J. Frieling, E. Huurdeman, Charlotte C M Rem, T. Donders, J. Pross, S. Bohaty, G. Holdgate, S. Gallagher, B. Mcgowran, P. Bijl
Abstract. Detailed, stratigraphically well-constrained environmental reconstructions are available for Paleocene and Eocene strata at a range of sites in the southwest Pacific Ocean (New Zealand and East Tasman Plateau; ETP) and Integrated Ocean Discovery Program (IODP) Site U1356 in the south of the Australo-Antarctic Gulf (AAG). These reconstructions have revealed a large discrepancy between temperature proxy data and climate models in this region, suggesting a crucial error in model, proxy data or both. To resolve the origin of this discrepancy, detailed reconstructions are needed from both sides of the Tasmanian Gateway. Paleocene–Eocene sedimentary archives from the west of the Tasmanian Gateway have unfortunately remained scarce (only IODP Site U1356), and no well-dated successions are available for the northern sector of the AAG. Here we present new stratigraphic data for upper Paleocene and lower Eocene strata from the Otway Basin, southeast Australia, on the (north)west side of the Tasmanian Gateway. We analyzed sediments recovered from exploration drilling (Latrobe-1 drill core) and outcrop sampling (Point Margaret) and performed high-resolution carbon isotope geochemistry of bulk organic matter and dinoflagellate cyst (dinocyst) and pollen biostratigraphy on sediments from the regional lithostratigraphic units, including the Pebble Point Formation, Pember Mudstone and Dilwyn Formation. Pollen and dinocyst assemblages are assigned to previously established Australian pollen and dinocyst zonations and tied to available zonations for the SW Pacific. Based on our dinocyst stratigraphy and previously published planktic foraminifer biostratigraphy, the Pebble Point Formation at Point Margaret is dated to the latest Paleocene. The globally synchronous negative carbon isotope excursion that marks the Paleocene–Eocene boundary is identified within the top part of the Pember Mudstone in the Latrobe-1 borehole and at Point Margaret. However, the high abundances of the dinocyst Apectodinium prior to this negative carbon isotope excursion prohibit a direct correlation of this regional bio-event with the quasi-global Apectodinium acme at the Paleocene–Eocene Thermal Maximum (PETM; 56 Ma ). Therefore, the first occurrence of the pollen species Spinizonocolpites prominatus and the dinocyst species Florentinia reichartii are here designated as regional markers for the PETM. In the Latrobe-1 drill core, dinocyst biostratigraphy further indicates that the early Eocene ( ∼ 56–51 Ma ) sediments are truncated by a ∼ 10 Myr long hiatus overlain by middle Eocene ( ∼ 40 Ma ) strata. These sedimentary archives from southeast Australia may prove key in resolving the model–data discrepancy in this region, and the new stratigraphic data presented here allow for detailed comparisons between paleoclimate records on both sides of the Tasmanian Gateway.
{"title":"Identification of the Paleocene–Eocene boundary in coastal strata in the Otway Basin, Victoria, Australia","authors":"J. Frieling, E. Huurdeman, Charlotte C M Rem, T. Donders, J. Pross, S. Bohaty, G. Holdgate, S. Gallagher, B. Mcgowran, P. Bijl","doi":"10.5194/JM-37-317-2018","DOIUrl":"https://doi.org/10.5194/JM-37-317-2018","url":null,"abstract":"Abstract. Detailed, stratigraphically well-constrained environmental reconstructions\u0000are available for Paleocene and Eocene strata at a range of sites in the\u0000southwest Pacific Ocean (New Zealand and East Tasman Plateau; ETP) and\u0000Integrated Ocean Discovery Program (IODP) Site U1356 in the south of the\u0000Australo-Antarctic Gulf (AAG). These reconstructions have revealed a large\u0000discrepancy between temperature proxy data and climate models in this region,\u0000suggesting