The Palaeogene volcanic succession in the northern part of the Nuussuaq Basin in West Greenland comprises three formations: the Vaigat and Svartenhuk Formations of Paleocene age (61–58 Ma) and the Naqerloq Formation of Eocene age (57–54 Ma). In this study, we formalise and describe the volcanic stratigraphy on Svartenhuk Halvø and the areas with lavas that flowed across the basin boundary onto the adjoining basement areas in the north and east. The Vaigat Formation comprises three members. The Kakilisaat and Nerutusoq Members are of minor volume and consist of, respectively, crustally contaminated basalts and chemically enriched basalts with relatively high contents of incompatible trace elements. They are overlain by the voluminous Nunavik Member of tholeiitic picrites (MgO ≥12 wt%) and subordinate magnesian basalts. The oldest volcanic deposits are commonly foreset-bedded hyaloclastites, and the overlying subaerial lavas are mainly thin, grey, crumbling flows. Eruption sites were mainly within the basin, with depocentres in the south and hyaloclastite and lava transport directions towards the north. Thicknesses vary from up to at least 2000 m in the south to ≥380 m in the northernmost exposures close to 72°N. The Svartenhuk Formation comprises four members. The lowest, Kuugaartorfik Member, is up to 100 m thick and consists partly of quartzofeldspathic and partly volcanogenic sediments; it is restricted to northern Svartenhuk Halvø and the Innerit peninsula. The overlying volcanic Tunuarsuk, Nuuit and Skalø Members are voluminous and widespread, with a combined thickness of up to 1800 m. They consist of tholeiitic basalts with similar chemical compositions but with correlatable stratigraphic variation patterns. The Tunuarsuk Member consists of interspersed flow groups of thin, grey flows and massive, brown flows; the Nuuit Member comprises mainly massive brown flows, and the Skalø Member is dominated by light grey flows. The Svartenhuk Formation oversteps the Vaigat Formation on the basement in the north and east. In these distal areas the Tunuarsuk and Nuuit Members constitute the major volumes, and preserved thicknesses are up to 1400 m. In northern and eastern Svartenhuk Halvø and also farther to the north and east, foreset-bedded hyaloclastites indicate transport directions towards the north and possibly east from eruption sites within the basin. The Naqerloq Formation comprises one member, the Arfertuarsuk Member, consisting of flows of brown basalt with relatively enriched chemistry and a single trachyte flow. The member is only found in western Svartenhuk Halvø and on Skalø, where it conformably overlies the older lavas with up to 350 m thickness preserved after erosion. Dykes of all three formations are present. The distribution of dykes of the Naqerloq Formation suggests that this originally extended much farther east. Picrites and basalts of the Vaigat and Svartenhuk Formations are geochemically related; the picritic lavas represent e
{"title":"Lithostratigraphy, geology and geochemistry of the Tertiary volcanic rocks on Svartenhuk Halvø and adjoining areas, West Greenland","authors":"J. G. Larsen, L. Larsen","doi":"10.34194/geusb.v50.8295","DOIUrl":"https://doi.org/10.34194/geusb.v50.8295","url":null,"abstract":"The Palaeogene volcanic succession in the northern part of the Nuussuaq Basin in West Greenland comprises three formations: the Vaigat and Svartenhuk Formations of Paleocene age (61–58 Ma) and the Naqerloq Formation of Eocene age (57–54 Ma). In this study, we formalise and describe the volcanic stratigraphy on Svartenhuk Halvø and the areas with lavas that flowed across the basin boundary onto the adjoining basement areas in the north and east. The Vaigat Formation comprises three members. The Kakilisaat and Nerutusoq Members are of minor volume and consist of, respectively, crustally contaminated basalts and chemically enriched basalts with relatively high contents of incompatible trace elements. They are overlain by the voluminous Nunavik Member of tholeiitic picrites (MgO ≥12 wt%) and subordinate magnesian basalts. The oldest volcanic deposits are commonly foreset-bedded hyaloclastites, and the overlying subaerial lavas are mainly thin, grey, crumbling flows. Eruption sites were mainly within the basin, with depocentres in the south and hyaloclastite and lava transport directions towards the north. Thicknesses vary from up to at least 2000 m in the south to ≥380 m in the northernmost exposures close to 72°N. The Svartenhuk Formation comprises four members. The lowest, Kuugaartorfik Member, is up to 100 m thick and consists partly of quartzofeldspathic and partly volcanogenic sediments; it is restricted to northern Svartenhuk Halvø and the Innerit peninsula. The overlying volcanic Tunuarsuk, Nuuit and Skalø Members are voluminous and widespread, with a combined thickness of up to 1800 m. They consist of tholeiitic basalts with similar chemical compositions but with correlatable stratigraphic variation patterns. The Tunuarsuk Member consists of interspersed flow groups of thin, grey flows and massive, brown flows; the Nuuit Member comprises mainly massive brown flows, and the Skalø Member is dominated by light grey flows. The Svartenhuk Formation oversteps the Vaigat Formation on the basement in the north and east. In these distal areas the Tunuarsuk and Nuuit Members constitute the major volumes, and preserved thicknesses are up to 1400 m. In northern and eastern Svartenhuk Halvø and also farther to the north and east, foreset-bedded hyaloclastites indicate transport directions towards the north and possibly east from eruption sites within the basin. The Naqerloq Formation comprises one member, the Arfertuarsuk Member, consisting of flows of brown basalt with relatively enriched chemistry and a single trachyte flow. The member is only found in western Svartenhuk Halvø and on Skalø, where it conformably overlies the older lavas with up to 350 m thickness preserved after erosion. Dykes of all three formations are present. The distribution of dykes of the Naqerloq Formation suggests that this originally extended much farther east. Picrites and basalts of the Vaigat and Svartenhuk Formations are geochemically related; the picritic lavas represent e","PeriodicalId":48475,"journal":{"name":"Geus Bulletin","volume":" ","pages":""},"PeriodicalIF":1.7,"publicationDate":"2022-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47011061","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
