Katrine J Andresen

The inundated Doggerland in the North Sea Basin has been a coveted research target for many years owing to its key location with respect to geological evolution since the last glaciation and its archaeological potential related to prehistoric hunter–gatherer populations. Still, many uncertainties related to glacial and sea-level forcing on erosion and deposition remain, and the first discovery of submerged settlements is yet to be reported. In this study, we present a range of seismic morphologies and facies characteristic for the late glacial and Holocene succession near a major drainage system at the eastern Dogger Bank. Five of these facies are dominant in the area while two facies can be associated with a terrestrial–fluvial landscape buried 0–22 m below the seafloor. We detect various erosion levels of the terrestrial–fluvial landscape that are greatest towards the south where sediment has been removed, probably owing to combined terrestrial–fluvial and marine erosion. We find that five subareas show geo-archaeological potential in terms of (1) the preservation degree of terrestrial strata based on erosion estimates, (2) the accessibility of terrestrial strata based on burial depths and (3) the palaeolandscape configuration based on the spatial setting in relation to the drainage system and the palaeocoastlines. We further document a geological evolution of the study area, which is comparable with the evolution at the western Dogger Bank. However, we find more evidence for an extended flooding period because of the vicinity to the major drainage system and the Elbe Paleo Valley. We propose that our approach can be used as a workflow for marine investigations that focus on submerged hunter–gatherer heritage.

<p>The STEM (Science, Technology, Engineering and Mathematics) faculties in Denmark suffer from a dearth of women in tenured positions. This is particularly the case for the geosciences in spite of a seemingly equal distribution of men and women graduating in geoscience.</p><p>In this presentation, we highlight the disparities and processes that hinder women from progressing in an academic career in the geosciences in Denmark. We have collected data from Geocenter Denmark that comprises three institutions, Institute for Geoscience, University of Aarhus, Institute for Geoscience and Natural Resources, University of Copenhagen and the Geological Survey of Denmark and Greenland. The data include information on all publications from 2018-2020 including number of publications per researcher, number of (female) authors per publication, impact factor etc. A detailed study has been performed tracking the publication records of all PhD students employed at Geocenter Denmark from<br>2010-2017. Our data also detail the uptake and graduation of undergraduate, masters and PhD students.</p><p>Our results show that for the last 15 years, an equal number of men and women have graduated with a geoscience degree in Denmark. Similarly, on average an equal number of men and women have been awarded a geoscientific PhD degree.</p><p>Analysis of publications from PhD students reveals disparities between genders. Regardless of gender, PhD students publish on average the same number of first author publications during the early years of their career* but male PhD students have more co-authorships. This suggests that female PhD students are not provided with the same opportunities for networking and co-authorship as their male colleagues.</p><p>This disparity continues on all levels, where more than 1/3 of all publications from Geocenter Denmark have no women on the author list. If the first author is male, the number of publications without any female co-authors further increases. Statistically, the chances of obtaining such a high number of publications without female co-authors by random is practically nil. We argue that mechanisms are in place that exclude women from contributing to and co-authoring studies.</p><p>Number of publications is a key factor in academic hireability and can determine success with career progression, funding applications etc. Our data highlight a structural problem in placing a high emphasis on the number of publications.</p><p><br>Disclaimer: Due to lack of data, we consider only binary gender and thus we cannot represent the true<br>non-binary gender diversity.<br>*here defined as up to and including 3 years after PhD graduation.</p>

<p><span>The Greenland ice sheet’s response to anthropogenic warming will have major consequences for global sea levels but its behavior and stability during past warm intervals is poorly known. To elucidate the long-term behavior of the Greenland ice sheet, high-resolution marine records in ice proximal settings are required. Here we report the first results of a study of a deep-water contourite system on the north-east slope Baffin Bay based on geophysical and shallow core data obtained during two marine expeditions in 2017 and 2019. The contourite drift is incised by channels extending from the slope that is build up by prograding ice stream deposits (Melville Bugt trough-mouth fan). As a result, the contourite system presents a complex architecture. While the mechanisms for deposition and erosion are not yet clear, it is likely that the drift accumulated as a result of interactions between a deep contour current and downslope transport of sediments, presumably of glacigenic origin and therefore constitutes an example of an intertwined contourite-turbidite system. A preliminary age-depth model of the trough-mouth fan evolution indicates that the contourite system began to form during the late Early Pleistocene, possibly around 1 million years ago. The contourite drift is a key target for IODP proposal 909, aimed at unravelling the late Cenozoic evolution of the northern Greenland ice sheet and associated changes in Arctic paleoclimate. Shallow sediment cores from this target area have been retrieved and will be analyzed to generate high-resolution multi-proxy records of ocean circulation and sea-surface conditions including sea ice and paleoproductivity for the late Quaternary-Holocene. </span></p>

