Pub Date : 2019-10-11DOI: 10.37570/bgsd-2019-67-06
Morten Bjergager, P. Alsen, J. Hovikoski, S. Lindström, Anders Pilgaard, L. Stemmerik, J. Therkelsen
The Wandel Sea Basin in eastern North Greenland forms the northern continuation of the offshore Danmarkshavn Basin and the conjugate margin to the western Barents Shelf south of Spitsbergen. The Triassic succession of eastern North Greenland, up to 700 m thick, spans the Induan (Dienerian) – Norian. The Triassic sediments rest unconformably on Upper Carboniferous and Upper Permian sediments, and are unconformably overlain by Upper Jurassic – Lower Cretaceous deposits. Based on recent fieldwork in the Wandel Sea Basin, five new and revised Triassic formations are described and included in the Trolle Land Group (revised). The Lower Triassic (Induan) Parish Bjerg Formation (revised) consists of marine sandstones, fluvial conglomerates and sandstones, and muddy flood-plain deposits. It is conformably overlain by Lower Triassic (Dienerian – lower Spathian) offshore mudstones with minor sand-dominated intervals of the Ugleungernes Dal Formation (new). The upper Spathian to Ladinian Dunken Formation (revised) is represented mainly by marine sandstones. A marked erosional unconformity characterises the base of the overlying Upper Triassic (Carnian – Norian) Storekløft Formation (new) composed of marginal marine to marine, massive sandstones and conglomerates as well as cross-bedded and biomottled marine sandstones and minor mudstone units. The Isrand Formation (mainly Middle Triassic) consists of laminated mudstones with minor thin sandstone units that were deposited in slope and basin floor settings in the eastern deeper part of the Wandel Sea Basin in Kronprins Christian Land. The Triassic succession of the Wandel Sea Basin represents a well-constrained shallow shelf to deep shelf / basin floor transect and thus forms an excellent outcrop analogue to the time-equivalent intervals in the western Barents Sea basins and the Danmarkshavn Basin offshore North-East Greenland.
北格陵兰岛东部的Wandel海盆地形成了海上Danmarkshavn盆地的北部延伸，以及斯匹次卑尔根岛以南的西部巴伦支陆架的共轭边缘。北格陵兰岛东部的三叠纪演替，厚达700米，跨越了Induan (Dienerian) - Norian。三叠纪沉积物不整合位于上石炭统和上二叠统沉积物之上，并被上侏罗统-下白垩统沉积物不整合覆盖。根据最近在Wandel海盆地的野外工作，描述了5个新的和修订的三叠纪地层，并将其纳入了特罗勒陆群(修订)。下三叠统(Induan) Parish Bjerg组(订正)由海相砂岩、河流砾岩和砂岩以及泥质洪泛平原沉积组成。它被下三叠统(二叠统-下斯巴达统)近海泥岩整合覆盖，并具有较小的以砂为主的Ugleungernes Dal组(新)层段。上Spathian—Ladinian Dunken组(订正)以海相砂岩为主。上三叠统(卡尼期-诺里期)Storekløft组(新)的基底具有明显的侵蚀不整合特征，该组由边缘海相到海相块状砂岩和砾岩以及交错层状和生物侵蚀的海相砂岩和小型泥岩单元组成。岛组(主要为中三叠统)由层状泥岩和少量薄砂岩单元组成，沉积于Kronprins Christian Land Wandel海盆地东部较深的斜坡和盆地底环境中。Wandel海盆地的三叠纪演替代表了一个约束良好的浅陆架到深陆架/盆地底样带，因此形成了一个与西巴伦支海盆地和格陵兰东北部近海Danmarkshavn盆地的时间等效间隔非常相似的露头。
{"title":"Triassic lithostratigraphy of the Wandel Sea Basin, North Greenland","authors":"Morten Bjergager, P. Alsen, J. Hovikoski, S. Lindström, Anders Pilgaard, L. Stemmerik, J. Therkelsen","doi":"10.37570/bgsd-2019-67-06","DOIUrl":"https://doi.org/10.37570/bgsd-2019-67-06","url":null,"abstract":"The Wandel Sea Basin in eastern North Greenland forms the northern continuation of the offshore Danmarkshavn Basin and the conjugate margin to the western Barents Shelf south of Spitsbergen. The Triassic succession of eastern North Greenland, up to 700 m thick, spans the Induan (Dienerian) – Norian. The Triassic sediments rest unconformably on Upper Carboniferous and Upper Permian sediments, and are unconformably overlain by Upper Jurassic – Lower