W. Colgan, H. J. Henriksen, O. Bennike, Sofia Riberio, M. Keiding, Ida Karlsson Seidenfaden, M. Graversgaard, A. Busck, M. Fruergaard, M. Knudsen, J. Hopper, T. Sonnenborg, Maria Rebekka Skjerbæk, A. Bjørk, H. Steffen, L. Tarasov, R. S. Nerem, K. Kjeldsen
We present the most recent Intergovernmental Panel on Climate Change Sixth Assessment Report (AR6) sea-level projections for four Danish cities (Aarhus, Copenhagen, Esbjerg and Hirtshals) under the Shared Socioeconomic Pathway (SSP) family of climate scenarios. These sea-level changes projected over the next century are up to an order of magnitude larger than those observed over the previous century. At these cities, year 2150 sea-level changes of between 29 and 55 cm are projected under the very low emissions scenario (SSP1-1.9), while changes of between 99 and 123 cm are projected under the very high emissions scenario (SSP5-8.5). These differences highlight the potentially significant impact of remaining opportunities for climate change mitigation. Due to this increase in mean sea level, the mean recurrence time between historically extreme events is expected to decrease. Under the very high emissions scenario, the historical 100-year storm flood event will become a 1- to 5-year event at most Danish harbours by 2100. There is considerable uncertainty associated with these sea-level projections, primarily driven by uncertainty in the future evolution of the Antarctic ice sheet and future sterodynamic changes in ocean volume. The AR6 characterises collapse of the West Antarctic ice sheet as a low-probability but high-impact event that could cause several metres of sea-level rise around Denmark by 2150. In climate adaptation policy, the scientific landscape is shifting fast. There has been a tremendous proliferation of diverse sea-level projections in recent years, with the most relevant planning target for Denmark increasing c. 50 cm in the past two decades. Translating sea-level rise projections into planning targets requires value judgments about acceptable sea-level risk that depend on local geography, planning timeline and climate pathway. This highlights the need for an overarching national sea-level adaptation plan to ensure municipal plans conform to risk and action standards.
{"title":"Sea-level rise in Denmark: paleo context, recent projections and policy implications","authors":"W. Colgan, H. J. Henriksen, O. Bennike, Sofia Riberio, M. Keiding, Ida Karlsson Seidenfaden, M. Graversgaard, A. Busck, M. Fruergaard, M. Knudsen, J. Hopper, T. Sonnenborg, Maria Rebekka Skjerbæk, A. Bjørk, H. Steffen, L. Tarasov, R. S. Nerem, K. Kjeldsen","doi":"10.34194/geusb.v49.8315","DOIUrl":"https://doi.org/10.34194/geusb.v49.8315","url":null,"abstract":"We present the most recent Intergovernmental Panel on Climate Change Sixth Assessment Report (AR6) sea-level projections for four Danish cities (Aarhus, Copenhagen, Esbjerg and Hirtshals) under the Shared Socioeconomic Pathway (SSP) family of climate scenarios. These sea-level changes projected over the next century are up to an order of magnitude larger than those observed over the previous century. At these cities, year 2150 sea-level changes of between 29 and 55 cm are projected under the very low emissions scenario (SSP1-1.9), while changes of between 99 and 123 cm are projected under the very high emissions scenario (SSP5-8.5). These differences highlight the potentially significant impact of remaining opportunities for climate change mitigation. Due to this increase in mean sea level, the mean recurrence time between historically extreme events is expected to decrease. Under the very high emissions scenario, the historical 100-year storm flood event will become a 1- to 5-year event at most Danish harbours by 2100. There is considerable uncertainty associated with these sea-level projections, primarily driven by uncertainty in the future evolution of the Antarctic ice sheet and future sterodynamic changes in ocean volume. The AR6 characterises collapse of the West Antarctic ice sheet as a low-probability but high-impact event that could cause several metres of sea-level rise around Denmark by 2150. In climate adaptation policy, the scientific landscape is shifting fast. There has been a tremendous proliferation of diverse sea-level projections in recent years, with the most relevant planning target for Denmark increasing c. 50 cm in the past two decades. Translating sea-level rise projections into planning targets requires value judgments about acceptable sea-level risk that depend on local geography, planning timeline and climate pathway. This highlights the need for an overarching national sea-level adaptation plan to ensure municipal plans conform to risk and action standards.","PeriodicalId":48475,"journal":{"name":"Geus Bulletin","volume":"1 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2022-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41806888","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The aim of this study is to elucidate the character of the earliest phases of Jurassic rifting in North-East Greenland. To achieve this, detailed sedimentological analysis and geological mapping were undertaken on the outcrops of central Kuhn Ø (74°53’55’’N,20°20’56”W). In this region the basement is overlain by the fluvial Bastians Dal Formation (Middle Jurassic) which is, in turn, overlain by the coal-bearing Muslingebjerg Formation. A maximum thickness of 140 m is calculated for the Bastians Dal Formation and mapping of stratal geometries demonstrates thinning