This study describes a new type of pockmark association from the Lower Congo Basin offshore West Africa, consisting of up to 8 stacked paleopockmarks separated by intervals of drape and onlap fill. The stacked paleopockmarks occur within the depocentres of polygonally-faulted Plio-Pleistocene sediments and are distributed evenly in the downslope parts of two salt mini-basins. The majority of the stacked

The North Sea Basin is considered data rich and well understood. Half a century of oil exploration and research has resulted in a world-class hydrocarbon province, but the Cenozoic succession still contains many poorly understood structures and deposits. The economically most important of these is arguably the occurrence of numerous oilfields hosted within remobilized and injected sandstones, totalling 100s-1000s of km3 of sand showing geometries typical of igneous intrusions. The occurrence of injected sands in the North Sea has been known for about 2 decades and their significance is steadily gaining recognition among North Sea explorers who recognise the reservoir and trap potential of injected sands and their significance as migration and leakage paths. Meanwhile, researchers are bewildered as to the underlying mechanisms leading to repeated and basin-wide remobilization of such large quantities of sand. This paper documents the stratigraphy, distribution and geometrical characteristics of injected sand occurrences in the North Sea. Seismic-scale sand injectites can be subdivided into those that are visibly attached to their parent sandbody and those that are detached from their parent sand. In all cases, seismic-scale sand injectites form inclined sheets, typically at 15-45 degrees relative to their host strata and between 100-300 m in height.

The size of the last glacial ice sheet on the Northeast (NE) Greenland shelf and its interaction with ocean circulation have been the subject of debate. Here we provide insights into the extent of the ice sheet around the Last Glacial Maximum (LGM) and investigate timing and strength of changes in the flow of Atlantic Water. The study is based on a multiproxy investigation of a marine sediment core, gravity core DA17‐NG‐ST01‐019G, from 323‐m water depth at the NE Greenland shelf edge at 79.4°N. We present benthic and planktic foraminiferal distribution data, AMS‐14C dates, sedimentological (ice‐rafted debris (IRD) and grain sizes), and geochemical (XRF) data in combination with geophysical (sub‐bottom profiler) data. The oldest sediments at the study site are dated to 25.5–17.5 ka, encompassing the time frame from the beginning of the LGM to the early deglaciation. This part is overlain by sediments from the late deglaciation and Holocene. The deposits dating from the LGM are very r...

The spatial extent and quality of seismic and subsurface datasets have substantially improved in recent years due to traditional hydrocarbon activities and the emergence of green technologies like offshore wind. This Special Publication investigates the opportunities for (re)investigating past environments using seismic geomorphology and its integration with other datasets.

A reflection seismic survey has been carried out in Vejle fjord in Denmark in order to map the thickness of organic rich gyttja sediments. The reflection seismic data was severely contaminated by multiples and suffered from high absorption in the near surface sediments. Consequently, a direct and reliable interpretation of gyttja in the entire survey area could not be accomplished. Alternatively, the interpretation has been based on the pull-down effect on reflections which in the present case is the only way to achieve a coherent estimate on sediment thicknesses. Borehole information has been used to estimate the velocity in the gyttja layer.