Cretaceous deposits. Based on recent fieldwork in the Wandel Sea Basin, five new and revised Triassic formations are described and included in the Trolle Land Group (revised). The Lower Triassic (Induan) Parish Bjerg Formation (revised) consists of marine sandstones, fluvial conglomerates and sandstones, and muddy flood-plain deposits. It is conformably overlain by Lower Triassic (Dienerian – lower Spathian) offshore mudstones with minor sand-dominated intervals of the Ugleungernes Dal Formation (new). The upper Spathian to Ladinian Dunken Formation (revised) is represented mainly by marine sandstones. A marked erosional unconformity characterises the base of the overlying Upper Triassic (Carnian – Norian) Storekløft Formation (new) composed of marginal marine to marine, massive sandstones and conglomerates as well as cross-bedded and biomottled marine sandstones and minor mudstone units. The Isrand Formation (mainly Middle Triassic) consists of laminated mudstones with minor thin sandstone units that were deposited in slope and basin floor settings in the eastern deeper part of the Wandel Sea Basin in Kronprins Christian Land. The Triassic succession of the Wandel Sea Basin represents a well-constrained shallow shelf to deep shelf / basin floor transect and thus forms an excellent outcrop analogue to the time-equivalent intervals in the western Barents Sea basins and the Danmarkshavn Basin offshore North-East Greenland.","PeriodicalId":55310,"journal":{"name":"Bulletin of the Geological Society of Denmark","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2019-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47552298","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}
Pub Date : 2019-05-20DOI: 10.37570/bgsd-2019-67-04
O. Bennike, N. Nørgaard‐Pedersen, J. Jensen, K. Andresen, M. Seidenkrantz
This paper presents new marine evidence of Lateglacial and Holocene environmental changes in the western part of Limfjorden, and provides a review of the geological history/development of this part of northern Jylland, Denmark. Lateglacial clay without fossils is widespread in the region and is probably a glaciolacustrine deposit. Limfjorden began to form as a strait in the Early Holocene due to rising relative sea level and the oldest marine shells are dated to c. 9300 cal. years BP. We propose a new relative sealevel curve for the region based on new and published data, which appear to confirm that the relative sea-level change was not extremely rapid, which was suggested earlier. During the Mid-Holocene a wide connection existed from the western part of Limfjorden to the North Sea in the west and more narrow connections existed between Limfjorden and Skagerrak in the north. The marine fauna included several species that indicate warmer and more salty waters than at present. Gradually, the connections to the North Sea and Skagerrak closed due to long-shore sediment transport and deposition of aeolian sand combined with a fall in the relative sea level during the Middle- to Late Holocene. During the Viking Age, 800–1050 CE (Common Era), the western connection to the North Sea was still open, but around 1200 CE it was closed by a coastal sandy barrier and the western part of Limfjorden became brackish. The coastal barrier was flooded on several occasions but soon formed again. After 1825 CE the western connection from Limfjorden to the North Sea has been maintained artificially.
