annual discussion Meeting of the Quaternary Research association UK, Edinburgh, January,2015
Piotrowski, J., and Tulaczyk, S., 1999: Subglacial conditions under the last ice sheet in NW Germany: Ice-bed separation and enhanced basal sliding?: Quaternary Science Reviews, 18, p. 737-751
Paleo-river valleys near the Dogger Bank in the Danish and German sectors of the North Sea – an undiscovered tributary system to the Paleo Elbe Valley
Trine Andreasen1, Katrine Juul Andresen1, Daniel A. Hepp2 and Hanno Keil3
1SeisLab Aarhus, Department of Geoscience, Aarhus University, Høegh-Guldbergs Gade 2, 8000 Aarhus C, 2Centre for Marine Environmental Sciences, MARUM, Bremen, 3Faculty of Geosciences, University of Bremen
This study presents a new system of paleo-river valleys southeast of the Dogger Bank which has been mapped using high-resolution subbottom profiler data and sediment cores acquired during a RV Heincke expedition to the German and Danish sectors of the North Sea in May 2016.
The paleo-river system covers an area of approx. 200 km2 and is found below a thin succession of marine sediments, which indicates that the river system formed prior to the marine transgression 8000 years ago. The river system is characterised by a central, 5 km wide and up to 6 m deep NE-SW striking valley that intersects six older and smaller NW-SE striking channels.
The course of the wider central valley roughly follows the contours of the submerged Dogger Bank and the infill of the valley is characterised by well-defined subparallel and continuous reflections. This suggest a steady infilling of the valley, which may have occurred within an estuary environment prior to the marine transgression.
The six older and smaller channels have higher sinuosity and follows a course perpendicular to the Dogger Bank. These channels are interpreted to constitute an older meandering river system dewatering the Doggerland and terminating in the Paleo-Elbe Valley east of the study area.
The six older meandering rivers can be readily linked to other similar systems mapped further southeast (Hepp et al., 2017) and there is generally a very good agreement of our new findings with the existing theories on the development of the Doggerland landscape since the Weichselian lowstand.
Hepp DA, Warnke U, Hebbeln D, Mörz T. 2017. Tributaries of the Elbe-Palaeovalley: features of a hidden palaeolandscape in the German Bight, North Sea. In Under the Sea: archaeology and palaeolandscapes of the continental shelf, Bailey GN, Harff J, Sakellariou D (eds.). Coastal Research Library vol. 20, Springer; 211-222.
Late glacial to Holocene geological development of the western Limfjord – reconstruction of a dynamic paleolandscape
Katrine Juul Andresen1, Anders Dahlin2, Kasper U. Kjeldsen3, Hans Røy3 and Marit-Solveig Seidenkrantz4
1SeisLab Aarhus, Department of Geoscience, Aarhus University, Høegh-Guldbergs Gade 2, 8000 Aarhus C, 2SeisLab Aarhus, Department of Geoscience, Aarhus University, 3Centre for Geomicrobiology, Department of Bioscience, Aarhus University, 4Centre for Past Climate Studies, Department of Geoscience, Aarhus University
The western Limfjord in northern Denmark comprises wider water-areas such as Løgstør and Thisted Brednings, narrow straits, small islands and some larger islands with spectacular landscapes such as Mors and Fur. The Quaternary development of the fjord has been highly governed by surface processes related to changing ice-covers which has carved-out the fjord, deformed the Cenozoic succession including the Eocene Mo-clay by thrusting and folding, and generated sea-level fluctuations due to ice-melting and isostatic glacial rebound. At the same time, deep geological subsurface processes such as rising salt diapirs, tectonic faulting and fluid migration have also controlled the formation of the landscape.
In this study, we present a detailed subsurface investigation of Visby Bredning in the western Limfjord based on high-resolution seismic data and sediment cores acquired during the WesternLimfjord-expedition in May 2017. Our preliminary results show that the Quaternary paleolandscape from the seismic data as expected is very dynamic, and most likely have recorded the history from an ice-covered to shallow-water environment. The seismic data typically show a distinct transition from high-amplitude chaotic reflections interpreted as Weichselian till, to lower amplitude, semi-parallel, continuous reflections interpreted as the Holocene succession. A few places, we observe a third unit in between the glacial and Holocene units, which we tentatively suggest could represent late glacial deposits. Sediment descriptions and age dating from two gravity cores in Visby Bredning are included to address the Holocene development in more detail and unravel the changing influence of fresh, brackish and marine waters in Visby Bredning.