a crucial error in model, proxy data or both. To resolve the\u0000origin of this discrepancy, detailed reconstructions are needed from both\u0000sides of the Tasmanian Gateway. Paleocene–Eocene sedimentary archives from\u0000the west of the Tasmanian Gateway have unfortunately remained scarce (only\u0000IODP Site U1356), and no well-dated successions are available for the\u0000northern sector of the AAG. Here we present new stratigraphic data for upper\u0000Paleocene and lower Eocene strata from the Otway Basin, southeast Australia,\u0000on the (north)west side of the Tasmanian Gateway. We analyzed sediments\u0000recovered from exploration drilling (Latrobe-1 drill core) and outcrop\u0000sampling (Point Margaret) and performed high-resolution carbon isotope\u0000geochemistry of bulk organic matter and dinoflagellate cyst (dinocyst) and\u0000pollen biostratigraphy on sediments from the regional lithostratigraphic\u0000units, including the Pebble Point Formation, Pember Mudstone and Dilwyn\u0000Formation. Pollen and dinocyst assemblages are assigned to previously\u0000established Australian pollen and dinocyst zonations and tied to available\u0000zonations for the SW Pacific. Based on our dinocyst stratigraphy and\u0000previously published planktic foraminifer biostratigraphy, the Pebble Point\u0000Formation at Point Margaret is dated to the latest Paleocene. The globally\u0000synchronous negative carbon isotope excursion that marks the\u0000Paleocene–Eocene boundary is identified within the top part of the Pember\u0000Mudstone in the Latrobe-1 borehole and at Point Margaret. However, the high abundances of the\u0000dinocyst Apectodinium prior to this negative carbon isotope\u0000excursion prohibit a direct correlation of this regional bio-event with the\u0000quasi-global Apectodinium acme at the Paleocene–Eocene Thermal\u0000Maximum (PETM; 56 Ma ). Therefore, the first occurrence of the pollen\u0000species Spinizonocolpites prominatus and the dinocyst species\u0000Florentinia reichartii are here designated as regional markers for\u0000the PETM. In the Latrobe-1 drill core, dinocyst biostratigraphy further\u0000indicates that the early Eocene ( ∼ 56–51 Ma ) sediments are\u0000truncated by a ∼ 10 Myr long hiatus overlain by middle Eocene\u0000( ∼ 40 Ma ) strata. These sedimentary archives from southeast\u0000Australia may prove key in resolving the model–data discrepancy in this\u0000region, and the new stratigraphic data presented here allow for detailed\u0000comparisons between paleoclimate records on both sides of the Tasmanian\u0000Gateway.","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2018-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49326870","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Dunay, W. Braham, M. K. E. Cooper, Martin Lester, F. Tremolada
Abstract. Tectonic models suggest the absence of a deep water connection on the Mozambique Ridge during early Neocomian time. These models imply the initiation of a deep water connection between the southern Atlantic and Indian oceans formed during Barremian–earliest Aptian times. However, previous biostratigraphic studies of the earliest deep water sediments on the Mozambique Ridge suggest that the basal section is Neocomian in age. Here, we present a new biostratigraphic analysis undertaken to test this tectonic model and determine the earliest age of deep water sedimentation on the Mozambique Ridge. Core samples from the Cretaceous interval 222.05–406.32 m (Cores 19–32) of DSDP Site 249, Leg 25, were sampled for calcareous nannoplankton and palynological analysis. Most of the sampling was concentrated on the Lower Cretaceous interval below 294 m . Our results indicate that the lower sedimentary section is no older than Barremian and therefore provides support for the age proposed by the tectonic models.