to both the north and south, confirming that these deposits infill a palaeovalley. Predominantly south-westward palaeocurrent orientations are observed and likely reflect the orientation of the palaeovalley (NE–SW). The overlying Muslingebjerg Formation displays significant lateral variations in thickness as well as facies, thickening from a 5-m-thick coal seam in the north to 50 m in the south. Southern outcrops include two intervals of fine-grained sandstones displaying low-angle and trough cross-bedding some of which contain suggestions of tidal bundling. The arrangement of facies suggests that coal formation occurred in both fluvial- and shallow-marine (tidal?) environments. Coals are similar to those described elsewhere from the Muslingebjerg Formation and display subtle differences consistent with variable degrees of marine influence. Mapping demonstrates the presence of an NE–SW-oriented bounding fault in the south of the region into which the Muslingebjerg Formation thickens. This likely also controlled the orientation of the underlying NE–SW-aligned palaeovalley and is oblique to the proposed overall N–S orientation of faulting related to rifting through the Mid to Late Jurassic. Instead, these alignments resemble those that define pre-Jurassic phases of rifting and may therefore indicate a transitional phase of tectonism. Faulting on a similar alignment can be traced SW, cutting Lindeman Fjord and following the valleys east of the A. P. Olsen Land plateau.
{"title":"The sedimentology and depositional environments of the Bastians Dal and Muslingebjerg formations: evidence for the earliest phases of Jurassic rifting in North-East Greenland","authors":"S. Andrews, H. Vosgerau, J. Bojesen‐Koefoed","doi":"10.34194/geusb.v49.8311","DOIUrl":"https://doi.org/10.34194/geusb.v49.8311","url":null,"abstract":"The aim of this study is to elucidate the character of the earliest phases of Jurassic rifting in North-East Greenland. To achieve this, detailed sedimentological analysis and geological mapping were undertaken on the outcrops of central Kuhn Ø (74°53’55’’N,20°20’56”W). In this region the basement is overlain by the fluvial Bastians Dal Formation (Middle Jurassic) which is, in turn, overlain by the coal-bearing Muslingebjerg Formation. A maximum thickness of 140 m is calculated for the Bastians Dal Formation and mapping of stratal geometries demonstrates thinning to both the north and south, confirming that these deposits infill a palaeovalley. Predominantly south-westward palaeocurrent orientations are observed and likely reflect the orientation of the palaeovalley (NE–SW). The overlying Muslingebjerg Formation displays significant lateral variations in thickness as well as facies, thickening from a 5-m-thick coal seam in the north to 50 m in the south. Southern outcrops include two intervals of fine-grained sandstones displaying low-angle and trough cross-bedding some of which contain suggestions of tidal bundling. The arrangement of facies suggests that coal formation occurred in both fluvial- and shallow-marine (tidal?) environments. Coals are similar to those described elsewhere from the Muslingebjerg Formation and display subtle differences consistent with variable degrees of marine influence. Mapping demonstrates the presence of an NE–SW-oriented bounding fault in the south of the region into which the Muslingebjerg Formation thickens. This likely also controlled the orientation of the underlying NE–SW-aligned palaeovalley and is oblique to the proposed overall N–S orientation of faulting related to rifting through the Mid to Late Jurassic. Instead, these alignments resemble those that define pre-Jurassic phases of rifting and may therefore indicate a transitional phase of tectonism. Faulting on a similar alignment can be traced SW, cutting Lindeman Fjord and following the valleys east of the A. P. Olsen Land plateau.","PeriodicalId":48475,"journal":{"name":"Geus Bulletin","volume":" ","pages":""},"PeriodicalIF":1.7,"publicationDate":"2022-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48220196","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Carbonate rocks of Neoproterozoic to Silurian age are abundantly distributed around the coasts of North and North-East Greenland. Palaeokarst horizons are particularly well developed within the Portfjeld Formation (Ediacaran – earliest Cambrian) and beneath the Buen Formation (Cambrian Series 2), and there are caves within Ordovician limestones infilled by Caledonian molasse of Middle Devonian age. The youngest karst is a series of caves distributed from Hall Land in western North Greenland to Kronprins Christian Land in eastern North Greenland. Caves within Ordovician carbonates in Freuchen Land are currently the northernmost documented karst caves globally. The caves are mainly open phreatic conduits, any fill that is present is unlithified, and cave collapse is limited to minor breakdown associated with frost shattering. These geologically young caves are consistently located up to a few 100 m beneath the distinctive plateau that characterises the topography of the northern coast, and their identical context suggests that they developed in a single phase of speleogenesis. The caves are exposed where the plateau has been incised by outlet glaciers from the Greenland ice sheet. The timing of cave development in North Greenland is constrained by the mid- to late-Miocene (15–5 Ma) uplift of the plateau surface and the onset of fjord-forming glaciation in the latest Pliocene – earliest Pleistocene (c. 2.7–2.5 Ma). The evidence suggests that phreatic caves in the southern part of North-East Greenland, on C. H. Ostenfeld Nunatak, are of a broadly similar age. The caves of North and North-East Greenland offer a glimpse of large-scale phreatic drainage systems that developed below an uplifted coastal peneplain during Neogene time. They preserve an important part of the geological history of North and North-East Greenland that is otherwise absent from the physical geological record.