The Young Sound fjord system, NE Greenland – Insights from new marine shallow seismic and core data collected during the NorthGreen2017 expedition
Lasse Nygaard Eriksen1, Katrine Juul Andresen1, Tove Nielsen2, Christof Pearce1, Tine Lander Rasmussen3, Sofia Ribeiro2, Søren Rysgaard4, Hans Røy5 and Marit-Solveig Seidenkrantz1
1Department of Geoscience – SeisLab and Centre for Past Climate Studies, Aarhus University, 2Department of geophysics, Geological Survey of Denmark and Greenland, 3Department of Geosciences, UiT, The Arctic University of Norway, 4Department of Bioscience – Arctic Research Centre, Aarhus University, 5Department of Bioscience – Center for Geomicrobiology, Aarhus University
The Young Sound fjord system in NE Greenland generally consists of an outer, up to 7 km wide, shallow water (<200 m) part and an inner narrow (2 km wide) and deeper water (300-400 m) part known as the Young Sound Deep. The fjord system have been extensively surveyed for marine, terrestrial and meteorological data since 1994 (Bendtsen 2014 et al.), but the underlying seafloor and the subsurface sediments have to our knowledge only been mapped superficially. In this study, we present preliminary observations from seismic mapping and sediment coring within the Young Sound. The data that consist of 400 km of shallow seismic subbottom-profiler data and four sediment cores were acquired during the NorthGreen2017 expedition in September 2017 and represent the first detailed marine seismic study of the geological development of the fjord system.
We show that the central basin in Young Sound Deep is filled with a fairly thick sediment package (at least 40-50 m where thickest). There was furthermore a clear distinction in both the seafloor morphology and the subsurface geology from the inner part of the fjord towards the outer part of the fjord, which is most likely a direct representation of the similar marked changes in topography at the fjord sides. Thus, our observations from the high-resolution shallow-seismic data suggest that we can track first-order erosion and depositional processes within the fjord back in time.
Bendtsen, Jørgen, John Mortensen, and Søren Rysgaard. “Seasonal surface layer dynamics and sensitivity to runoff in a high Arctic fjord (Young Sound/Tyrolerfjord, 74 N).” Journal of Geophysical Research: Oceans 119.9 (2014): 6461-6478.
Deep geology at Vejle Fjord – Paleogene structural control of a Quaternary fjord system
Jakob Roued1, Marit-Solveig Seidenkrantz1, Lars Ole Boldreel2 and Katrine Juul Andresen1
1SeisLab Aarhus and Centre for Past Climate Studies, Department of Geoscience, Aarhus University, 2Department of Geosciences and Natural Resource Management, University of Copenhagen
Vejle Fjord in Denmark is believed to have formed as a tunnel valley initially carved-out during the Elsterian glaciation and later reused and expanded during succeeding glaciations and inter-glaciations. Folds and thrust faults in the present-day coast-profiles of the fjord bear evidence of glacial deformation while outcrops of Paleogene and Neogene sediments have aided the reconstruction of the paleolandscape. It has however not been investigated in detail, how deeper geological structures could have controlled and effected the configuration of the pre-Vejle Fjord landscape and in turn the focus of the Quaternary glacial processes.
In this study, we interpret newly acquired high-resolution 2D seismic data and sediment cores from Vejle Fjord with the aim of mapping and investigating the deeper geological structures and their potential influence on the formation of the fjord. Our seismic data show a number of faults, which in the southern part of Vejle Fjord offset Eocene sediments presently at the seafloor. The faults can be followed down to ca. 70 m below the seafloor, with a few faults continuing even deeper. Three hypotheses for the formation of the faults are suggested: Quaternary glacial tectonic deformation, slope failure deformation, and polygonal faulting. Which of the hypotheses that are applicable have a great importance for the understanding of the early origin of Vejle Fjord and for fjord formation in sedimentary basins in general. To understand the faults, our interpretation is focused on constraining their 3D geometries and in turn their timing, activity and controlling factors.