摘要构造模型表明，在新新时代早期，莫桑比克海脊上没有深水连接。这些模型暗示了在巴雷米亚-最早阿普提时代形成的南大西洋和印度洋之间的深水连接的开始。然而，先前对莫桑比克海脊最早的深水沉积物的生物地层学研究表明，基底部分的年龄为新新纪。在这里，我们提出了一种新的生物地层学分析方法来测试这个构造模型，并确定莫桑比克海岭深水沉积的最早年龄。采集了25 Leg 249号DSDP站点222.05 - 406.32 m白垩纪(19-32)岩心样品，进行了钙质纳米浮游生物和孢粉学分析。大部分采样集中在294 m以下的下白垩统层段。研究结果表明，下沉积剖面比巴雷米亚期更早，因此为构造模型提出的年龄提供了支持。
{"title":"Micropalaeontological dating of the basal Cretaceous section of DSDP Site 249, Leg 25, Mozambique Ridge: implications for the timing of the southern Atlantic–Indian Ocean connection","authors":"R. Dunay, W. Braham, M. K. E. Cooper, Martin Lester, F. Tremolada","doi":"10.5194/JM-37-305-2018","DOIUrl":"https://doi.org/10.5194/JM-37-305-2018","url":null,"abstract":"Abstract. Tectonic models suggest the absence of a deep water connection on the\u0000Mozambique Ridge during early Neocomian time. These models imply the\u0000initiation of a deep water connection between the southern Atlantic and\u0000Indian oceans formed during Barremian–earliest Aptian times. However,\u0000previous biostratigraphic studies of the earliest deep water sediments on the\u0000Mozambique Ridge suggest that the basal section is Neocomian in age. Here, we\u0000present a new biostratigraphic analysis undertaken to test this tectonic\u0000model and determine the earliest age of deep water sedimentation on the\u0000Mozambique Ridge. Core samples from the Cretaceous interval\u0000222.05–406.32 m (Cores 19–32) of DSDP Site 249, Leg 25, were\u0000sampled for calcareous nannoplankton and palynological analysis. Most of the\u0000sampling was concentrated on the Lower Cretaceous interval below\u0000294 m . Our results indicate that the lower sedimentary section is no\u0000older than Barremian and therefore provides support for the age proposed by\u0000the tectonic models.","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2018-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46097777","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Hemisphaerammina apta n. sp. is an attached monothalamous agglutinated foraminifera discovered in shelf sediments of the early Eocene Arctic Ocean. It is a simple yet distinctive component of the endemic agglutinated foraminiferal assemblage that colonized the Arctic Ocean after the microfaunal turnover caused by the Paleocene–Eocene Thermal Maximum. Associated foraminifera are characterized by a high percentage of monothalamous species (up to 60 %) and are entirely agglutinated indicating a brackish (mesohaline) early Eocene Arctic Ocean. Hemisphaerammina apta occurs exclusively as individuals attached to fine detrital grains (0.2 to 1.8 mm) of sediment. It is a small species (0.06 to 0.2 mm in diameter), fine-grained, with a low hemispherical profile, no floor across the attachment area, no substantive marginal flange, no internal structures, and no aperture. Lacking an aperture, it apparently propagated and fed through minute (micrometre-sized) interstitial pores in the test wall. Attachment surfaces vary from concave to convex and rough to smooth. Grains for attachment are diverse in shape and type but are predominantly of quartz and chert. The presence of H. apta in the early Eocene was an opportunistic response to an environment with an active hydrological system (storm events). Attachment to grains of sand would provide a more stable base on a sea floor winnowed by storm-generated currents. Active transport is indicated by the relative abundance of reworked foraminifera mixed with in situ species. Contemporaneous reworking and colonization by H. apta is suggested by its attachment to a reworked specimen of Cretaceous foraminifera.
{"title":"On a grain of sand – a microhabitat for the opportunistic agglutinated foraminifera Hemisphaerammina apta n. sp., from the early Eocene Arctic Ocean","authors":"D. McNeil, L. Neville","doi":"10.5194/JM-37-295-2018","DOIUrl":"https://doi.org/10.5194/JM-37-295-2018","url":null,"abstract":"Abstract. Hemisphaerammina apta n. sp. is an attached monothalamous agglutinated foraminifera discovered in shelf sediments of the early Eocene Arctic Ocean. It is a simple yet distinctive component of the endemic agglutinated foraminiferal assemblage that colonized the Arctic Ocean after the microfaunal turnover caused by the Paleocene–Eocene Thermal Maximum. Associated foraminifera are characterized by a high percentage of monothalamous species (up to 60 %) and are entirely agglutinated indicating a brackish (mesohaline) early Eocene Arctic Ocean. Hemisphaerammina apta occurs exclusively as individuals attached to fine detrital grains (0.2 to 1.8 mm) of sediment. It is a small species (0.06 to 0.2 mm in diameter), fine-grained, with a low hemispherical profile, no floor across the attachment area, no