Over the past thirty years, exploration of the terrestrial Mesozoic section in Utah has resulted in a more than fivefold increase in the known species of dinosaurs. A highly resolved temporal and sequence stratigraphic framework for these strata is facilitating the utility of these newly discovered dinosaur assemblages in geologic, evolutionary, paleoecologic, and paleogeographic research. Local subsidence due to salt tectonics in the northern Paradox Basin is responsible for this region of eastern Utah preserving basal Cretaceous dinosaur faunas, known nowhere else in North America, that document paleobiogeographic connections across the proto-North Atlantic with Europe. The more medial Cretaceous strata west of the San Rafael Swell, in central Utah, preserve a unique dinosaur assemblage on an isolated North America. These strata also record the first immigration of Asian dinosaurs into North America and the last occurrences of a number of endemic North American dinosaur lineages. Through the Late Cretaceous, extensive, fossiliferous floodplain deposits are exposed in the high plateaus of southern Utah within the Grand Canyon Bight on the western side of the Late Cretaceous Western Interior Seaway. Research on microvertebrate sites has resulted in a diverse record of vertebrate life substage by substage through most of the Upper Cretaceous sequence. Particularly, rich dinosaur-bearing beds through the Campanian have resulted in the discovery of many new dinosaur species distinct from the coeval dinosaur-bearing beds farther north along the western coast of the Western Interior Seaway in Montana and Alberta. The further development of these numerous rich dinosaur assemblages will provide the basis for considerable research in the future.
{"title":"Dinosaur biostratigraphy of the Nonmarine Cretaceous of Utah","authors":"J. Kirkland, J. Sertich, A. Titus","doi":"10.1144/sp545-2023-211","DOIUrl":"https://doi.org/10.1144/sp545-2023-211","url":null,"abstract":"\u0000 Over the past thirty years, exploration of the terrestrial Mesozoic section in Utah has resulted in a more than fivefold increase in the known species of dinosaurs. A highly resolved temporal and sequence stratigraphic framework for these strata is facilitating the utility of these newly discovered dinosaur assemblages in geologic, evolutionary, paleoecologic, and paleogeographic research. Local subsidence due to salt tectonics in the northern Paradox Basin is responsible for this region of eastern Utah preserving basal Cretaceous dinosaur faunas, known nowhere else in North America, that document paleobiogeographic connections across the proto-North Atlantic with Europe. The more medial Cretaceous strata west of the San Rafael Swell, in central Utah, preserve a unique dinosaur assemblage on an isolated North America. These strata also record the first immigration of Asian dinosaurs into North America and the last occurrences of a number of endemic North American dinosaur lineages. Through the Late Cretaceous, extensive, fossiliferous floodplain deposits are exposed in the high plateaus of southern Utah within the Grand Canyon Bight on the western side of the Late Cretaceous Western Interior Seaway. Research on microvertebrate sites has resulted in a diverse record of vertebrate life substage by substage through most of the Upper Cretaceous sequence. Particularly, rich dinosaur-bearing beds through the Campanian have resulted in the discovery of many new dinosaur species distinct from the coeval dinosaur-bearing beds farther north along the western coast of the Western Interior Seaway in Montana and Alberta. The further development of these numerous rich dinosaur assemblages will provide the basis for considerable research in the future.","PeriodicalId":281618,"journal":{"name":"Geological Society, London, Special Publications","volume":"31 S106","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140224616","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Products of geological processes such as rock formations, unconformities, structures, minerals, fossils, and landforms, represent unique records of the evolution of the Earth. These form a coherent picture showing how the Earth evolved. The picture becomes blurred with antiquity. Consequently, there are challenges in gathering information from the Archaean, the period during which the foundations of the Earth were laid down. The 2.7 Ga Belingwe Greenstone Belt in Zimbabwe has proved to be valuable because it has some of the best-preserved Archaean stratigraphy in the world. An unconformity between sialic basement and supracrustal rocks of the greenstone belt, and exotic rocks such as komatiites and stromatolites, are immensely contributing towards the knowledge about the evolution of the young Earth and the beginning of life. The frequent use of the Belingwe Greenstone Belt examples to explain geotectonic processes of the early Earth give testimony to the importance of this structure. Interpretation of some of the features of the greenstone belt is sometimes controversial, which forms areas of endless research to better understand the Archaean Era. It is for these reasons that arguments are presented for consideration of the Belingwe Greenstone Belt as a national Geoheritage site.