{"title":"The karst and palaeokarst of North and North-East Greenland – physical records of cryptic geological intervals","authors":"Paul K. Smith, G. Moseley","doi":"10.34194/geusb.v49.8298","DOIUrl":"https://doi.org/10.34194/geusb.v49.8298","url":null,"abstract":"Carbonate rocks of Neoproterozoic to Silurian age are abundantly distributed around the coasts of North and North-East Greenland. Palaeokarst horizons are particularly well developed within the Portfjeld Formation (Ediacaran – earliest Cambrian) and beneath the Buen Formation (Cambrian Series 2), and there are caves within Ordovician limestones infilled by Caledonian molasse of Middle Devonian age. The youngest karst is a series of caves distributed from Hall Land in western North Greenland to Kronprins Christian Land in eastern North Greenland. Caves within Ordovician carbonates in Freuchen Land are currently the northernmost documented karst caves globally. The caves are mainly open phreatic conduits, any fill that is present is unlithified, and cave collapse is limited to minor breakdown associated with frost shattering. These geologically young caves are consistently located up to a few 100 m beneath the distinctive plateau that characterises the topography of the northern coast, and their identical context suggests that they developed in a single phase of speleogenesis. The caves are exposed where the plateau has been incised by outlet glaciers from the Greenland ice sheet. The timing of cave development in North Greenland is constrained by the mid- to late-Miocene (15–5 Ma) uplift of the plateau surface and the onset of fjord-forming glaciation in the latest Pliocene – earliest Pleistocene (c. 2.7–2.5 Ma). The evidence suggests that phreatic caves in the southern part of North-East Greenland, on C. H. Ostenfeld Nunatak, are of a broadly similar age. The caves of North and North-East Greenland offer a glimpse of large-scale phreatic drainage systems that developed below an uplifted coastal peneplain during Neogene time. They preserve an important part of the geological history of North and North-East Greenland that is otherwise absent from the physical geological record.","PeriodicalId":48475,"journal":{"name":"Geus Bulletin","volume":" ","pages":""},"PeriodicalIF":1.7,"publicationDate":"2022-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44028166","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Despite more than a century of investigations, parts of the Quaternary stratigraphy of Denmark with their fragmented record of deposits remain ambiguous. Here we describe a newly found interglacial clay deposit from Ejby on Sjælland, Denmark, from a borehole at 55.695°N, 11.839°E (terrain elevation 5.7 m above sea level). We place the new occurrence on record and provide details of the macrofossil analysis of the sample. The clay contains remains of the present-day temperate bivalve Corbicula fluminalis and the caddis fly Hydropsyche contubernalis – both inhabiting rivers. The presence of C. fluminalis indicates that the deposit most probably is of Middle Pleistocene age, older than the last interglacial, the Eemian.
{"title":"A new Middle Pleistocene interglacial occurrence from Ejby, Sjælland, Denmark","authors":"O. Bennike, P. Wiberg‐Larsen","doi":"10.34194/geusb.v49.8294","DOIUrl":"https://doi.org/10.34194/geusb.v49.8294","url":null,"abstract":"Despite more than a century of investigations, parts of the Quaternary stratigraphy of Denmark with their fragmented record of deposits remain ambiguous. Here we describe a newly found interglacial clay deposit from Ejby on Sjælland, Denmark, from a borehole at 55.695°N, 11.839°E (terrain elevation 5.7 m above sea level). We place the new occurrence on record and provide details of the macrofossil analysis of the sample. The clay contains remains of the present-day temperate bivalve Corbicula fluminalis and the caddis fly Hydropsyche contubernalis – both inhabiting rivers. The presence of C. fluminalis indicates that the deposit most probably is of Middle Pleistocene age, older than the last interglacial, the Eemian.","PeriodicalId":48475,"journal":{"name":"Geus Bulletin","volume":" ","pages":""},"PeriodicalIF":1.7,"publicationDate":"2022-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42245958","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study explores the application of long short-term memory (LSTM) networks to simulate runoff at the national scale of Denmark using data from 301 catchments. This is the first LSTM application on Danish data. The results were benchmarked against the Danish national water resources model (DK-model), a physically based hydrological model. The median Kling-Gupta Efficiency (KGE), a common metric to assess performance of runoff predictions (optimum of 1), increased from 0.7 (DK-model) to 0.8 (LSTM) when trained against all catchments. Overall, the LSTM outperformed the DK-model in 80% of catchments. Despite the compelling KGE evaluation, the water balance closure was modelled less accurately by the LSTM. The applicability of LSTM networks for modelling ungauged catchments was assessed via a spatial split-sample experiment. A 20% spatial hold-out showed poorer performance of the LSTM with respect to the DK model. However, after pre-training, that is, weight initialisation obtained from training against simulated data from the DK-model, the performance of the LSTM was effectively improved. This formed a convincing argument supporting the knowledge-guided machine learning (ML) paradigm to integrate physically based models and ML to train robust models that generalise well.