{"title":"Development of the western Limfjord, Denmark, after the last deglaciation: a review with new data","authors":"O. Bennike, N. Nørgaard‐Pedersen, J. Jensen, K. Andresen, M. Seidenkrantz","doi":"10.37570/bgsd-2019-67-04","DOIUrl":"https://doi.org/10.37570/bgsd-2019-67-04","url":null,"abstract":"This paper presents new marine evidence of Lateglacial and Holocene environmental changes in the western part of Limfjorden, and provides a review of the geological history/development of this part of northern Jylland, Denmark. Lateglacial clay without fossils is widespread in the region and is probably a glaciolacustrine deposit. Limfjorden began to form as a strait in the Early Holocene due to rising relative sea level and the oldest marine shells are dated to c. 9300 cal. years BP. We propose a new relative sealevel curve for the region based on new and published data, which appear to confirm that the relative sea-level change was not extremely rapid, which was suggested earlier. During the Mid-Holocene a wide connection existed from the western part of Limfjorden to the North Sea in the west and more narrow connections existed between Limfjorden and Skagerrak in the north. The marine fauna included several species that indicate warmer and more salty waters than at present. Gradually, the connections to the North Sea and Skagerrak closed due to long-shore sediment transport and deposition of aeolian sand combined with a fall in the relative sea level during the Middle- to Late Holocene. During the Viking Age, 800–1050 CE (Common Era), the western connection to the North Sea was still open, but around 1200 CE it was closed by a coastal sandy barrier and the western part of Limfjorden became brackish. The coastal barrier was flooded on several occasions but soon formed again. After 1825 CE the western connection from Limfjorden to the North Sea has been maintained artificially.","PeriodicalId":55310,"journal":{"name":"Bulletin of the Geological Society of Denmark","volume":"1 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2019-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42856977","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}
Pub Date : 2018-11-22DOI: 10.37570/bgsd-2018-66-14
O. Malchyk, M. Machalski
The atypical Late Cretaceous nautilid Epicymatoceras vaelsense (Binkhorst van den Binkhorst, 1862) is described and illustrated on the basis of three specimens from the Maastrichtian white chalk of Denmark. One of these is probably from the lower/upper Maastrichtian boundary interval at Frejlev, while the other two originate from the uppermost Maastrichtian chalk as exposed in the Dania quarry; both localities are in Jylland, northern Denmark. These are first reports of E. vaelsense from Denmark; the species has previously been recorded from the uppermost Campanian and lower Maastrichtian of the Netherlands, Belgium, northern Germany and Poland. The presence of E. vaelsense in the topmost Maastrichtian white chalk in the Dania quarry is considered the youngest record of Epicymatoceras known to date, suggesting the persistence of the genus until the end of the Cretaceous. The diameter of the embryonic conch of the Danish E. vaelsense may be estimated at c. 30 mm, based on an individual from the Dania quarry, confirming earlier observations that the species possessed one of the largest embryonic conchs amongst Late Cretaceous nautilids.
非典型的晚白垩世鹦鹉螺Epicymatoceras vaelsense（Binkhorst-van den Binkhorst，1862）是在丹麦马斯特里赫特白白垩系的三个标本的基础上描述和说明的。其中一个可能来自Frejlev的马斯特里赫特阶下/上边界层段，而另外两个可能来自Dania采石场暴露的马斯特里奇特阶最上层白垩；这两个地方都在丹麦北部的吉兰。这些是来自丹麦的E.vaelsense的首次报告；该物种以前曾在荷兰、比利时、德国北部和波兰的坎帕尼亚阶最上层和马斯特里赫特阶下统有记录。在达尼亚采石场马斯特里赫特阶最顶端的白色白垩中发现了E.vaelsense，这被认为是迄今为止已知的最年轻的Epicymatoceras记录，表明该属一直存在到白垩纪末。丹麦E.vaelsense的胚胎海螺的直径估计为c。30毫米，基于达尼亚采石场的一个个体，证实了早期的观察结果，即该物种拥有晚白垩世鹦鹉螺中最大的胚胎海螺之一。
{"title":"First record of Epicymatoceras vaelsense (Nautilida) from the Maastrichtian white chalk of northern Denmark","authors":"O. Malchyk, M. Machalski","doi":"10.37570/bgsd-2018-66-14","DOIUrl":"https://doi.org/10.37570/bgsd-2018-66-14","url":null,"abstract":"The atypical Late Cretaceous nautilid Epicymatoceras vaelsense (Binkhorst van den Binkhorst, 1862) is described and illustrated on the basis of three specimens from the Maastrichtian white chalk of Denmark. One of these is probably from the lower/upper Maastrichtian boundary interval at Frejlev, while the other two originate from the uppermost Maastrichtian chalk as exposed in the Dania quarry; both localities are in Jylland, northern Denmark. These are first reports of E. vaelsense from Denmark; the species has previously been recorded from the uppermost Campanian and lower Maastrichtian of the Netherlands, Belgium, northern