地质过程的产物，如岩层、非地层、结构、矿物、化石和地貌，是地球演变的独特记录。这些形成了一幅连贯的图画，展示了地球是如何演变的。随着年代的久远，这幅图画变得模糊不清。因此，从太古宙（地球基础奠定时期）收集信息面临挑战。津巴布韦的 2.7 Ga Belingwe 绿岩带被证明是非常有价值的，因为这里有世界上保存最完好的太古宙地层。该绿岩带的硅质基底岩和超壳岩之间的不整合以及奇特的岩石（如珂玛蒂岩和叠层岩）对了解年轻地球的演化和生命的起源做出了巨大贡献。贝林圭绿岩带的例子经常被用来解释早期地球的大地构造过程，这证明了这一结构的重要性。对绿岩带某些特征的解释有时会引起争议，这就形成了无休止的研究领域，以便更好地了解太古宙。正是出于这些原因，我们提出了将贝林圭绿岩带视为国家地质遗产地的论点。
{"title":"The value of the Belingwe Greenstone Belt, Zimbabwe, as a national Geoheritage site","authors":"Forbes Mugumbate","doi":"10.1144/sp543-2022-244","DOIUrl":"https://doi.org/10.1144/sp543-2022-244","url":null,"abstract":"\u0000 Products of geological processes such as rock formations, unconformities, structures, minerals, fossils, and landforms, represent unique records of the evolution of the Earth. These form a coherent picture showing how the Earth evolved. The picture becomes blurred with antiquity. Consequently, there are challenges in gathering information from the Archaean, the period during which the foundations of the Earth were laid down. The 2.7 Ga Belingwe Greenstone Belt in Zimbabwe has proved to be valuable because it has some of the best-preserved Archaean stratigraphy in the world. An unconformity between sialic basement and supracrustal rocks of the greenstone belt, and exotic rocks such as komatiites and stromatolites, are immensely contributing towards the knowledge about the evolution of the young Earth and the beginning of life. The frequent use of the Belingwe Greenstone Belt examples to explain geotectonic processes of the early Earth give testimony to the importance of this structure. Interpretation of some of the features of the greenstone belt is sometimes controversial, which forms areas of endless research to better understand the Archaean Era. It is for these reasons that arguments are presented for consideration of the Belingwe Greenstone Belt as a national Geoheritage site.","PeriodicalId":281618,"journal":{"name":"Geological Society, London, Special Publications","volume":"72 12","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140238302","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
K. Boukhalfa, M. Soussi, J. Reynaud, Santanu Banerjee
The Lower Cretaceous deposits of North Africa represent a terrestrial to shallow marine sandstone-dominated succession often referred to as the “Continental Intercalaire” (CI) and Nubian Sandstone (NS) informal groups. The upper Barremian Sidi Aich Formation of the CI is distinguished throughout the Chotts basin of southern Tunisia by sandstone-dominated sequences within conglomerate, calcareous siltstone, and paleosol red-bed occurrences. This paper aims to highlight: ( i ) the facies distribution, internal architecture and depositional environment of sandbodies, and ( ii ) the origin, spatial distribution and architecture of red beds that underlined and topped sandbodies. Strata at the Zimlet El Beida anticlinal structure (ZBAS), Chotts basin, offer a good opportunity for detailed field observations and bed-by-bed logging of three representative lithostratigraphical sections. Detailed sedimentological investigation allows the recognition of several lithofacies grouped into three facies associations indicating tidal flat, tidal channel and tidal bars depositional settings characterizing a transgressive tide-dominated estuarine system that developed during an episode of relative sea‐level fluctuations at the Lower Cretaceous. The high-resolution petrographical, mineralogical and geochemical analyses of red beds allow differentiation of three distinguished lithofacies sets including (i) intraformational conglomerates, (ii) calcareous siltstones and (iii) paleosol. Major red beds comprise detrital grains inherited from the host or parent sediment and authigenic minerals (dolomite, calcite, and hematite) precipitated during the diagenetic processes. Grain components have been partially or completely cemented and/ or replaced by terrestrial phreatic dolomite. The negative signatures of δ 13 C and δ 18 O of the dolomite analyses indicate that dolomitization processes have been influenced by fluctuations of the groundwater table or climate change from semi-arid to semi-humid conditions. This study, therefore, may provide useful data for the better understanding of the internal architecture of the red beds associated to sandbodies which represented the main and significant potential reservoir within the Lower Cretaceous CI sandstone-dominated groundwater aquifers of the Chotts basin.