substantive marginal flange, no internal structures, and no aperture. Lacking an aperture, it apparently propagated and fed through minute (micrometre-sized) interstitial pores in the test wall. Attachment surfaces vary from concave to convex and rough to smooth. Grains for attachment are diverse in shape and type but are predominantly of quartz and chert. The presence of H. apta in the early Eocene was an opportunistic response to an environment with an active hydrological system (storm events). Attachment to grains of sand would provide a more stable base on a sea floor winnowed by storm-generated currents. Active transport is indicated by the relative abundance of reworked foraminifera mixed with in situ species. Contemporaneous reworking and colonization by H. apta is suggested by its attachment to a reworked specimen of Cretaceous foraminifera.","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2018-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48310618","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. A two-dimensional morphometric programme, recently designed to measure fossil skeletons of the silicoflagellate genus Corbisema, was used to investigate specimens of the C. apiculata–C. triacantha complex found in a sample from the Fur Formation on the island of Mors, Jutland, Denmark. The semi-automated programme measured the lengths of the basal sides and radial spines, the basal side curvature, and the location of the pikes (if present) from a photographic database ( N=469 ). As a result, two distinct morphological groups were revealed based on their radial spine length : basal side length ratio and the presence or absence of pikes: group A (ratio of 1 : 1.3, no pikes) and group B, with the latter subdivided into B1 (ratio of 1 : 7, with pikes) and B2 (ratio of 1 : 6, no pikes). Group A (C. triacantha sensu lato) possesses a small basal ring with relatively straight basal sides and long radial spines, while group B has a large basal ring with curved basal sides and short radial spines. In B1 specimens (C. apiculata sensu stricto) the pikes are positioned 0 to 1 µ m away from the junction point of the strut and basal ring. This would suggest that B1 double skeletons are likely to be in the Star-of-David configuration, while A and B2 double skeletons (which lack pikes) are likely to be in the corner-to-corner configuration. Compared with the previously published biometric studies of extant Stephanocha (Stephanocha speculum complex in the Southern Ocean and S. medianoctisol in the Arctic Ocean), the results are somewhat different: although C. triacantha sensu lato (group A) is similar to the modern species of Stephanocha, the latter have smaller basal ring diameters, whereas specimens of C. apiculata sensu lato (types B1 and B2) have large basal rings. If their cell diameters are calculated, B1 is the largest, with S. speculum being the smallest – about half the size of B1. This could suggest that the relationship between radial spine length and mean basal ring size has shifted over geological time.
摘要最近设计的一个二维形态测量程序用于测量硅鞭藻属Corbisema的化石骨骼，该程序被用于调查尖花C.apiculata–C。在丹麦日德兰群岛莫尔斯岛富尔组的样本中发现的三角珊瑚复合体。该半自动化程序从照片数据库中测量了基底侧和桡侧棘的长度、基底侧曲率和尖刺的位置（如果存在）（N=469）。结果，根据它们的径向自旋长度，发现了两个不同的形态组 : 基础边长比和是否有尖刺：A组（比率为1 : 1.3，无毛刺）和B组，后者细分为B1（比率为1 : 7，带尖头）和B2（比例为1 : 6，没有长矛）。A组（C.triacantha sensu lato）有一个小的基环，具有相对直的基侧和长的径向棘，而B组有一个基环，基侧弯曲，短的径向棘。在B1标本（C.apiculata sense stricto）中，矛的位置为0到1 距离支柱和基础环的连接点µm。这表明B1双骨骼很可能处于大卫之星构型，而A和B2双骨骼（缺乏长矛）很可能处于角对角构型。与先前发表的对现存Stephanocha（南大洋的Stephanocha-spectrum复合体和北冰洋的S.medianoctisol）的生物特征研究相比，结果有些不同：尽管C.triacantha sensu lato（A组）与现代物种Stephanoch相似，但后者的基环直径较小，而刺桐标本（B1型和B2型）具有较大的基环。如果计算它们的细胞直径，B1是最大的，窥器梭是最小的——大约是B1的一半大小。这可能表明径向自旋长度和平均基底环尺寸之间的关系随着地质时间的推移而发生了变化。
{"title":"Morphometric analysis of early Eocene Corbisema skeletons (Silicoflagellata) in Mors, Denmark","authors":"H. Tsutsui, R. Jordan, N. Nishiwaki, S. Nishida","doi":"10.5194/JM-37-283-2018","DOIUrl":"https://doi.org/10.5194/JM-37-283-2018","url":null,"abstract":"Abstract. A two-dimensional morphometric programme, recently designed to measure fossil\u0000skeletons of the silicoflagellate genus Corbisema, was used to\u0000investigate specimens of the C. apiculata–C. triacantha\u0000complex found in a sample from the Fur Formation on the island of Mors,\u0000Jutland, Denmark. The semi-automated programme measured the lengths of the\u0000basal sides and radial spines, the basal side curvature, and the location of\u0000the pikes (if present) from a photographic database ( N=469 ). As a result,\u0000two distinct morphological groups were revealed based on their radial spine\u0000length : basal side length ratio and the presence or absence of pikes: group A\u0000(ratio of 1 : 1.3, no pikes) and group B, with the latter subdivided into\u0000B1 (ratio of 1 : 7, with pikes) and B2 (ratio of 1 : 6, no pikes).