Germany and Poland. The presence of E. vaelsense in the topmost Maastrichtian white chalk in the Dania quarry is considered the youngest record of Epicymatoceras known to date, suggesting the persistence of the genus until the end of the Cretaceous. The diameter of the embryonic conch of the Danish E. vaelsense may be estimated at c. 30 mm, based on an individual from the Dania quarry, confirming earlier observations that the species possessed one of the largest embryonic conchs amongst Late Cretaceous nautilids.","PeriodicalId":55310,"journal":{"name":"Bulletin of the Geological Society of Denmark","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2018-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43903451","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}
Pub Date : 2018-11-06DOI: 10.37570/bgsd-2018-66-13
Thomas Weidner, J. R. Ebbestad
Centropleurid trilobites include five genera of which Centropleura Angelin, Anopolenus Salter, Clarella Howell and Luhops Šnajdr are known from eight species in the traditional middle Cambrian (Miaolingian Series, Drumian Stage) of Sweden and Denmark (Bornholm). Beishanella Xiang & Zhang has not been recorded in Scandinavia so far, and no centropleurids have been reported from Norway. Of these taxa, only Centropleura is common in Scandinavia. Two pygidia previously identified as Centropleura sp. and Anopolenus sp. from erratics in Germany and Bornholm, respectively, as well as a new pygidum from Scania in Sweden are here identified as Anopolenus henrici Salter. Elsewhere, the species is known from Wales, Avalonian Canada, Siberia, Alaska, and Sardinia, occurring in the A. atavus and P. punctuosus zones (the former in Siberia only). The presence of this species increases the known diversity of Centropleuridae in Scandinavia and is important for correlation between Baltica and Avalonia.
中心虫三叶虫包括五个属，其中瑞典和丹麦传统中寒武纪（苗林系，德拉米阶）的八个种中已知中心虫Angelin属、Anopolenus Salter属、Clarella Howell属和LuhopsŠnajdr属。到目前为止，在斯堪的纳维亚半岛还没有记录到Xiang和Zhang的Beishanella，在挪威也没有记录到中心体。在这些分类群中，只有中翅目在斯堪的纳维亚很常见。先前分别来自德国和博恩霍尔姆的两种pygidia被鉴定为Centropleura sp.和Anopolenus sp.，以及来自瑞典斯堪尼亚的一种新的pygidia在这里被鉴定为Anopolens henrici Salter。在其他地方，该物种分布在威尔士、加拿大阿瓦隆、西伯利亚、阿拉斯加和撒丁岛，分布在A.atavus和P.punctusus带（前者仅在西伯利亚）。该物种的存在增加了斯堪的纳维亚地区已知的Centreleuridae的多样性，对Baltica和Avalonia之间的相关性很重要。
{"title":"Anopolenus henrici Salter, a middle Cambrian (Drumian) centropleurid trilobite from the Alum Shale Formation of Scandinavia","authors":"Thomas Weidner, J. R. Ebbestad","doi":"10.37570/bgsd-2018-66-13","DOIUrl":"https://doi.org/10.37570/bgsd-2018-66-13","url":null,"abstract":"Centropleurid trilobites include five genera of which Centropleura Angelin, Anopolenus Salter, Clarella Howell and Luhops Šnajdr are known from eight species in the traditional middle Cambrian (Miaolingian Series, Drumian Stage) of Sweden and Denmark (Bornholm). Beishanella Xiang & Zhang has not been recorded in Scandinavia so far, and no centropleurids have been reported from Norway. Of these taxa, only Centropleura is common in Scandinavia. Two pygidia previously identified as Centropleura sp. and Anopolenus sp. from erratics in Germany and Bornholm, respectively, as well as a new pygidum from Scania in Sweden are here identified as Anopolenus henrici Salter. Elsewhere, the species is known from Wales, Avalonian Canada, Siberia, Alaska, and Sardinia, occurring in the A. atavus and P. punctuosus zones (the former in Siberia only). The presence of this species increases the known diversity of Centropleuridae in Scandinavia and is important for correlation between Baltica and Avalonia.","PeriodicalId":55310,"journal":{"name":"Bulletin of the Geological Society of Denmark","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2018-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46465722","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}
Pub Date : 2018-10-26DOI: 10.37570/bgsd-2018-66-12
O. Bennike
{"title":"Book Review: Fischer, A. & Pedersen, L. (eds) 2018: Oceans of Archaeology.","authors":"O. Bennike","doi":"10.37570/bgsd-2018-66-12","DOIUrl":"https://doi.org/10.37570/bgsd-2018-66-12","url":null,"abstract":"","PeriodicalId":55310,"journal":{"name":"Bulletin of the Geological Society of Denmark","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2018-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49245005","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}
Pub Date : 2018-10-04DOI: 10.37570/bgsd-2018-66-11
Kristine Steigardotter Myrvold, J. Milán, J. A. Rasmussen