15.3. The Quaternary geology of the North Sea Basin
The Quaternary Stratigraphy in the Norwegian Sector of the Central North Sea – A Site Survey Perspective
Quaternary deposits of the North Sea are of particular interest for geohazard and site characterisation studies ensuring the save emplacement of offshore installations (IOGP 2013 & 2015). A coherent (litho-)stratigraphic framework is required in order to perform a reliable interpretation of geophysical and geotechnical site survey data and in order to ensure the comparability of results.
The British sector of the North Sea has been systematically mapped by the British Geological Survey. Reports and maps presenting seabed sediments and the Quaternary geology have been published (e.g. Johnson et al. 1993, Gatliff et al. 1994). Such systematic mapping has not been undertaken in the Norwegian sector of the southern and central North Sea. Therefore, the interpretation of site survey data in the Norwegian sector is often based on the extrapolation of the British stratigraphic model, leading to a considerable degree of uncertainty and inconsistency. Recent research has improved the understanding of Quaternary deposits (e.g. Buckley 2014, Ottesen et al. 2014). However, many studies focus on the early Quaternary sequence or make use of conventional 3D exploration seismic data that have a relatively low resolution and do not image the complexity of middle and late Quaternary deposits.
This presentation will highlight issues and challenges regarding the Quaternary stratigraphy in the central North Sea as seen from a site survey perspective. Examples of high-resolution data will be shown from site surveys in the Norwegian sector and in areas crossing the UK-Norway border.
Buckley, F.A. 2014: Re-evaluating Shallow Geology in the Central North Sea. Near Surface Geoscience 2014 – First Applied Shallow Marine Geophysics Conference, EAGE, Extended Abstracts, DOI: 10.3997/2214-4609.20142112.
Gatliff, R.W., Richards P.C., Smith, K., Graham C.C., McCormack, M., Smith, N.P., Long, D., Cameron, T.D.J., Evans, D., Stevenson, A.G., Bulat, J. & Ritchie, J D. 1994: United Kingdom offshore regional report: The geology of the central North Sea. London: British Geological Survey. 118 pp.
International Association of Oil & Gas Producers (IOGP) 2013 & 2015: Conduct of offshore drilling hazard Site Surveys – Guidelines & Technical Notes. IOGP Reports No. 373-18-1 & 373-18-2.
Johnson, H., Richards P.C., Long D. & Graham C.C. 1993: United Kingdom offshore regional report: The geology of the northern North Sea. London: British Geological Survey. 110 pp.
Ottesen, D., Dowdeswell, J.A. & Bugge, T. 2014: Morphology, sedimentary infill and depositional environments of the Early Quaternary North Sea Basin (56°–62°N), Marine and Petroleum Geology 56, 123-146, DOI: 10.1016/j.marpetgeo.2014.04.007.
The Norwegian Strandflat – an offshore perspective
1Statoil ASA, R&D Trondheim
The strandflat is the picturesque world-heritage topographic low-land, island and sounds on the coast of Norway. The age and processes of forming the strandflat have been debated since first described by Hans Reusch in 1900. The objective of this work is set constrains to the age and formation processes of the strandflat by linking it to the offshore geological evolution. Seismic and well data are used to interpret the Cenozoic geological evolution of the margin while the strandflat is studied through literature and field observations.
The non-parallel tilts of the strandflat relative to offshore Cenozoic surfaces show that the strandflat was formed during the Quaternary.
The strandflat is widest, up to 50 km, on the mid Norwegian coast. The combined effect of glacial erosion (volume-vice most important) and wave erosion formed the strandflat. Wave erosion cut leveled platforms into the glacial-segmented coast. This occurred most efficiently during glacial periods when the coast was ice-free simultaneously as the land was depressed under the weight of the inland ice. During repeated glacial and intra-glacial events the platform grew wider and deeper simultaneously as the coast gradually rose and tilted westward under isostatic adjustments form onshore erosion and offshore deposition. Outside Møre and Troms the strandflat is isostaticly forced below the sea level under the weight of the two glacial depocenters, the North Sea Fan and the Bjørnøya Fan. The absence of the strandflats in Finnmark and SE Norway I explain by offshore glacial erosion and no flexural down-bending of the coast.