\u0000Group A (C. triacantha sensu lato) possesses a small basal ring with\u0000relatively straight basal sides and long radial spines, while group B has a\u0000large basal ring with curved basal sides and short radial spines. In B1\u0000specimens (C. apiculata sensu stricto) the pikes are positioned 0 to\u00001 µ m away from the junction point of the strut and basal ring. This\u0000would suggest that B1 double skeletons are likely to be in the Star-of-David\u0000configuration, while A and B2 double skeletons (which lack pikes) are likely\u0000to be in the corner-to-corner configuration. Compared with the previously\u0000published biometric studies of extant Stephanocha\u0000(Stephanocha speculum complex in the Southern Ocean and S. medianoctisol in the Arctic Ocean), the results are somewhat different:\u0000although C. triacantha sensu lato (group A) is similar to the modern\u0000species of Stephanocha, the latter have smaller basal ring\u0000diameters, whereas specimens of C. apiculata sensu lato (types B1\u0000and B2) have large basal rings. If their cell diameters are calculated, B1 is\u0000the largest, with S. speculum being the smallest – about half the\u0000size of B1. This could suggest that the relationship between radial spine\u0000length and mean basal ring size has shifted over geological time.","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2018-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45026841","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. The extraction and concentration of biomineralized components from sediment or living materials is time consuming and laborious and often involves steps that remove either the calcareous or siliceous part, in addition to organic matter. However, a relatively quick and easy method using a commercial cleaning fluid for kitchen drains, sometimes combined with a kerosene soaking step, can produce remarkable results. In this study, the method is applied to sediments and living materials bearing calcareous (e.g., coccoliths, foraminiferal tests, holothurian ossicles, ichthyoliths, and fish otoliths) and siliceous (e.g., diatom valves, silicoflagellate skeletons, and sponge spicules) components. The method preserves both components in the same sample, without etching or partial dissolution, but is not applicable to unmineralized components such as dinoflagellate thecae, tintinnid loricae, pollen, or plant fragments.
{"title":"Modified cleaning method for biomineralized components","authors":"H. Tsutsui, R. Jordan","doi":"10.5194/JM-37-249-2018","DOIUrl":"https://doi.org/10.5194/JM-37-249-2018","url":null,"abstract":"Abstract. The extraction and concentration of biomineralized components from sediment\u0000or living materials is time consuming and laborious and often involves steps\u0000that remove either the calcareous or siliceous part, in addition to organic\u0000matter. However, a relatively quick and easy method using a commercial\u0000cleaning fluid for kitchen drains, sometimes combined with a kerosene soaking\u0000step, can produce remarkable results. In this study, the method is applied to\u0000sediments and living materials bearing calcareous (e.g., coccoliths,\u0000foraminiferal tests, holothurian ossicles, ichthyoliths, and fish otoliths)\u0000and siliceous (e.g., diatom valves, silicoflagellate skeletons, and sponge\u0000spicules) components. The method preserves both components in the same\u0000sample, without etching or partial dissolution, but is not applicable to\u0000unmineralized components such as dinoflagellate thecae, tintinnid loricae,\u0000pollen, or plant fragments.","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2018-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45278917","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Junjun Song, Junjun Song, Junjun Song, S. Crasquin, Y. Gong
Abstract. Forty-eight ostracod species belonging to 28 genera from the Late Devonian of Guangxi in South China are described and figured. The ostracod assemblage from the Nandong section can be attributed to the rhenana–linguiformis conodont zones. The ecological assemblages of ostracods from the Yangdi section correspond to a smooth-podocopid association accompanied by some pelagic entomozoids. This mixed assemblage is indicative of an environment of carbonate platform to slope during an ongoing regression. The ostracod faunas from the Nandong section are on the contrary composed of both pelagic and benthic ostracods and pelagic forms dominate in number of specimens suggesting a basin environment.