Two new fragments of a turtle carapace and a turtle plastron (hypoplastron) have been recovered from glacially transported boulders of Danian and Selandian age. The hypoplastron is identified as Ctenochelys cf. stenoporus, while the carapace fragment can only be assigned to the family Cheloniidae indet. Both specimens show evidence of predation by crocodilians in the form of rows of circular pits in the bones, and one specimen has rows of elongated scrape traces interpreted as scavenging by sharks. Together with the other, rare finds from the middle Danian of the Faxe Quarry and from late Danian deposits in the Copenhagen area, these new finds add important new knowledge to the sparse fossil record of turtles in Scandinavia, as well as evidence that the genus Ctenochelys survived across the K/Pg Boundary.
{"title":"Two new finds of turtle remains from the Danian and Selandian (Paleocene) deposits of Denmark with evidence of predation by crocodilians and sharks","authors":"Kristine Steigardotter Myrvold, J. Milán, J. A. Rasmussen","doi":"10.37570/bgsd-2018-66-11","DOIUrl":"https://doi.org/10.37570/bgsd-2018-66-11","url":null,"abstract":"Two new fragments of a turtle carapace and a turtle plastron (hypoplastron) have been recovered from glacially transported boulders of Danian and Selandian age. The hypoplastron is identified as Ctenochelys cf. stenoporus, while the carapace fragment can only be assigned to the family Cheloniidae indet. Both specimens show evidence of predation by crocodilians in the form of rows of circular pits in the bones, and one specimen has rows of elongated scrape traces interpreted as scavenging by sharks. Together with the other, rare finds from the middle Danian of the Faxe Quarry and from late Danian deposits in the Copenhagen area, these new finds add important new knowledge to the sparse fossil record of turtles in Scandinavia, as well as evidence that the genus Ctenochelys survived across the K/Pg Boundary.","PeriodicalId":55310,"journal":{"name":"Bulletin of the Geological Society of Denmark","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2018-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42352683","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}
Pub Date : 2018-09-26DOI: 10.37570/bgsd-2018-66-10
A. C. Glad, M. E. Willumsen, L. O. Boldreel, L. Clemmensen
Fluvial deposits are amongst the most important terrestrial hydrocarbon reservoirs, but the complex nature of these deposits is challenging in subsurface reservoir characterisation. This study is the first detailed facies analysis of the meandering river deposits of the Middle Jurassic Alma Field situated in the southern Danish North Sea. The fluvial sandstones and their associated deposits are described and interpreted based on studies from two core sites (Alma-1X and Alma-2X). The facies analysis of the cores demonstrates the presence of three meandering river facies associations: Channel deposits, channel margin deposits and floodplain deposits. The channel deposits comprise channel thalweg and point bar sediments, the channel margin deposits include crevasse channel and crevasse splay sediments, while the floodplain deposits comprise overbank and backswamp sediments. The point bar deposits are composed of fine- to medium-grained sandstones but can contain intervals of finer grained sediments, particularly in their upper parts where they can grade into muddy sandstones or true heterolithic deposits. Preserved sand body thicknesses (channel thalweg and point bar deposits) in both Alma cores have a mean value of 2.6 m and a maximum value of 4.35 m (Alma-1X) and 6.55 m (Alma-2X). Using maximum values of channel deposit thicknesses, and assuming the preservation conditions are met, the width of the largest ancient channel belt in Alma-1X would be between 90 m and 200 m or around 900 m, depending on whether the fluvial system is mud-rich or sand-rich. The same method applied to Alma-2X gives a width of the largest channel belt between 130 m and 330 m or around 1300 m. Fluvial sediments of the Middle Jurassic Scalby Formation (north-east England) were deposited in a sandy meandering river with sedimentary characteristics corresponding to those observed in the Alma cores. Outcrop analogue investigations of this formation were carried out to examine the architecture of the fluvial facies in a two-dimensional section with emphasis on channel thalweg and point bar deposits. Combined evidence from core analysis and outcrop analogue studies suggests that the fluvial deposits in the Alma Field represent a mixed-load meandering river system with sandy point bars. The meandering river system developed on a coastal plain with overbank fines and organic-rich backswamp deposits. The mud-rich or heterolithic deposits in the upper part of the point bar facies intervals are noteworthy and could indicate markedly fluctuating discharge in a mixed-load river.