{"title":"Long short-term memory networks enhance rainfall-runoff modelling at the national scale of Denmark","authors":"J. Koch, R. Schneider","doi":"10.34194/geusb.v49.8292","DOIUrl":"https://doi.org/10.34194/geusb.v49.8292","url":null,"abstract":"This study explores the application of long short-term memory (LSTM) networks to simulate runoff at the national scale of Denmark using data from 301 catchments. This is the first LSTM application on Danish data. The results were benchmarked against the Danish national water resources model (DK-model), a physically based hydrological model. The median Kling-Gupta Efficiency (KGE), a common metric to assess performance of runoff predictions (optimum of 1), increased from 0.7 (DK-model) to 0.8 (LSTM) when trained against all catchments. Overall, the LSTM outperformed the DK-model in 80% of catchments. Despite the compelling KGE evaluation, the water balance closure was modelled less accurately by the LSTM. The applicability of LSTM networks for modelling ungauged catchments was assessed via a spatial split-sample experiment. A 20% spatial hold-out showed poorer performance of the LSTM with respect to the DK model. However, after pre-training, that is, weight initialisation obtained from training against simulated data from the DK-model, the performance of the LSTM was effectively improved. This formed a convincing argument supporting the knowledge-guided machine learning (ML) paradigm to integrate physically based models and ML to train robust models that generalise well.","PeriodicalId":48475,"journal":{"name":"Geus Bulletin","volume":" ","pages":""},"PeriodicalIF":1.7,"publicationDate":"2022-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47375226","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Glaciodynamic sequence stratigraphy provides a practical model for grouping and classifying complex geological data to aid interpretation of past climatic and environmental development in Quaternary successions. The principles of glaciodynamic sequence stratigraphy are applied here to summarise the complex glacial geological framework of Hvideklint on the island of Møn, south-east Denmark. The framework of the superimposed deformed Hvideklint is presented in a reconstructed geological cross-section of Hvideklint. For the construction of the architecture of the glaciotectonic complex, the interpretation of structures below sea level was based on a detailed new survey of the cliff section combined with construction of successive approximation balanced cross-sections. The new description is supported by drill hole data from the Jupiter database. Where chalk is not glaciotectonically deformed, the constructed depth to the top-chalk-surface is generally located about 30 m below sea level. In Hvideklint, thrust sheets with chalk are exposed 20 m above sea level, and the balanced cross-section constructions indicate that the décollement surface for a Hvideklint glaciotectonic complex is located about 80 m below sea level. Between the décollement level and the top of the complex, two or more thrust-fault flat-levels and connecting ramps add to the complex architecture of Hvideklint.
{"title":"The geological framework for Hvideklint, south-east Denmark, using glaciodynamic sequence stratigraphy","authors":"S. Pedersen, P. Gravesen","doi":"10.34194/geusb.v47.8304","DOIUrl":"https://doi.org/10.34194/geusb.v47.8304","url":null,"abstract":"Glaciodynamic sequence stratigraphy provides a practical model for grouping and classifying complex geological data to aid interpretation of past climatic and environmental development in Quaternary successions. The principles of glaciodynamic sequence stratigraphy are applied here to summarise the complex glacial geological framework of Hvideklint on the island of Møn, south-east Denmark. The framework of the superimposed deformed Hvideklint is presented in a reconstructed geological cross-section of Hvideklint. For the construction of the architecture of the glaciotectonic complex, the interpretation of structures below sea level was based on a detailed new survey of the cliff section combined with construction of successive approximation balanced cross-sections. The new description is supported by drill hole data from the Jupiter database. Where chalk is not glaciotectonically deformed, the constructed depth to the top-chalk-surface is generally located about 30 m below sea level. In Hvideklint, thrust sheets with chalk are exposed 20 m above sea level, and the balanced cross-section constructions indicate that the décollement surface for a Hvideklint glaciotectonic complex is located about 80 m below sea level. Between the décollement level and the top of the complex, two or more thrust-fault flat-levels and connecting ramps add to the complex architecture of Hvideklint.","PeriodicalId":48475,"journal":{"name":"Geus Bulletin","volume":" ","pages":""},"PeriodicalIF":1.7,"publicationDate":"2021-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45804941","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Det geologiske kortblad Møn omfatter Møn med de tilgrænsende øer Langø, Lindholm