The geological history of the North Sea Basin during the Quaternary
Dag Ottesen1, Christine Batchelor2, Julian Dowdeswell2 and Helge Løseth3
1Geological Survey of Norway, 2Scott Polar Research Institute, University of Cambridge, 3Statoil ASA
The Quaternary sediments of the central and northern North Sea have been mapped based on a large 2D and 3D seismic database. The Quaternary North Sea basin is a N-S-trending basin, 100-200 km wide and up to 1000 m deep. The infill pattern of the basin is outlined and the depositional setting has been studied based on buried surfaces in 3D seismic cubes. The central basin is filled in by a thick, deltaic sequence deposited from the E-SE, whereas the northern basin is filled in by prograding glacigenic debris flows deposited from the east.
On top of the sediments mapped in the northern basin, west of the Norwegian Channel, an upper regional unconformity (URU) is present. This unconformity is defined by a shift from westward (below) to eastward (above) dipping reflectors, recording a major change in sedimentation (before and after the onset of the formation of the Norwegian Channel). The age of the URU is uncertain, but a timing of around 0.8 million years is suggested. Parts of the sedimentary sequence have been linked to the seismic stratigraphy on the Dutch shelf, which is dated based on palaeo-magnetic and biostratigraphic data (Kuhlmann and Wong, 2008).
The tunnel valleys of the central and northern North Sea (56°N – 62°N): Distribution, Characteristics and Generations
Dag Ottesen1, Margaret Stewart2 and Marco Brønner1
1Geological Survey of Norway, 2British Geological Survey
Tunnel valleys are km-scale linear landforms formed subglacially beneath large ice sheets. In the British and Norwegian sectors of the North Sea, offshore tunnel valleys are associated with multiple Quaternary glaciations. In this study, we use 2D and 3D seismic reflection data, and magnetic data, to map more than a thousand buried tunnel valleys in the central and northern North Sea. The tunnel valleys are generally present from the seabed to depths of around 400 metres, in a study area of 180 000 km2 from 56°N to around 62°N. Buried tunnel valleys are well-imaged in seismic reflection data, particularly in horizontal timeslices in 3D seismic data. In magnetic data, the tunnel valleys appear as small scale magnetic lows, likely due to their infill being less compacted and potentially more porous than the surroundings.
This work provides the most extensive study of tunnel valleys in the region to date, with more than 20% of the study area containing buried tunnel valleys, and also finds the longest tunnel valley recorded worldwide, with large meandering tunnel valleys extending for more than 160 km. We also find tunnel valleys further north than previously reported, as well as a number of isolated tunnel valleys extending towards and into the Norwegian Channel. As reported by other studies in the region, the apparently extensive networks of buried valleys are found to be comprised of cross-cutting generations. In four study areas, we find between 3 and 6 generations, and relate them to potential ice sheet configurations.
Quaternary depositional environments and glacial history of the North Sea constrained by aminostratigraphy
Benedict Reinardy1, Hans Petter Sejrup2 and Berit Hjelstuen2
1Stockholm University, 2University of Bergen
The aminostratigraphy of up to 1000 m of glacial and interglacial sediments in the North Sea Basin is compiled from multiple boreholes sites and dated using strontium isotope (Sr) analysis to provide a chronological framework extending throughout the Quaternary. The new relative and absolute chronology also ties to regional seismostratigraphy. Increasing sediment deposition rate during the Early Pleistocene reflects glacier ice advancing to the Norwegian coast. The earliest evidence of grounded ice in the investigated area comes from mega scale glacial lineations formed during the Mid Pleistocene Transition. At least one episode of diminished coarse clasts and increased foraminiferal diversity during the Mid Pleistocene suggests a progression from ice proximal to warmer, possibly interglacial conditions. Furthermore, the stratigraphically deepest generation of tunnel valleys may have formed during the Mid Pleistocene. Amino acid ratios indicate that a high shear strength till containing chalk clasts transported from the west and/or south of the study area was likely deposited during MIS6. The Late Pleistocene stratigraphy is dominated by glacimarine sediments and tills that are chronologically well constrained with amino acid data. A sand layer recovered at core top in part of the study area is interpreted to correspond to the drainage of an ice-dammed lake in the southern North Sea during the last deglaciation (MIS2). This study shows that much of the Quaternary age sediments within the northern North Sea were deposited relatively rapidly during short periods of time probably leaving significant hiatuses within the stratigraphic record.
Near-shore seafloor depressions in the Western Limfjord, Denmark – potential geohazards?