北非的下白垩统沉积代表了陆地至浅海砂岩为主的演替，通常被称为 "大陆间"（CI）和努比亚砂岩（NS）非正式组。在突尼斯南部的乔茨盆地，CI 的上巴利米亚统 Sidi Aich 地层以砾岩、钙质粉砂岩和古沉积红床地层中的砂岩为主。本文旨在强调：(i) 砂体的面状分布、内部结构和沉积环境；(ii) 砂体下部和顶部红床的起源、空间分布和结构。Chotts 盆地 Zimlet El Beida 反斜面结构（ZBAS）的地层为对三个具有代表性的岩层剖面进行详细的实地观察和逐层测井提供了良机。通过详细的沉积学调查，可以识别出分为三个岩相组合的几种岩性，这三个岩相组合显示了潮平带、潮汐通道和潮汐条带沉积环境的特征，即在下白垩统海平面相对波动期间形成的以潮汐为主的横向河口系统。通过对红海床进行高分辨率岩石学、矿物学和地球化学分析，可以区分出三组不同的岩性，包括（i）构造内砾岩、（ii）钙质粉砂岩和（iii）古溶岩。主要的红床包括从主沉积物或母体沉积物中继承下来的碎屑颗粒，以及在成岩过程中析出的自生矿物（白云石、方解石和赤铁矿）。颗粒成分部分或全部被陆相白云岩胶结和/或取代。白云石分析中 δ 13 C 和 δ 18 O 的负特征表明，白云石化过程受到地下水位波动或从半干旱到半湿润的气候变化的影响。因此，这项研究可为更好地了解与砂体相关的红床内部结构提供有用的数据，而砂体是乔茨盆地下白垩统 CI 砂岩为主的地下水含水层中主要和重要的潜在储层。
{"title":"Sandstones and red-beds in the Lower Cretaceous Sidi Aich Formation, Chotts basin (Southern Tunisia): Facies, architecture and depositional environments","authors":"K. Boukhalfa, M. Soussi, J. Reynaud, Santanu Banerjee","doi":"10.1144/sp545-2023-181","DOIUrl":"https://doi.org/10.1144/sp545-2023-181","url":null,"abstract":"\u0000 \u0000 The Lower Cretaceous deposits of North Africa represent a terrestrial to shallow marine sandstone-dominated succession often referred to as the “Continental Intercalaire” (CI) and Nubian Sandstone (NS) informal groups. The upper Barremian Sidi Aich Formation of the CI is distinguished throughout the Chotts basin of southern Tunisia by sandstone-dominated sequences within conglomerate, calcareous siltstone, and paleosol red-bed occurrences. This paper aims to highlight: (\u0000 i\u0000 ) the facies distribution, internal architecture and depositional environment of sandbodies, and (\u0000 ii\u0000 ) the origin, spatial distribution and architecture of red beds that underlined and topped sandbodies. Strata at the Zimlet El Beida anticlinal structure (ZBAS), Chotts basin, offer a good opportunity for detailed field observations and bed-by-bed logging of three representative lithostratigraphical sections. Detailed sedimentological investigation allows the recognition of several lithofacies grouped into three facies associations indicating tidal flat, tidal channel and tidal bars depositional settings characterizing a transgressive tide-dominated estuarine system that developed during an episode of relative sea‐level fluctuations at the Lower Cretaceous. The high-resolution petrographical, mineralogical and geochemical analyses of red beds allow differentiation of three distinguished lithofacies sets including (i) intraformational conglomerates, (ii) calcareous siltstones and (iii) paleosol. Major red beds comprise detrital grains inherited from the host or parent sediment and authigenic minerals (dolomite, calcite, and hematite) precipitated during the diagenetic processes. Grain components have been partially or completely cemented and/ or replaced by terrestrial phreatic dolomite. The negative signatures of δ\u0000 13\u0000 C and δ\u0000 18\u0000 O of the dolomite analyses indicate that dolomitization processes have been influenced by fluctuations of the groundwater table or climate change from semi-arid to semi-humid conditions. This study, therefore, may provide useful data for the better understanding of the internal architecture of the red beds associated to sandbodies which represented the main and significant potential reservoir within the Lower Cretaceous CI sandstone-dominated groundwater aquifers of the Chotts basin.\u0000","PeriodicalId":281618,"journal":{"name":"Geological Society, London, Special Publications","volume":"80 8","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140241839","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Louis L. Jacobs, S. Schröder, Nair de Sousa, R. Dixon, E. Fiordalisi, Arthur Marechal, Octávio Mateus, Pedro Claude Nsungani, M. Polcyn, Gustavo do Couto Ramos Pereira, N. Rochelle-Bates, A. Schulp, C. Scotese, I. Sharp, Carlos Gaudari Silvano, R. Swart, Diana P. Vineyard
The jigsaw-puzzle fit of South America and Africa is an icon of plate tectonics and continental drift. Fieldwork in Angola since 2002 allows the correlation of onshore outcrops and offshore geophysical and well-core data in the context of rift, sag, salt, and post-salt drift phases of the opening of the central South Atlantic. These outcrops, ranging in age from >130 Ma to <71 Ma, record Early Cretaceous outpouring of the Etendeka-Paraná Large Igneous Province (Bero Volcanic Complex) and rifting, followed by continental carbonate and siliciclastic deposition (Tumbalunda Formation) during the sagging of the nascent central South Atlantic basin. By the Aptian, evaporation of sea water resulted in thick salt deposits (Bambata Formation), terminated by sea floor spreading. The Equatorial Atlantic Gateway began opening by the early Late Cretaceous (100 Ma) and allowed flow of currents between the North and South Atlantic, creating environmental conditions that heralded the introduction of marine reptiles. These dramatic outcrops are a unique element of geoheritage because they arguably comprise the most complete terrestrially exposed geological record of the puzzle-like icon of continental drift.