Dedicated Fluids and fluid flow This study presents sandstone intrusions and fluid migration from the Eastern North Sea area south of the Siri Canyon and east of the Central Graben and thereby introduces possible new hydrocarbon plays in a hitherto underdeveloped area. Two sets of intrusions are recognized. The first set is represented by conical to tabular high-amplitude cross-cutting reflections within the Oligocene succession above the Ringkbing Fyn-High. The second set is recognized in the Eocene succession north of the D-1 fault. The intrusions in both areas are associated with a pronounced forced-folded surface onto which onlaps are observed. The onlaps and the forced-folded surfaces indicate that intrusion took place c. 25 Ma in the first area and c. 34 Ma in the second area. The suggested model of generation for the intrusions involves remobilization of source sand units within the Paleocene to Eocene succession due to overpressure build-up facilitated mainly by differential loading and influx of fluids from the deeper successions. The study thus highlights the impact of differential loading on sand remobilization and furthermore describes potential fluid migration from a deep thermogenic source located in the Ringkbing-Fyn High area.

Summary Result from two 3D seismic surveys acquired in inner Danish shallow water in May 2017 are presented. One survey was acquired south of the island of Anholt in cooperation with the Geological Survey of Denmark and Greenland (GEUS) and the other survey was acquired in Limfjorden (Visby Bredning). Both survey areas are located in shallow waters (< 30 m) and acquisition was carried out from Aarhus University’s research vessel Aurora. The P-cable 3D seismic acquisition system has been applied in both surveys. This system was recently introduced at the Department of Geoscience, Aarhus University and is presently being adapted to our survey capabilities.

The Little Belt strait in the inner Danish waters is characterised by a high biodiversity, and continuous monitoring of flora and fauna and the water quality is undertaken by the authorities. However, the surface sedimentology and geomorphology, i.e. elements of the geodiversity, are less well-constrained. The aim of this study is to investigate the surface sediment and morphology of a large meander bend (with a channel width of ∼1 km) located between the two bridges crossing the strait (a channel reach of ∼4 km) in order to assess a potential coupling between geodiversity and biodiversity. More specifically, the objectives are 1) to identify and classify morphological units for creating a geomorphological map, 2) to quantify surface material characteristics for creating a surface material map, and 3) to develop a conceptual model of the substrate and the morphology and morphodynamics in the meander bend between the two bridges in the strait. Preliminary results reveal a diverse mor...

In this study we investigate the source rock maturity of the organic-rich Upper Jurassic Farsund and Lola formations in the southern Danish Central Graben. We do this by analyzing an interval velocity volume derived through seismic processing flows for discrete low-velocity anomalies occurring within the source rock succession. We have mapped the anomalies and calibrated them with source rock data within several wells in the study area. Although not unambiguous, our results indicate that some of the low-velocity anomalies potentially can be ascribed to variations in source rock composition and maturity, and hydrocarbon generation. Two critical steps are to 1) quality-check the utilized interval velocity volume i.e. rule-out any geophysical effects and artefacts and 2) calibrate the mapped low-velocity anomalies to source rock effects i.e. rule-out effects from other geological features such as lithological variations, porosity-permeability fluctuations, diagenesis, anisotropy, overpressure and clay content. Besides of using information from well logs and laboratory measurements on core and drill cuttings samples, calibration is based on utilizing seismic attributes and fluid flow features which address the overall migration routes in the conventional hydrocarbon plumbing system of the study area.

Abstract Pockmarks or crater-like depressions formed due to fluid venting, is a well-known geological phenomenon. On a global scale, pockmarks expel a significant amount of fluids and greenhouse gasses to the marine environment and the atmosphere. Despite pockmarks being well-studied, the longevity and history of activity are rarely addressed. In this study, we analyse more than twenty nearshore seafloor depressions of varying morphology and size in the shallow waters of the western Limfjord in northern Denmark. By using high-resolution seismo-acoustic and sediment core data, we characterize the morphology and sediments of the pockmarks. We further use 14C-dating and pore water analyses to address the timing and activity of the depressions. Our results show that the depressions coincide with submarine groundwater discharge areas and hence represent freshwater pockmarks. The pockmarks most likely formed initially due to two eruptive events of thermogenic light oil/gas ca. 2000 and 900 yrs. BP, both triggered by relative sea-level fall. Freshwater seepage continues to sustain and develop the pockmark morphology and we show that pockmarks grow by collapse of pockmark walls and amalgamation of discrete erosive seepage sites at the bottom. The episodic expulsions of thermogenic fluids and the continuous seepage of freshwater probably prolonged the longevity of the studied pockmarks and further demonstrates the complex nature of pockmark formation and activity. While thermogenic and biogenic gas escape to the surface, on the global scale, is relevant for the greenhouse gas budget, the outflow of groundwater which may or may not be polluted is relevant with respect to the geochemistry, biota and productivity of the receiving marine environment especially in shallow water settings.