{"title":"Meandering river deposits in sediment cores, the Middle Jurassic Alma Field, Southern Danish Central Graben","authors":"A. C. Glad, M. E. Willumsen, L. O. Boldreel, L. Clemmensen","doi":"10.37570/bgsd-2018-66-10","DOIUrl":"https://doi.org/10.37570/bgsd-2018-66-10","url":null,"abstract":"Fluvial deposits are amongst the most important terrestrial hydrocarbon reservoirs, but the complex nature of these deposits is challenging in subsurface reservoir characterisation. This study is the first detailed facies analysis of the meandering river deposits of the Middle Jurassic Alma Field situated in the southern Danish North Sea. The fluvial sandstones and their associated deposits are described and interpreted based on studies from two core sites (Alma-1X and Alma-2X). The facies analysis of the cores demonstrates the presence of three meandering river facies associations: Channel deposits, channel margin deposits and floodplain deposits. The channel deposits comprise channel thalweg and point bar sediments, the channel margin deposits include crevasse channel and crevasse splay sediments, while the floodplain deposits comprise overbank and backswamp sediments. The point bar deposits are composed of fine- to medium-grained sandstones but can contain intervals of finer grained sediments, particularly in their upper parts where they can grade into muddy sandstones or true heterolithic deposits. Preserved sand body thicknesses (channel thalweg and point bar deposits) in both Alma cores have a mean value of 2.6 m and a maximum value of 4.35 m (Alma-1X) and 6.55 m (Alma-2X). Using maximum values of channel deposit thicknesses, and assuming the preservation conditions are met, the width of the largest ancient channel belt in Alma-1X would be between 90 m and 200 m or around 900 m, depending on whether the fluvial system is mud-rich or sand-rich. The same method applied to Alma-2X gives a width of the largest channel belt between 130 m and 330 m or around 1300 m.\u0000Fluvial sediments of the Middle Jurassic Scalby Formation (north-east England) were deposited in a sandy meandering river with sedimentary characteristics corresponding to those observed in the Alma cores. Outcrop analogue investigations of this formation were carried out to examine the architecture of the fluvial facies in a two-dimensional section with emphasis on channel thalweg and point bar deposits.\u0000Combined evidence from core analysis and outcrop analogue studies suggests that the fluvial deposits in the Alma Field represent a mixed-load meandering river system with sandy point bars. The meandering river system developed on a coastal plain with overbank fines and organic-rich backswamp deposits. The mud-rich or heterolithic deposits in the upper part of the point bar facies intervals are noteworthy and could indicate markedly fluctuating discharge in a mixed-load river.","PeriodicalId":55310,"journal":{"name":"Bulletin of the Geological Society of Denmark","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2018-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42053229","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}
Pub Date : 2018-09-10DOI: 10.37570/bgsd-2018-66-09
J. Milán, E. Rasmussen, K. Dybkjær
A large, well-preserved vertebrate coprolite found in the clay pit Sofienlund Lergrav, Jylland, is identified as crocodilian due to its size and morphology. The coprolite consists of several concentric layers wrapped around a more homogeneous core. Weak constriction marks are present on the surface. Dinoflagellate cyst contents of the coprolite indicate a mid-Lutetian to earliest Rupelian (middle Eocene to earliest Oligocene) age, which at Sofienlund Lergrav places it within the lower Oligocene Viborg Formation. The coprolite can thus be dated as approximately 33–34 Ma old. The Viborg Formation in Denmark represents a period with deposition of hemipelagic marine clay and formation of glaucony. The nearest shoreline was located c. 200 km north of the location of the present day Sofienlund Lergrav, and the climate was humid, warm-temperate to sub-tropical. The presence of a crocodilian coprolite is an important addition to the sparse Oligocene vertebrate fauna of Denmark, which previously only consisted of sharks and cetaceans.