南美洲和非洲的拼图组合是板块构造和大陆漂移的标志。自 2002 年以来，在安哥拉进行的实地考察使我们能够在南大西洋中部开裂、下陷、盐和后盐漂移阶段的背景下，将陆上露头与近海地球物理和井芯数据联系起来。这些露头的年龄从大于 130 Ma 到小于 71 Ma 不等，记录了早白垩世埃顿德卡-巴拉那大火成岩省（贝罗火山群）的喷发和断裂，随后在新生的南大西洋中部海盆下陷过程中出现了大陆碳酸盐和硅质沉积（图姆巴伦达构造）。到了始新世，海水蒸发形成了厚厚的盐沉积（班巴塔地层），并因海底扩张而结束。赤道大西洋门户在晚白垩世早期（100Ma）开始打开，北大西洋和南大西洋之间的洋流得以流动，为海洋爬行动物的出现创造了环境条件。这些引人注目的露头是地质遗产的一个独特元素，因为它们可以说是最完整的陆地裸露地质记录，是大陆漂移的拼图式图标。
{"title":"The Atlantic jigsaw puzzle and the geoheritage of Angola","authors":"Louis L. Jacobs, S. Schröder, Nair de Sousa, R. Dixon, E. Fiordalisi, Arthur Marechal, Octávio Mateus, Pedro Claude Nsungani, M. Polcyn, Gustavo do Couto Ramos Pereira, N. Rochelle-Bates, A. Schulp, C. Scotese, I. Sharp, Carlos Gaudari Silvano, R. Swart, Diana P. Vineyard","doi":"10.1144/sp543-2022-301","DOIUrl":"https://doi.org/10.1144/sp543-2022-301","url":null,"abstract":"\u0000 The jigsaw-puzzle fit of South America and Africa is an icon of plate tectonics and continental drift. Fieldwork in Angola since 2002 allows the correlation of onshore outcrops and offshore geophysical and well-core data in the context of rift, sag, salt, and post-salt drift phases of the opening of the central South Atlantic. These outcrops, ranging in age from >130 Ma to <71 Ma, record Early Cretaceous outpouring of the Etendeka-Paraná Large Igneous Province (Bero Volcanic Complex) and rifting, followed by continental carbonate and siliciclastic deposition (Tumbalunda Formation) during the sagging of the nascent central South Atlantic basin. By the Aptian, evaporation of sea water resulted in thick salt deposits (Bambata Formation), terminated by sea floor spreading. The Equatorial Atlantic Gateway began opening by the early Late Cretaceous (100 Ma) and allowed flow of currents between the North and South Atlantic, creating environmental conditions that heralded the introduction of marine reptiles. These dramatic outcrops are a unique element of geoheritage because they arguably comprise the most complete terrestrially exposed geological record of the puzzle-like icon of continental drift.","PeriodicalId":281618,"journal":{"name":"Geological Society, London, Special Publications","volume":"84 2‐3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140256979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Middle Eastern carbonate petroleum reservoirs exhibit a range of heterogeneities which consist of variable combinations of primary stratigraphic and secondary diagenetic and structural characteristics. These produce diverse permeability architectures which can exert a profound influence on reservoir performance during secondary recovery. Of particular importance are laterally persistent discrete zones of elevated permeability (DZEP) that typically make up a volumetrically minor proportion of the reservoir yet show disproportionately high fluid inflow or outflow. The stratigraphic, diagenetic, and structural origins of elevated permeability in Middle Eastern carbonate reservoirs are considered here and the consequences of such features for reservoir performance are discussed. The term DZEP denotes geological sources of elevated permeability at least an order of magnitude greater than background reservoir properties. Stratigraphically organised DZEP comprise coarse-grained layers, event beds or parasequence tops or bases in neritic or platform interior settings. Other origins include bioturbated layers, grainy clinothems, and bed-scale, grain-size variations in shoal deposits. Diagenetic DZEP are typically dissolution horizons with mouldic and touching-vug pore networks or dolomitized intervals which often overprint stratigraphic DZEP. Structural DZEP include individual faults, fracture corridors, and fracture concentrations related to mechanical stratigraphy. During production through natural pressure depletion, DZEP may dominate well productivity. Under secondary recovery, the same intervals may dominate inter-well fluid flow, causing flood conformance issues, cross-zone fluid movement, bypassed pay, and earlier-than-expected water or gas breakthrough to production wells. Optimisation of production and ultimate recovery relies on collecting the correct kinds of data at a sufficiently early stage in the reservoir characterisation process to permit their inclusion in static and dynamic reservoir models.