og Nyord samt mindre dele af Sjælland og Falster. Kortet består af dele af de topografiske kortblade 1511 I og 1512 II samt 1511 IV med randområder af tilgrænsende kortblade mod vest og nord. Møn opdeles i tre geomorfologiske områder: det stærkt kuperede Høje Møn mod øst, det småbakkede landskab omkring Stege Nor mod vest, og det flade marine forland omkring Nyord og Ulfshale. Høje Møn opbygges af opskudte skiver af skrivekridt og kvartære aflejringer, som det ses i Møns Klint. Skiverne er op til 80 m tykke, hvoraf skrivekridtet udgør ca. 50 m. Under hele Møn består prækvartæroverfladen af Maastrichtien skrivekridt i en dybde omkring kote –25 til –40 m. Mindre skiver af glacialtektonisk forstyrret skrivekridt optræder også omkring Stege Nor og langs sydkysten af det vestlige Møn ved Hvideklint. De ældste kvartære aflejringer er moræneler fra Saale-istiden og sand og ler fra Eem-mellemistiden. Derefter følger fluviale aflejringer og nedskylslag fra Tidlig Weichsel. Disse lag efterfølges af moræneler fra Ristinge Klint Till Formationen med over- og underliggende smeltevandsaflejringer fra Mellem Weichsel dannet under Ristinge Isfremstødet for ca. 55 000–50 000 år siden. Den næste enhed er Kraneled Formationen (ny formation), som efterfølges af moræneler tilhørende Klintholm Till Formationen (justeret formation) fra Klintholm Isfremstødet for 35 000–32 000 år siden. Formationen overlejres af mere end 10 m tykke enheder af gråt til olivengråt issøler med dropsten, smeltevandssand og lamineret fint sand samt diamikte aflejringer i Kobbelgård Formationen (ny formation). Denne formation blev aflejret i en issø, som dækkede store dele af Østersøen i en mildningsperiode for 32 000– 28 000 år siden. Denne enhed overlejres af eller er øverst sammenflettet med sand og grus tilhørende Stubberup Have Formationen (ny formation). Moræneler tilhørende den Midtdanske Till Formation blev aflejret under NØ-Isfremstødet for 23 000–20 000 år siden. Efter at NØ-Isen var smeltet tilbage fra østersøområdet, rykkede den Ungbaltiske Is frem fra den østlige del af Østersøen, hvorunder bl.a. Møns Klint og Hvideklint blev deformeret. En tilhørende strukturel enhed, Møns Klint Glacialdynamiske Kompleks, er defineret med fire sekvenser. Hele Hjelm Bugt dannede en glacial lobe, og nord herfor dannedes et randmorænestrøg. Radialt ud fra loben dannede smeltevandet store afløbskanaler fra gletsjerporte i den Ungbaltiske Is. Aflejring af sand og grus tilhørende Ny Borre Formationen (ny formation) skete i dette tidsrum. Under det Ungbaltiske Isfremstød blev Lolland Till Formationen aflejret som et relativt tyndt lag af moræneler. Ved slutningen af Weichsel-istiden for ca. 17 000 år siden smeltede den Ungbaltiske Is tilbage. Et residualt isdække i området nordøst for Møn sendte et genfremstød til det østlige Møn, som medførte en reorientering af skrivekridtskiverne i Møns Klint. I Sen Weichsel (17 000–11
{"title":"Kortbladsbeskrivelse, Geologisk kort over Danmark, 1:50 000, Møn Dele af 1511 I, 1511 IV og 1512 II","authors":"S. Pedersen, P. Gravesen","doi":"10.34194/geusb.v48.8293","DOIUrl":"https://doi.org/10.34194/geusb.v48.8293","url":null,"abstract":"Det geologiske kortblad Møn omfatter Møn med de tilgrænsende øer Langø, Lindholm og Nyord samt mindre dele af Sjælland og Falster. Kortet består af dele af de topografiske kortblade 1511 I og 1512 II samt 1511 IV med randområder af tilgrænsende kortblade mod vest og nord.\u0000Møn opdeles i tre geomorfologiske områder: det stærkt kuperede Høje Møn mod øst, det småbakkede landskab omkring Stege Nor mod vest, og det flade marine forland omkring Nyord og Ulfshale. Høje Møn opbygges af opskudte skiver af skrivekridt og kvartære aflejringer, som det ses i Møns Klint. Skiverne er op til 80 m tykke, hvoraf skrivekridtet udgør ca. 50 m. Under hele Møn består prækvartæroverfladen af Maastrichtien skrivekridt i en dybde omkring kote –25 til –40 m. Mindre skiver af glacialtektonisk forstyrret skrivekridt optræder også omkring Stege Nor og langs sydkysten af det vestlige Møn ved Hvideklint.\u0000De ældste kvartære aflejringer er moræneler fra Saale-istiden og sand og ler fra Eem-mellemistiden. Derefter følger fluviale aflejringer og nedskylslag fra Tidlig Weichsel. Disse lag efterfølges af moræneler fra Ristinge Klint Till Formationen med over- og underliggende smeltevandsaflejringer fra Mellem Weichsel dannet under Ristinge Isfremstødet for ca. 55 000–50 000 år siden. Den næste enhed er Kraneled Formationen (ny formation), som efterfølges af moræneler tilhørende Klintholm Till Formationen (justeret formation) fra Klintholm Isfremstødet for 35 000–32 000 år siden. Formationen overlejres af mere end 10 m tykke enheder af gråt til olivengråt issøler med dropsten, smeltevandssand og lamineret fint sand samt diamikte aflejringer i Kobbelgård Formationen (ny formation). Denne formation blev aflejret i en issø, som dækkede store dele af Østersøen i en mildningsperiode for 32 000– 28 000 år siden. Denne enhed overlejres af eller er øverst sammenflettet med sand og grus tilhørende Stubberup Have Formationen (ny formation). Moræneler tilhørende den Midtdanske Till Formation blev aflejret under NØ-Isfremstødet for 23 000–20 000 år siden. Efter at NØ-Isen var smeltet tilbage fra østersøområdet, rykkede den Ungbaltiske Is frem fra den østlige del af Østersøen, hvorunder bl.a. Møns Klint og Hvideklint blev deformeret. En tilhørende strukturel enhed, Møns Klint Glacialdynamiske Kompleks, er defineret med fire sekvenser. Hele Hjelm Bugt dannede en glacial lobe, og nord herfor dannedes et randmorænestrøg. Radialt ud fra loben dannede smeltevandet store afløbskanaler fra gletsjerporte i den Ungbaltiske Is. Aflejring af sand og grus tilhørende Ny Borre Formationen (ny formation) skete i dette tidsrum. Under det Ungbaltiske Isfremstød blev Lolland Till Formationen aflejret som et relativt tyndt lag af moræneler.