Abstract This study uses 3D seismic mapping, NNCC attribute analysis and 2D SDEM modelling of soft-sediment deformation to analyse hanging wall deformation related to faulting across a listric fault detaching along the top of a major salt roller. The computational model experiments used the overall fault and salt-structure evolution as boundary conditions to predict the distribution of faults within the hanging wall. The modelling successfully reproduced geometries similar to the syn- and antithetic faults that are visible on seismics, but it also showed the presence of well-defined vertical deformation zones, both in the hanging wall and the foot-wall of the listric fault. In the model, salt movement controls the formation of the deformation zones. The similarity of NNCC-inferred vertical chimneys and the modelled deformation zones suggests that the subtle vertical chimneys identified in the 3D seismic data might actually be related to vertical to sub-vertical deformation zones caused by the presence and movement of the salt structure.

Subsurface fluid migration is an essential process in sedimentary basins and is critical for the charging of hydrocarbon reservoirs. Observations of direct hydrocarbon indications and other geological and geophysical features indicative of fluid migration such as shallow gas, pockmarks, gas chimneys, pipes and velocity effects, all record past and/or present fluid migration. The specific migration routes are however often difficult to address in detail and thus typically represent a key unknown factor in studies of hydrocarbon plumbing systems. In this study, we present a detailed 3D-seismic analysis of shallow gas anomalies occurring in relation to a listric fault detaching on top of an elongated salt structure in the eastern North Sea. A neural-network-trained chimney-cube has been applied on the dataset allowing us to unravel the migration routes for the shallow gas anomalies and to understand the development of the gas accumulations in relation to the structural evolution of the listric fault and underlying salt structure. The shallow gas is thus suggested to be linked with deep and possibly thermogenic fluid migration and to be highly dependent on the sealing properties of the listric fault which is observed to be permeable in its lower part and sealing in its upper part.

The present focusses are on the Balakhany and Pereriva Suites of the Productive Series over the Umid Babek structural trend within Baku Archipelago, since these are considered to be the most prospective in terms of hydrocarbon reserves potential.

This study presents a seismo-stratigraphic framework for the late Quaternary to Holocene succession in the Southern Danish Central Graben based on unit mapping and characterization from a combination of geophysical, geological and geotechnical data. The mapped units are constrained by erosional surfaces associated with both glacial, marine and fluvial erosion and hence record major events in the central North Sea Basin.

During August 2017, as part of the habitat mapping of Natura2000 areas, a geophysical survey of a large area within the Skagerrak was undertaken by the Geological Survey of Denmark and Greenland. In this article, we use the acquired data to discuss the geology of Tannis Bugt (Fig. 1), a large shallow bay at the north-west coast of Vendsyssel. The bay extends 40 km between Hirtshals in the west and Skagen in the east forming the northern-most Danish Skagerrak coast.