{"title":"Middle Eastern carbonate reservoirs – the critical impact of Discrete Zones of Elevated Permeability (DZEP) on reservoir performance","authors":"Nigel E. Cross, T.P. Burchette","doi":"10.1144/sp548-2023-144","DOIUrl":"https://doi.org/10.1144/sp548-2023-144","url":null,"abstract":"\u0000 Middle Eastern carbonate petroleum reservoirs exhibit a range of heterogeneities which consist of variable combinations of primary stratigraphic and secondary diagenetic and structural characteristics. These produce diverse permeability architectures which can exert a profound influence on reservoir performance during secondary recovery. Of particular importance are laterally persistent discrete zones of elevated permeability (DZEP) that typically make up a volumetrically minor proportion of the reservoir yet show disproportionately high fluid inflow or outflow. The stratigraphic, diagenetic, and structural origins of elevated permeability in Middle Eastern carbonate reservoirs are considered here and the consequences of such features for reservoir performance are discussed.\u0000 The term DZEP denotes geological sources of elevated permeability at least an order of magnitude greater than background reservoir properties. Stratigraphically organised DZEP comprise coarse-grained layers, event beds or parasequence tops or bases in neritic or platform interior settings. Other origins include bioturbated layers, grainy clinothems, and bed-scale, grain-size variations in shoal deposits. Diagenetic DZEP are typically dissolution horizons with mouldic and touching-vug pore networks or dolomitized intervals which often overprint stratigraphic DZEP. Structural DZEP include individual faults, fracture corridors, and fracture concentrations related to mechanical stratigraphy.\u0000 During production through natural pressure depletion, DZEP may dominate well productivity. Under secondary recovery, the same intervals may dominate inter-well fluid flow, causing flood conformance issues, cross-zone fluid movement, bypassed pay, and earlier-than-expected water or gas breakthrough to production wells. Optimisation of production and ultimate recovery relies on collecting the correct kinds of data at a sufficiently early stage in the reservoir characterisation process to permit their inclusion in static and dynamic reservoir models.","PeriodicalId":281618,"journal":{"name":"Geological Society, London, Special Publications","volume":"30 7","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140259667","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Lovecchio, M. Abdelmalak, S. Planke, Ofelia Silio, S. Rohais, Sebastián Arismendi, Emilio A. Rojas Vera, D. Kulhanek, N. Bolatti, Victor A. Ramos
The opening of the South Atlantic Ocean in the Early Cretaceous was only the final stage of the complex rifting process of SW Gondwana. In this contribution we reassess the chronology of Mesozoic basin formation in southern South America and Africa and integrate it in the long-term rifting and breakup history of SW Gondwana. During the Triassic, after the Gondwanides orogeny, plate-scale instabilities produced intracontinental rifting in Africa, and retro-arc extension on the SW-margin of Gondwana. This process was followed and accentuated by the impingement of the Karoo plume in the Early Jurassic, which triggered rifting in East Africa and ultimately produced the breakup of Eastern from Western Gondwana in the Middle Jurassic. Retroarc extension continued affecting the paleo-Pacific margin, with emplacement of the Chon Aike magmatic province in the Patagonian retro-arc during the Early-Middle Jurassic. By the Late Jurassic retroarc rifting reached a point of oceanic crust accretion, with the establishment of the Rocas Verdes back-arc basin in southern Patagonia, together with the formation of the Weddell Sea further south, between the South American plate and Antarctica. The core of the Late Paleozoic Gondwanides orogen, between southern South America and Africa, was subjected to oblique rifting at this time and produced the Outeniqua and Rawson/Valdés basins. This area was the locus of extension and oceanization in the Early Cretaceous associated with a rotation of the stress field from NE-SW to E-W extension. The formation of the South Atlantic Ocean resulted from lithospheric extension and was accompanied by extensive intrusive magmatism and extrusive flood basalts identified as seaward dipping reflectors (SDRs), which were emplaced diachronically from south to north, along different segments along both conjugate margins. These volcanic rocks form the South Atlantic Large Igneous Province. The chronology of the South Atlantic opening and the magmatic sources and processes associated with SDR formation remain interpretative since they have only been studied on seismic data but are still undrilled, hence scientific drilling will be key to unravel many of these unknowns.