\u0000Ved slutningen af Weichsel-istiden for ca. 17 000 år siden smeltede den Ungbaltiske Is tilbage. Et residualt isdække i området nordøst for Møn sendte et genfremstød til det østlige Møn, som medførte en reorientering af skrivekridtskiverne i Møns Klint. I Sen Weichsel (17 000–11 ","PeriodicalId":48475,"journal":{"name":"Geus Bulletin","volume":" ","pages":""},"PeriodicalIF":1.7,"publicationDate":"2021-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49248318","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. Japsen, P. Green, J. Bonow, M. Bjerager, J. Hopper
The geology of North-East Greenland (70–78°N) exposes unique evidence of the basin development between the Devonian collapse of the Caledonian Orogen and the extrusion of volcanics at the Paleocene–Eocene transition during break-up of the North-East Atlantic. Here we pay special attention to unconformities in the stratigraphic record – do they represent periods of stability and non-deposition or periods of subsidence and accumulation of rocks followed by episodes of uplift and erosion? To answer that and other questions, we used apatite fission-track analysis and vitrinite reflectance data together with stratigraphic landscape analysis and observations from the stratigraphic record to study the thermo-tectonic history of North-East Greenland. Our analysis reveals eight regional stages of post-Caledonian development: (1) Late Carboniferous uplift and erosion led to formation of a sub-Permian peneplain covered by coarse siliciclastic deposits. (2) Middle Triassic exhumation led to removal of a thick cover including a considerable thickness of upper Carboniferous – Middle Triassic rocks and produced thick siliciclastic deposits in the rift system. (3) Denudation at the transition between the Early and Middle Jurassic affected most of the study area outside the Jameson Land Basin and produced a weathered surface above which Middle–Upper Jurassic sediments accumulated. (4) Earliest Cretaceous uplift and erosion along the rifted margin and further inland accompanied the Mesozoic rift climax and produced coarse-grained sedimentary infill of the rift basins. (5) Mid-Cretaceous uplift and erosion initiated removal of Cretaceous post-rift sediments that had accumulated above the Mesozoic rifts and their hinterland, leading to cooling of Mesozoic sediments from maximum palaeotemperatures. (6) End-Eocene uplift was accompanied by faulting and intrusion of magmatic bodies and resulted in extensive mass wasting on the East Greenland shelf. This event initiated the removal of a thick post-rift succession that had accumulated after break-up and produced a peneplain near sea level, the Upper Planation Surface. (7) Late Miocene uplift and erosion, evidenced by massive progradation on the shelf, resulted in the formation of the Lower Planation Surface by incision below the uplifted Upper Planation Surface. (8) Early Pliocene uplift raised the Upper and the Lower Planation Surfaces to their present elevations of about 2 and 1 km above sea level, respectively, and initiated the formation of the present-day landscape through fluvial and glacial erosion. Additional cooling episodes of more local extent, related to igneous activity in the early Eocene and in the early Miocene, primarily affected parts of northern Jameson Land. The three earliest episodes had a profound impact beyond Greenland and accompanied the fragmentation of Pangaea. Younger episodes were controlled by plate-tectonic processes, possibly including dynamic support from the Iceland Plume. Our results e
{"title":"Episodic burial and exhumation in North-East Greenland before and after opening of the North-East Atlantic","authors":"P. Japsen, P. Green, J. Bonow, M. Bjerager, J. Hopper","doi":"10.34194/geusb.v45.5299","DOIUrl":"https://doi.org/10.34194/geusb.v45.5299","url":null,"abstract":"The geology of North-East Greenland (70–78°N) exposes unique evidence of the basin development between the Devonian collapse of the Caledonian Orogen and the extrusion of volcanics at the Paleocene–Eocene transition during break-up of the North-East Atlantic. Here we pay special attention to unconformities in the stratigraphic record – do they represent periods of stability and non-deposition or periods of subsidence and accumulation of rocks followed by episodes of uplift and erosion? To answer that and other questions, we used