<p>The Greenland Ice Sheet (GIS), the second largest ice sheet on Earth, has experienced a dramatic ice mass reduction during the last decades, coincident with global warming and an increase in atmospheric CO<sub>2</sub>. About 16% of the GIS is currently drained via marine terminating glaciers, mostly through the Northeast Greenland Ice Stream (NEGIS; with ~12%). Two cross-shelf troughs (Norske and Westwind troughs) served as drainage pathways of the NEGIS. According to numerical ice-sheet models, a whole meltdown of the GIS may cause a global sea−level rise of >7 m, causing permanent damage to the environment and countless economic impacts on our coastal society. In order to better understand the processes driving these present changes, studies of the development of glaciers/glacial troughs and ice sheets in response to past climate changes are required for testing numerical models that seek to predict ice-sheet response to anthropogenic climate change.</p><p>In this study, high-resolution INNOMAR sediment subbottom profiler data combined to multi-proxy analyses of gravity core DA17-NG-ST10-117G, obtained from Norske Trough during the NorthGreen17 expedition, are investigated. Multi-proxy data derived from the sediment gravity core include <sup>14</sup>C-derived ages, descriptions of sedimentary units, compositional variability of ice-rafted debris, and continuous logging of magnetic susceptibility and micro-XRF core scanning. In Norske Trough, submarine glacial landforms indicate that ice sheet retreat to the outer middle shelf after the Last Glacial Maximum (LGM) was stepwise, with phases of grounding line stabilization, while ice sheet retreat from the middle shelf to the coastline during deglaciation was fast. Sedimentological evidence at our recorded coring site captures the transition from sub–ice stream (subglacial) environments to proximal (proglacial)/distal glaciomarine conditions during the LGM to Holocene recession. In addition, preliminary foraminifera analysis indicates warmer recirculating Atlantic Water on the middle Norske Trough immediately on deglaciation, suggesting that oceanic forcing very likely played a significant role during the retreat of the ice margin. This presentation will include a comprehensive comparison of the spatio-temporal sedimentation patterns across the Norske Trough.</p>

This study presents the first detailed and integrated mapping of buried Quaternary valleys, river systems and iceberg scourings from the Danish North Sea region. The mapped features coincide spatially but have very different characteristics and incision levels which allow us to constrain their relative timing and differentiate their environment of formation (subglacial, proglacial and marine). The results of the study bring new critical information regarding the paleoenvironment of the North Sea Basin during the latest Quaternary deglaciation period and our analysis provide a well-tested workflow for utilizing 2D and 3D seismic data in relation to paleogeographical reconstructions.

This study presents the first detailed and integrated mapping of buried Quaternary valleys, river systems and iceberg scourings from the Danish North Sea region. The mapped features coincide spatially but have very different characteristics and incision levels which allow us to constrain their relative timing and differentiate their environment of formation (subglacial, proglacial and marine). The results of the study bring new critical information regarding the paleoenvironment of the North Sea Basin during the latest Quaternary deglaciation period and our analysis provide a well-tested workflow for utilizing 2D and 3D seismic data in relation to paleogeographical reconstructions.

ABSTRACT The Top Pre Zechstein (TPZ) surface in the North Sea Basin is often mapped because it reveals the total basement tectonics in the area. In areas where Zechstein salt is present halokinetic processes, differential subsidence, and Mesozoic faulting however significantly alter the TPZ surface. The study area is located at the southern margin of the Northern Permian Basin in the eastern North Sea at the northern flank of the Ringkøbing-Fyn High. This area occurs approximately at the pinch-out line of the late Permian Zechstein salt and constitutes an excellent theater illustrating a range of salt-related problems. The TPZ surface is characterized by an overall NNW-ward dip defining the northern flank of the RFH and is transected by a set of NNW-SSE striking faults, and a E-W striking set of minor faults. Salt structures in the northern part of the study area introduce velocity pull-up (artefacts) at the TPZ surface and furthermore cause intense faulting of the Mesozoic and Cenozoic cover sediments. Pronounced isolated topographic highs similar to hills can be observed in the southern part of the study area where no to very little Zechstein evaporites are present. In the central part where Zechstein evaporites are present, small topographic highs similar to ridges can be observed at the footwall crest of minor faults. The Zechstein evaporites generally onlap towards the south in the study area but in the transitional zone around the hills, onlap from all directions onto the hills is observed. This suggests that the hills reflect paleo-topography developed during sub-aerial exposure before and perhaps during the deposition of the Zechstein sediments. The internal reflections within the hills show that they are composed of southward dipping sediments and very evident erosional truncations can be observed. The hills are aligned parallel to the major E-W striking basement fault, but are not directly associated to faults offsetting the TPZ surface. However, the alignment, the dipping of the strata which are exposed in the hills, and the similar seismic signature of the strata exposed in the hills indicate that the hills are remnants of a footwall high which is progressively eroded from the north. The ridges are associated with minor faults offsetting the TPZ surface, but more importantly the internal reflections within the ridges resemble those of Zechstein carbonate reefs observed in the southern Permian Basin. The lateral distribution of the Zechstein facies and the adjacent land topography show that the topography at the TPZ surface was generated before and during the Zechstein due to faulting and relative uplift of footwalls. The footwall crests of minor faults constituted when flooded, areas with lesser water depth and consequently display different sediment facies. The study thus demonstrates a unique and detailed insight into the TPZ paleogeography which has significant implications for the understanding of the geological development in the eastern North Sea Basin, and may be of importance during the evaluation of the future hydrocarbon potential of the eastern North Sea Basin.