{"title":"Mesozoic Rifting in SW Gondwana and Breakup of the Southern South Atlantic Ocean","authors":"J. Lovecchio, M. Abdelmalak, S. Planke, Ofelia Silio, S. Rohais, Sebastián Arismendi, Emilio A. Rojas Vera, D. Kulhanek, N. Bolatti, Victor A. Ramos","doi":"10.1144/sp547-2023-140","DOIUrl":"https://doi.org/10.1144/sp547-2023-140","url":null,"abstract":"\u0000 The opening of the South Atlantic Ocean in the Early Cretaceous was only the final stage of the complex rifting process of SW Gondwana. In this contribution we reassess the chronology of Mesozoic basin formation in southern South America and Africa and integrate it in the long-term rifting and breakup history of SW Gondwana. During the Triassic, after the Gondwanides orogeny, plate-scale instabilities produced intracontinental rifting in Africa, and retro-arc extension on the SW-margin of Gondwana. This process was followed and accentuated by the impingement of the Karoo plume in the Early Jurassic, which triggered rifting in East Africa and ultimately produced the breakup of Eastern from Western Gondwana in the Middle Jurassic.\u0000 \u0000 Retroarc extension continued affecting the paleo-Pacific margin, with emplacement of the Chon Aike magmatic province in the Patagonian retro-arc during the Early-Middle Jurassic. By the Late Jurassic retroarc rifting reached a point of oceanic crust accretion, with the establishment of the Rocas Verdes back-arc basin in southern Patagonia, together with the formation of the Weddell Sea further south, between the South American plate and Antarctica. The core of the Late Paleozoic Gondwanides orogen, between southern South America and Africa, was subjected to oblique rifting at this time and produced the Outeniqua and Rawson/Valdés basins. This area was the\u0000 locus\u0000 of extension and oceanization in the Early Cretaceous associated with a rotation of the stress field from NE-SW to E-W extension.\u0000 \u0000 The formation of the South Atlantic Ocean resulted from lithospheric extension and was accompanied by extensive intrusive magmatism and extrusive flood basalts identified as seaward dipping reflectors (SDRs), which were emplaced diachronically from south to north, along different segments along both conjugate margins. These volcanic rocks form the South Atlantic Large Igneous Province. The chronology of the South Atlantic opening and the magmatic sources and processes associated with SDR formation remain interpretative since they have only been studied on seismic data but are still undrilled, hence scientific drilling will be key to unravel many of these unknowns.","PeriodicalId":281618,"journal":{"name":"Geological Society, London, Special Publications","volume":"28 12","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140262689","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. E. Jelby, S. Grundvåg, K. Śliwińska, P. Alsen, Madeleine L. Vickers, S. Olaussen, Lars Stemmerik
Lower Cretaceous stratigraphy of the high palaeo-latitude Arctic-Boreal Realm is generally more poorly understood than its lower-latitude Tethyan counterpart, prohibiting regional correlations and evaluation of global climate dynamics during this important high- p CO 2 period. In this paper, a holostratigraphic scheme and lithostratigraphic revision are presented for the Valanginian-lower Barremian, siliciclastic ramp succession of the Rurikfjellet Formation in Svalbard, drawn from synthesis of the latest published sedimentological, biostratigraphic, petrophysical, sequence stratigraphic, chemostratigraphic and chronostratigraphic results, supplemented by new measured sections from five localities. The offshore mudstone-dominated Wimanfjellet Member (Valanginian-lower Barremian) is retained, whereas three new members are defined according to their distinct geographic, sedimentological and stratigraphic characteristics: The Adventpynten Member (upper(?) Valanginian-lowermost upper Hauterivian) constitutes a thick, relatively localized succession of mass-transport deposits. The Kikutodden Member (Hauterivian-lower Barremian) is discarded and replaced by the northern Bohemanneset Member and southern Fotografryggen Member, representing respectively: heterogeneous prodelta to delta front deposits; and sandy offshore transition to shoreface deposits. The Rurikfjellet Formation records Valanginian-earliest late Hauterivian shoreline progradation followed by late Hauterivian-early Barremian shoreline retreat and flooding across a low-gradient ramp, which never experienced full regression into continental deposits within the extent of the present-day outcrop belt.