Anders Dahlin1, Katrine Juul Andresen1, Kasper U. Kjeldsen2, Hans Røy2 and Marit-Solveig Seidenkrantz3
1SeisLab Aarhus, Department of Geoscience, Aarhus University, 2Centre for Geomicrobiology, Department of Bioscience, Aarhus University, 3Centre for Past Climate Studies, Department of Geoscience, Aarhus University
Pockmarks which are circular to semi-circular seafloor depressions formed due to fluid venting, is a well-known geological phenomenon that in several cases have proven to represent geohazards particular in relation to safety and cost implications for the integrity of seafloor constructions and pipelines. During the venting, fine-grained sediment is removed from the venting site leading to an excavation of the seafloor.
In this study, we present preliminary observations of 7 large-scale seafloor depressions in the shallow waters (<20m) of the western Limfjord, Denmark. The depressions are tentatively interpreted as pockmarks and have been mapped using a new multibeam and high-resolution 2D seismic subbottom profiler survey and sediment cores acquired during the WesternLimfjord research expedition in May 2017. The depressions are characterized by a complex circular to elongated map view morphology, a width of 40-500 m, and typical depths of ca. 3 m with very steep sides (11°) and flat to rugged bottom morphologies. In total, the depressions cover an area of roughly 425.000 m2 and can be associated with the removal of ca. 850.000 m3 of sediment, which may have taken place through violent fluid expulsions or slow seepage.
If the depressions are indeed pockmarks they would represent a rare case of near-shore pockmarks which is very important to study in order to constrain their formation, timing, duration and present-day activity and to understand their potential geohazard risk; particularly whether similar structures may form in the future.
Morphology of the southeast Skagerrak (Denmark) from a new geophysical dataset
Matthew Owen1, Zyad Al-Hamdani1, Jørn Jensen1, Jørgen Leth1, Katrine Andresen2 and Lasse Eriksen2
1Department of Marine Geology, Geological Survey of Denmark and Greenland, 2Deparment of Geoscience, Aarhus University
As part of the Danish marine habitat mapping programme an extensive geophysical dataset including multibeam bathymetry, side scan sonar and Innomar sub-bottom profiler has been acquired in the Danish Skagerrak. Approximately 2200 line km of data were acquired in an area of approximately 2600 km2, extending between Skagen in the east and Hirtshals in the west and from 4 m water to 190 m in the deeper Skagerrak some 50 km north of the Danish coast. This new dataset allows the first detailed morphological analysis of this area and the first major study since the mid-1990s. A number of morphological features are noted that both confirm previous observations and provide new insights. In deeper water these include: outcropping strata in the west, where the Jutland current erodes the seabed; sub-parallel wavy Innomar reflectors indicating contourite deposition; grooves eroded into Holocene sequences, showing bottom current pathways; a variety of depression morphologies coupled with a strong gas front indicating gas release and pockmark formation. Where the gas is absent the Innomar signal provides evidence of vertical chimneys and images reflectors previously associated with late Pleistocene ice-proximal glacimarine deposition: below a Holocene sequence tens of metres in thickness. In shallower waters a large variety of bedforms, from ripples to 4 m high sand waves, are present giving strong evidence of the across-shelf sediment transport. These observations have significant implications for seabed habitats, the carbon and sulphur cycle, as well as the region’s glacial history, palaeoclimate and oceanography.
Buried Valleys in the Danish Central Graben
Lasse Krogsgaard Prins1, Katrine Juul Andresen1 and Ole Rønø Clausen1
1SeisLab Aarhus, Department of Geoscience, Aarhus University
The Danish Central Graben has been subject to extensive seismic surveying (both 2D and 3D) during the past four decades. The 3D seismic data has mainly been used for oil and gas exploration, but in the last decade, these data sets have proven very useful for investigating the Quaternary sediments and especially erosional channels. Geotechnical data such as CPTu logs have furthermore proven very successful in determining sediment types and by incorporating geotechnical data we can optimize our geological models and create a geotechnical stratigraphy. In this study, we have utilized both 3D and 2D high-resolution seismic data sets together with geotechnical borehole data to interpret the Quaternary landscape evolution in the Danish North Sea. The emphasis is on the morphology, infill and relative age of buried Quaternary valleys. We describe the differences between the seismic expressions of buried river valleys and tunnel valleys. The present study combines extensive mapping of these channels from 3D seismic data with detailed seismic analyses of high-resolution 2D seismic site surveys in order to validate the mapping from 3D time-slice analyses. This gives us a better understanding of the sediment distribution in the different channels and their relative age. This study is part of the DHRTC (Danish Hydrocarbon Research and Technology Centre)-funded project “Seismic Acoustic Methods: A tool for refining the 3D geotechnical models in a mature hydrocarbon producing area” in which the goal is to create a geotechnical stratigraphy for the Danish Central Graben.