ABSTRACT This study describes remobilized Paleogene sand occurring on the hanging-wall segment north of the major D-1 normal fault in the Norwegian-Danish Basin, eastern North Sea. The remobilized sand is observed on 3D seismic data in fine-grained Eocene host-strata as cross-cutting reflections with a typical tabular, V-shaped or wing-like geometry in the seismic cross-sections and a pronounced jack-up of the overlying succession onto which onlap can be observed. In map view the remobilized sand in certain areas have a channel-like appearance. The seismic observations indicate that the sand has a remobilized origin which may be partly depositional. Particularly the observed wings and jack-up on the seismic cross-sections indicate remobilization which potentially could be generated by two different processes: a) remobilization of depositional channel sand resulting in the formation of injected wings along the sides of the channel, or b) injection of remobilized sand from the deeper Paleocene strata causing jack-up and typically V-shaped intrusions. Injection of Paleocene sand into Eocene host strata is a well-known phenomenon from the nearby Paleogene Siri Canyon located c. 15 km north of the study area. In order to acquire more information about the intrusions a geochemical study and a detailed biostratigraphical dating of cuttings and sidewall core samples from the Floki-1 well was carried out. The Floki-1 well penetrates the remobilized sand and was drilled to test an apparent 4-way closure on prospect Eocene sand which by then was interpreted to be 100 % depositional. The geochemical study of the samples from the sand identified the Floki-sandstone as a very fine grained sand and silt with a matrix of very angular silt grains. The sand does not contain clays. The matrix appears to have formed by crushing of the sand grains. Thus, heavy minerals appear to have disintegrated by crushing but still most parts of the mineral grain is found together. Glauconite grains are strongly smeared. The sorting pattern, and the angular shape of silt sized matrix grains, and the intense shearing and deformation of glauconite grains indicates that the sand may have been injected under high pressure, resulting in massive crushing of detrital grains. The age dating mainly includes dinocysts analysis from seven sidewall core samples and nine cutting samples above, within and below the sand. It is expected that the sand should either be of Eocene age probably revealing a depositional origin with subsequent remobilization to the sides (process a), or a Paleocene age revealing injection from the deeper strata (process b). In order to address all observations, a potential model of generation may include elements of depositional sand combined with up-, downward and/or lateral injection which could have been facilitated by intense activity in the nearby D-1 fault. The study highlights the importance of interdisciplinary approaches in the interpretation of complex geological features formed by several geological processes and mechanisms.

A mounded structure has been observed in the Norwegian-Danish Basin about 10 km east of the Coffee Soil Fault outside the Central Graben and almost directly on top of the mid-Miocene unconformity. The mounded structure has been mapped using 3D seismic data; it consists of two culminations arranged in a triangular area; one is 1500 m long, 800 m wide and 70 m high while the other is 800 m long, 400 m wide and 30 m high. The composite mound comprises a volume of some 29 mio m3 and is characterised by a high positive reflection amplitude at the top, differential compaction as compared to the surrounding sediments and velocity pull up in underlying reflections. These observations indicate a high velocity fill with higher acoustic impedance and less compaction than that of the surrounding sediments, and the interior of the mounded structure has thus been interpreted as a relatively hard, coarse grained or well cemented sediment. The observed mound is an isolated feature and there have be...

... Katrine J. Andresen * , Ole R. Clausen and Rune B. Jørgensen Department of Earth Sciences, Aarhus University, Høegh-Guldbergs Gade 2, DK-8000 Aarhus C, Denmark. *Corresponding author (e-mail: katrine.andresen{at}geo.au.dk). Abstract. ...