{"title":"Lower Cretaceous holostratigraphy in Svalbard: the Arctic key piece of the Boreal basin puzzle","authors":"M. E. Jelby, S. Grundvåg, K. Śliwińska, P. Alsen, Madeleine L. Vickers, S. Olaussen, Lars Stemmerik","doi":"10.1144/sp545-2023-177","DOIUrl":"https://doi.org/10.1144/sp545-2023-177","url":null,"abstract":"\u0000 \u0000 Lower Cretaceous stratigraphy of the high palaeo-latitude Arctic-Boreal Realm is generally more poorly understood than its lower-latitude Tethyan counterpart, prohibiting regional correlations and evaluation of global climate dynamics during this important high-\u0000 p\u0000 CO\u0000 2\u0000 period. In this paper, a holostratigraphic scheme and lithostratigraphic revision are presented for the Valanginian-lower Barremian, siliciclastic ramp succession of the Rurikfjellet Formation in Svalbard, drawn from synthesis of the latest published sedimentological, biostratigraphic, petrophysical, sequence stratigraphic, chemostratigraphic and chronostratigraphic results, supplemented by new measured sections from five localities. The offshore mudstone-dominated Wimanfjellet Member (Valanginian-lower Barremian) is retained, whereas three new members are defined according to their distinct geographic, sedimentological and stratigraphic characteristics: The Adventpynten Member (upper(?) Valanginian-lowermost upper Hauterivian) constitutes a thick, relatively localized succession of mass-transport deposits. The Kikutodden Member (Hauterivian-lower Barremian) is discarded and replaced by the northern Bohemanneset Member and southern Fotografryggen Member, representing respectively: heterogeneous prodelta to delta front deposits; and sandy offshore transition to shoreface deposits. The Rurikfjellet Formation records Valanginian-earliest late Hauterivian shoreline progradation followed by late Hauterivian-early Barremian shoreline retreat and flooding across a low-gradient ramp, which never experienced full regression into continental deposits within the extent of the present-day outcrop belt.\u0000","PeriodicalId":281618,"journal":{"name":"Geological Society, London, Special Publications","volume":"73 10","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140266343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fritz-Lukas Stoepke, Annette E. Götz, M. Blumenberg, Julia Gravendyck, J. Erbacher, Roberto Pierau, R. Schöner, U. Heimhofer
In the Lower Saxony Basin (LSB) of Northern Germany, the earliest Cretaceous (Berriasian, “German Wealden”) is represented by organic-rich shales assigned to the Isterberg Fm., which have been deposited under brackish-lacustrine conditions in a partially restricted basin. Towards the southern basin margin, these shales interfinger with nearshore sandstones sourced from the Deister-Hils delta. In order to better understand the environmental conditions and depositional dynamics of the Isterberg Fm., the sedimentary organic matter (OM) has been studied with a combined approach including bulk rock organic geochemistry and palynofacies analysis. The lower part (W1–W3) is interpreted to reflect very shallow water conditions and episodic emergence, indicated by multiple occurrences of palaesol horizons, rhizoliths and intercalated coal beds formed within a mud-dominated and protected domain of the delta plain. The overlying sand-rich interval represents a nearshore deltaic setting. A distinct change is observed in the upper part (W4), indicating more distal conditions characterised by clay dominated sedimentation, abundant lumachelle interbeds and a predominance of aquatic-derived OM. The newly acquired data fill a gap in the record between proximal and distal strata of the Berriasian LSB and provide new insights into the accumulation and preservation of OM within this exceptional depositional setting. Supplementary material at https://doi.org/10.6084/m9.figshare.c.7093491
{"title":"Composition and distribution of sedimentary organic matter in nearshore Berriasian strata (“German Wealden”) of the eastern Lower Saxony Basin, NW Germany","authors":"Fritz-Lukas Stoepke, Annette E. Götz, M. Blumenberg, Julia Gravendyck, J. Erbacher, Roberto Pierau, R. Schöner, U. Heimhofer","doi":"10.1144/sp545-2023-157","DOIUrl":"https://doi.org/10.1144/sp545-2023-157","url":null,"abstract":"\u0000 In the Lower Saxony Basin (LSB) of Northern Germany, the earliest Cretaceous (Berriasian, “German Wealden”) is represented by organic-rich shales assigned to the Isterberg Fm., which have been deposited under brackish-lacustrine conditions in a partially restricted basin. Towards the southern basin margin, these shales interfinger with nearshore sandstones sourced from the Deister-Hils delta. In order to better understand the environmental conditions and depositional dynamics of the Isterberg Fm., the sedimentary organic matter (OM) has been studied with a combined approach including bulk rock organic geochemistry and palynofacies analysis. The lower part (W1–W3) is interpreted to reflect very shallow water conditions and episodic emergence, indicated by multiple occurrences of palaesol horizons, rhizoliths and intercalated coal beds formed within a mud-dominated and protected domain of the delta plain. The overlying sand-rich interval represents a nearshore deltaic setting. A distinct change is observed in the upper part (W4), indicating more distal conditions characterised by clay dominated sedimentation, abundant lumachelle interbeds and a predominance of aquatic-derived OM. The newly acquired data fill a gap in the record between proximal and distal strata of the Berriasian LSB and provide new insights into the accumulation and preservation of OM within this exceptional depositional setting.\u0000 \u0000 Supplementary material at\u0000 https://doi.org/10.6084/m9.figshare.c.7093491\u0000","PeriodicalId":281618,"journal":{"name":"Geological Society, London, Special Publications","volume":"30 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140412342","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Zhoukoudian (Choukoutien) site, which was excavated in 1921, is one of the most important ancient human sites in China and in the world as well. From the perspective of the history of transnational science, this paper summarizes the history of the excavation of Zhoukoudian and the research that has been done into related fossil and human remains. It argues that Zhoukoudian was the birthplace of Paleoanthropology and the stimulus for the establishment of Paleolithic archaeology as a field in China. The Zhoukoudian site preserves traces of prehistoric human activities that date from 700,000 to 10,000 years ago, including human fossils, stone artifacts, ornaments, and mammalian fossils, thus it still remains the most abundant, systematic and valuable site of its kind in the world, as well as being a very important geoheritage site.