apatite fission-track analysis and vitrinite reflectance data together with stratigraphic landscape analysis and observations from the stratigraphic record to study the thermo-tectonic history of North-East Greenland. Our analysis reveals eight regional stages of post-Caledonian development: (1) Late Carboniferous uplift and erosion led to formation of a sub-Permian peneplain covered by coarse siliciclastic deposits. (2) Middle Triassic exhumation led to removal of a thick cover including a considerable thickness of upper Carboniferous – Middle Triassic rocks and produced thick siliciclastic deposits in the rift system. (3) Denudation at the transition between the Early and Middle Jurassic affected most of the study area outside the Jameson Land Basin and produced a weathered surface above which Middle–Upper Jurassic sediments accumulated. (4) Earliest Cretaceous uplift and erosion along the rifted margin and further inland accompanied the Mesozoic rift climax and produced coarse-grained sedimentary infill of the rift basins. (5) Mid-Cretaceous uplift and erosion initiated removal of Cretaceous post-rift sediments that had accumulated above the Mesozoic rifts and their hinterland, leading to cooling of Mesozoic sediments from maximum palaeotemperatures. (6) End-Eocene uplift was accompanied by faulting and intrusion of magmatic bodies and resulted in extensive mass wasting on the East Greenland shelf. This event initiated the removal of a thick post-rift succession that had accumulated after break-up and produced a peneplain near sea level, the Upper Planation Surface. (7) Late Miocene uplift and erosion, evidenced by massive progradation on the shelf, resulted in the formation of the Lower Planation Surface by incision below the uplifted Upper Planation Surface. (8) Early Pliocene uplift raised the Upper and the Lower Planation Surfaces to their present elevations of about 2 and 1 km above sea level, respectively, and initiated the formation of the present-day landscape through fluvial and glacial erosion. Additional cooling episodes of more local extent, related to igneous activity in the early Eocene and in the early Miocene, primarily affected parts of northern Jameson Land. The three earliest episodes had a profound impact beyond Greenland and accompanied the fragmentation of Pangaea. Younger episodes were controlled by plate-tectonic processes, possibly including dynamic support from the Iceland Plume. Our results e","PeriodicalId":48475,"journal":{"name":"Geus Bulletin","volume":"1 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2021-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43763181","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
O. Bennike, K. Andresen, P. Astrup, J. Olsen, M. Seidenkrantz
We propose a new relative shore-level curve for the Aarhus Bugt area, an embayment in eastern Jylland, Denmark, based on a compilation of published and new radiocarbon ages of organic material. Lakes existed in the area during the Late Glacial and Early Holocene. Lake level rose gradually until the region was inundated by the sea at c. 9000 cal. years BP. The relative sea level reached a high stand at about 6000 cal. years BP, when the local relative sea level was c. 3 m above present-day mean sea level. The Aarhus Bugt area was inundated by the sea later than the Limfjord area in northern Jylland, but earlier than the Lillebælt region in southern Denmark. The shore-level curves for these areas differ partly because the glacio-isostatic uplift was more pronounced in the Limfjord area than farther south and partly because the northern regions were inundated by the sea earlier than the southern areas.
{"title":"Late Glacial and Holocene shore-level changes in the Aarhus Bugt area, Denmark","authors":"O. Bennike, K. Andresen, P. Astrup, J. Olsen, M. Seidenkrantz","doi":"10.34194/geusb.v47.6530","DOIUrl":"https://doi.org/10.34194/geusb.v47.6530","url":null,"abstract":"We propose a new relative shore-level curve for the Aarhus Bugt area, an embayment in eastern Jylland, Denmark, based on a compilation of published and new radiocarbon ages of organic material. Lakes existed in the area during the Late Glacial and Early Holocene. Lake level rose gradually until the region was inundated by the sea at c. 9000 cal. years BP. The relative sea level reached a high stand at about 6000 cal. years BP, when the local relative sea level was c. 3 m above present-day mean sea level. The Aarhus Bugt area was inundated by the sea later than the Limfjord area in northern Jylland, but earlier than the Lillebælt region in southern Denmark. The shore-level curves for these areas differ partly because the glacio-isostatic uplift was more pronounced in the Limfjord area than farther south and partly because the northern regions were inundated by the sea earlier than the southern areas.","PeriodicalId":48475,"journal":{"name":"Geus Bulletin","volume":" ","pages":""},"PeriodicalIF":1.7,"publicationDate":"2021-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46240319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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