{"title":"A crocodilian coprolite from the lower Oligocene Viborg Formation of Sofienlund Lergrav, Denmark","authors":"J. Milán, E. Rasmussen, K. Dybkjær","doi":"10.37570/bgsd-2018-66-09","DOIUrl":"https://doi.org/10.37570/bgsd-2018-66-09","url":null,"abstract":"A large, well-preserved vertebrate coprolite found in the clay pit Sofienlund Lergrav, Jylland, is identified as crocodilian due to its size and morphology. The coprolite consists of several concentric layers wrapped around a more homogeneous core. Weak constriction marks are present on the surface. Dinoflagellate cyst contents of the coprolite indicate a mid-Lutetian to earliest Rupelian (middle Eocene to earliest Oligocene) age, which at Sofienlund Lergrav places it within the lower Oligocene Viborg Formation. The coprolite can thus be dated as approximately 33–34 Ma old. The Viborg Formation in Denmark represents a period with deposition of hemipelagic marine clay and formation of glaucony.\u0000The nearest shoreline was located c. 200 km north of the location of the present day Sofienlund Lergrav, and the climate was humid, warm-temperate to sub-tropical. The presence of a crocodilian coprolite is an important addition to the sparse Oligocene vertebrate fauna of Denmark, which previously only consisted of sharks and cetaceans.","PeriodicalId":55310,"journal":{"name":"Bulletin of the Geological Society of Denmark","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2018-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47253045","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}
Pub Date : 2018-09-07DOI: 10.37570/bgsd-2018-66-08
P. Souza, A. Kroon, L. Nielsen
Detailed topographic data and high-resolution ground-penetrating radar (GPR) reflection data are presented from the present-day beach and across successive raised beach ridges at Itilleq, south-west Disko, West Greenland. In the western part of the study area, the present low-tide level is well defined by an abrupt change in sediment grain size between the sandy foreshore and the upper shoreface that is characterised by frequently occurring large clasts. The main parts of both fine and large clasts appear to be locally derived. Seaward-dipping reflections form downlap points, which are clearly identified in all beach-ridge GPR profiles. Most of them are located at the boundary between a unit with reflection characteristics representing palaeo-foreshore deposits and a deeper and more complex radar unit characterised by diffractions; the deeper unit is not penetrated to large depths by the GPR signals. Based on observations of the active shoreface regime, large clasts are interpreted to give rise to scattering observed near the top of the deeper radar unit. We regard the downlap points located at this radar boundary as markers of palaeo-low-tide levels. In some places, scattering hyperbolas are more pronounced and frequent than in others, suggesting differences in the occurrence of large boulders.