{"title":"Zhoukoudian: The Birthplace of Paleoanthropology and the Stimulus for Paleolithic Archeology in China","authors":"Chengsheng Sun","doi":"10.1144/sp543-2022-272","DOIUrl":"https://doi.org/10.1144/sp543-2022-272","url":null,"abstract":"\u0000 The Zhoukoudian (Choukoutien) site, which was excavated in 1921, is one of the most important ancient human sites in China and in the world as well. From the perspective of the history of transnational science, this paper summarizes the history of the excavation of Zhoukoudian and the research that has been done into related fossil and human remains. It argues that Zhoukoudian was the birthplace of Paleoanthropology and the stimulus for the establishment of Paleolithic archaeology as a field in China. The Zhoukoudian site preserves traces of prehistoric human activities that date from 700,000 to 10,000 years ago, including human fossils, stone artifacts, ornaments, and mammalian fossils, thus it still remains the most abundant, systematic and valuable site of its kind in the world, as well as being a very important geoheritage site.","PeriodicalId":281618,"journal":{"name":"Geological Society, London, Special Publications","volume":"89 8","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140423844","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Some significant geologic sites are inaccessible. Among the most inaccessible sites are the hydrothermal vents and their associated biologic communities located deep in the ocean. These prime geoheritage sites, hosting what may be the most primordial life on Earth, are vulnerable to mineral and fishing exploitation. Many lie in international waters, protected only by non-binding agreements with no clearly defined means of enforcement. The discovery of these vents in 1977 fundamentally altered scientists' view of basic Earth processes and the extreme conditions under which life can exist. The discovery of the vents was a group effort and required technological accomplishments not available to previous generations of researchers. Often overlooked in the credits for this discovery was the persistence and determination of Kathleen Crane, a graduate student at Scripps Institution of Oceanography. Many women of her era faced significant challenges as they attempted to break into an often unwelcoming field, marine geology. The challenges were not unique to geology; women were not welcomed in many other disciplines both scientific and non-scientific. In spite of the obstacles, few people have made as remarkable a geoscience discovery as Dr. Crane.
{"title":"Geoheritage in the Making: The discovery and vulnerability of Deep-Sea Hydrothermal Vents","authors":"Suzanne OConnell","doi":"10.1144/sp543-2022-293","DOIUrl":"https://doi.org/10.1144/sp543-2022-293","url":null,"abstract":"\u0000 Some significant geologic sites are inaccessible. Among the most inaccessible sites are the hydrothermal vents and their associated biologic communities located deep in the ocean. These prime geoheritage sites, hosting what may be the most primordial life on Earth, are vulnerable to mineral and fishing exploitation. Many lie in international waters, protected only by non-binding agreements with no clearly defined means of enforcement. The discovery of these vents in 1977 fundamentally altered scientists' view of basic Earth processes and the extreme conditions under which life can exist. The discovery of the vents was a group effort and required technological accomplishments not available to previous generations of researchers. Often overlooked in the credits for this discovery was the persistence and determination of Kathleen Crane, a graduate student at Scripps Institution of Oceanography. Many women of her era faced significant challenges as they attempted to break into an often unwelcoming field, marine geology. The challenges were not unique to geology; women were not welcomed in many other disciplines both scientific and non-scientific. In spite of the obstacles, few people have made as remarkable a geoscience discovery as Dr. Crane.","PeriodicalId":281618,"journal":{"name":"Geological Society, London, Special Publications","volume":"77 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140424136","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：