15.4. Open session Marine Geology
EMODnet Seabed Habitat, an ambitious project for mapping benthic habitats in European waters. The Danish contribution.
Zyad Al-Hamdani1, Nicky Witt1 and Matthew Owen
EMODnet (The European Marine Observation and Data Network) is funded by DG-MARE and in its third phase is composed of eight thematic “Portals” aiming at producing a multi-resolution seabed digital map for the whole European waters that include bathymetry, geology, chemistry, biology, physics, human activities, seabed habitat mapping and the recently added Data Ingestion Portal.
The aim of the Seabed Habitat is to produce a broad scale seabed habitat map of all European waters. A cost effective method to obtain full spatial coverage seabed habitat maps uses environmental layers such as sediment types, bathymetry, photic depth etc., as proxy to model the seabed habitat was adopted.
In the Phase I seabed habitat maps were produced with 1km resolution, in Phase II the resolution was increased to 250m and in the current Phase III the aim is to produce 100m resolution broad-scale habitat maps for all European waters. Additionally, individual habitat maps from national surveys and point datasets from national monitoring programs will be collated and standardised (INSPIRE), also habitat distribution models. The final habitat map is converted into EUNIS classification as the common classifier for European waters habitats.
To achieve this member states need to provide available information gathered through mapping endeavours and point sampling.
Denmark has contributed in all EMODnet Phases. We present the latest habitat mapping project performed by GEUS/Orbicon in the North Sea.
When did the Danish/German/Swedish straits form?
Ole Bennike1, Jørn Bo Jensen1 and Niels Nørgaard-Pedersen1
The timing of the formation of the Danish/German/Swedish straits and the first marine influence in the Baltic Basin has been much debated. Here we present new radiocarbon ages from sediment cores retrieved from Danish waters. Most ages are based on shells of marine molluscs, which means that the ages are uncertain because we do not know the reservoir age in the past. We use a reservoir age of 400 years, which is based on dating of museum specimens collected before testing of nuclear bombs starter. It is clear from the ages that the Great Belt (Storebælt) was inundated before the Sound (Øresund). The oldest ages from the northern part of Great Belt are about 8700 cal. years BP. From the central part of the Great Belt the oldest ages are about 8100 cal. years BP and in the south-western Baltic Basin ages varies from 7200 to 7600 cal. years BP. Sediments deposited prior to the occurrence of marine molluscs contain brackish-water ostracodes (Cyprideis torosa and Cytheromorpha fuscata); the sediments are usually laminated and non-bioturbated. The brackish-water phase may have lasted 500 to 1000 years.
EMODnet Geology – a gateway to marine data in Europe
Jørgen O. Leth1, Bjarni Pjetursson1, Matthew J. Owen1 and Zyad Al-Hamdani1
Rapid access to reliable and accurate information is vital in addressing threats to the marine environment, for developing policies and legislation to protect vulnerable marine areas and in understanding trends and forecasting future changes such as the effects of climate change. The access to an effective pan-European marine data infrastructure will also enable effective and efficient marine spatial planning and legislation for environment, fisheries, transport and defence.
The European Marine Observation and Data Network (EMODnet) is a network of more than 160 organisations assembling marine data, products and metadata to make the fragmented resources more available to public and private users relying on quality-assured, standardised and harmonised marine data, which are interoperable and free of restrictions on use. All marine data users including marine industries, decision-making bodies, scientific research and the public in general, benefit from the overall philosophy of the EMODnet data infrastructure “collect once and use many times”.
GEUS has been involved in EMODnet-Geology since the start in 2009. EMODnet-Geology has successfully compiled harmonised offshore data across the European seas including: sea-floor geology, seabed substrates, rates of coastline migration, geological events and probabilities and mineral resources. The products are available via the EMODnet Geology Portal. In its third phase (2017-2020), the existing data products is further developed with higher resolution (1:100.000) including more thematic themes such as, seabed geomorphology and Quaternary and submerged landscapes. New services are being built, so users now can investigate and search for borehole data and seismic survey data using interactive maps and tools.