{"title":"Beach-ridge architecture constrained by beach topography and ground-penetrating radar, Itilleq (Laksebugt), south-west Disko, Greenland – implications for sea-level reconstructions.","authors":"P. Souza, A. Kroon, L. Nielsen","doi":"10.37570/bgsd-2018-66-08","DOIUrl":"https://doi.org/10.37570/bgsd-2018-66-08","url":null,"abstract":"Detailed topographic data and high-resolution ground-penetrating radar (GPR) reflection data are presented from the present-day beach and across successive raised beach ridges at Itilleq, south-west Disko, West Greenland. In the western part of the study area, the present low-tide level is well defined by an abrupt change in sediment grain size between the sandy foreshore and the upper shoreface that is characterised by frequently occurring large clasts. The main parts of both fine and large clasts appear to be locally derived. Seaward-dipping reflections form downlap points, which are clearly identified in all beach-ridge GPR profiles. Most of them are located at the boundary between a unit with reflection characteristics representing palaeo-foreshore deposits and a deeper and more complex radar unit characterised by diffractions; the deeper unit is not penetrated to large depths by the GPR signals. Based on observations of the active shoreface regime, large clasts are interpreted to give rise to scattering observed near the top of the deeper radar unit. We regard the downlap points located at this radar boundary as markers of palaeo-low-tide levels. In some places, scattering hyperbolas are more pronounced and frequent than in others, suggesting differences in the occurrence of large boulders.","PeriodicalId":55310,"journal":{"name":"Bulletin of the Geological Society of Denmark","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2018-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47774560","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}
Pub Date : 2018-08-31DOI: 10.37570/bgsd-2018-66-07
M. L. Hjuler, V. Hansen, I. Fabricius
Scanning and transmission electron microscopy (SEM and TEM) are capable of characterising the morphology and structure of sub-micron size substances attached to chalk particle surfaces. Some characteristics, however, may originate from sample preparation or reflect interaction between sample and the electron beam. Misinterpretation of surface features may lead to wrong conclusions regarding grain surface properties and cementation level and thus to erroneous characterisation of hydrocarbon reservoirs with respect to e.g. wettability, mechanical strength and maximum burial depth. In SEM, conductive coatings may mask surface details or generate artificial ornamentations, and carbon adhesive discs may cause the chalk surface to be covered with a thin carbon film. Electron beam acceleration voltage controls the degree of detail revealed by the electron beam, but in SEM a high electron beam acceleration voltage may provoke bending or curling of ultrathin particles. Recent organic filaments may be confused with clay flakes, and authigenic non-carbonate minerals may have formed in the pore fluid and settled during fluid removal. In TEM, the high acceleration voltage may cause beam damage to calcite and transform the outermost atomic layers into Ca oxide. Thin graphite membranes observed by TEM may be contamination from the carbon film supporting the sample, and overlapping chalk particles in samples formed by drying of a suspension may give the impression of being cemented together. In TEM residual adhesive from the ion-milling process can be confused with cementation features.
{"title":"Interpretational challenges related to studies of chalk particle surfaces in scanning and transmission electron microscopy","authors":"M. L. Hjuler, V. Hansen, I. Fabricius","doi":"10.37570/bgsd-2018-66-07","DOIUrl":"https://doi.org/10.37570/bgsd-2018-66-07","url":null,"abstract":"Scanning and transmission electron microscopy (SEM and TEM) are capable of characterising the morphology and structure of sub-micron size substances attached to chalk particle surfaces. Some characteristics, however, may originate from sample preparation or reflect interaction between sample and the electron beam. Misinterpretation of surface features may lead to wrong conclusions regarding grain surface properties and cementation level and thus to erroneous characterisation of hydrocarbon\u0000reservoirs with respect to e.g. wettability, mechanical strength and maximum burial depth. In SEM, conductive coatings may mask surface details or generate artificial ornamentations, and carbon adhesive discs may cause the chalk surface to be covered with a thin carbon film. Electron beam acceleration voltage controls the degree of detail revealed by the electron beam, but in SEM a high electron beam acceleration voltage may provoke bending or curling of ultrathin particles. Recent organic filaments\u0000may be confused with clay flakes, and authigenic non-carbonate minerals may have formed in the pore fluid and settled during fluid removal. In TEM, the high acceleration voltage may cause beam damage to calcite and transform the outermost atomic layers into Ca oxide. Thin graphite membranes observed by TEM may be contamination from the carbon film supporting the sample, and overlapping chalk particles in samples formed by drying of a suspension may give the impression of being cemented together. In TEM residual adhesive from the ion-milling process can be confused with cementation features.","PeriodicalId":55310,"journal":{"name":"Bulletin of the Geological Society of Denmark","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2018-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45051275","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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