{"title":"Ostracods (Crustacea) as shelf to basin indicators: evidence from Late Devonian Yangdi and Nandong sections in Guangxi, South China","authors":"Junjun Song, Junjun Song, Junjun Song, S. Crasquin, Y. Gong","doi":"10.5194/JM-37-257-2018","DOIUrl":"https://doi.org/10.5194/JM-37-257-2018","url":null,"abstract":"Abstract. Forty-eight ostracod species belonging to 28 genera from the Late Devonian of\u0000Guangxi in South China are described and figured. The ostracod assemblage\u0000from the Nandong section can be attributed to the\u0000rhenana–linguiformis conodont zones. The ecological assemblages of\u0000ostracods from the Yangdi section correspond to a smooth-podocopid\u0000association accompanied by some pelagic entomozoids. This mixed assemblage is\u0000indicative of an environment of carbonate platform to slope during an ongoing\u0000regression. The ostracod faunas from the Nandong section are on the contrary\u0000composed of both pelagic and benthic ostracods and pelagic forms dominate in\u0000number of specimens suggesting a basin environment.","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2018-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48495653","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. This paper documents a warming event across the middle–upper Albian interval in a ∼ 22 m long section from the Gault Clay Formation of Copt Point, Folkestone (UK). Evidence for the event comes from three independent datasets: calcareous nannofossils, ammonites, and the bulk sediment carbon and oxygen stable isotope record, which collectively indicate a brief period ( ∼ 500 kyr) of significant surface water warming (in excess of 6 ∘ C) at around 107.5 Ma (the base of the Dipoloceras cristatum Ammonite Zone). A surface water productivity increase based on high percentages of the eutrophic nannofossil Zeugrhabdotus noeliae is found to be concomitant with this warming event, suggesting that surface waters were nutrient-rich and the warming was associated with increased precipitation and run-off, delivering more nutrients into the basin.
{"title":"A brief warming event in the late Albian: evidence from calcareous nannofossils, macrofossils, and isotope geochemistry of the Gault Clay Formation, Folkestone, southeastern England","authors":"S. Kanungo, P. Bown, J. Young, A. Gale","doi":"10.5194/JM-37-231-2018","DOIUrl":"https://doi.org/10.5194/JM-37-231-2018","url":null,"abstract":"Abstract. This\u0000paper documents a warming event across the middle–upper Albian interval in a\u0000 ∼ 22 m long section from the Gault Clay Formation of Copt Point,\u0000Folkestone (UK). Evidence for the event comes from three independent\u0000datasets: calcareous nannofossils, ammonites, and the bulk sediment carbon\u0000and oxygen stable isotope record, which collectively indicate a brief period\u0000( ∼ 500 kyr) of significant surface water warming (in excess of\u00006 ∘ C) at around 107.5 Ma (the base of the Dipoloceras cristatum Ammonite Zone). A surface water productivity increase based on\u0000high percentages of the eutrophic nannofossil Zeugrhabdotus noeliae\u0000is found to be concomitant with this warming event, suggesting that surface\u0000waters were nutrient-rich and the warming was associated with increased\u0000precipitation and run-off, delivering more nutrients into the basin.","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2018-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41938891","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Integrated analyses of multiple groups of microfossils are frequently performed to unravel the palaeoenvironmental evolution of subsurface coastal successions, where the complex interaction among several palaeoecological factors can be detected with benthic assemblages. This work investigates the palaeoenvironmental resolution potential provided by benthic foraminifera and ostracoda within a Pleistocene lagoonal succession of the Romagna coastal plain (northern Italy). Quantitative approaches and statistical techniques have been applied to both groups in order to understand the main factors that controlled the composition of assemblages and compare the palaeoecological record provided by single fossil groups. The two faunal groups are characterized by the high dominance of opportunistic species (Ammonia tepida–Ammonia parkinsoniana and Cyprideis torosa); however, detailed palaeoecological information is inferred from less common taxa. Benthic foraminiferal assemblages are mainly determined by the frequencies of abnormal individuals and species related to high concentrations of organic matter, showing two assemblages: a stressed assemblage, consistent with a brackish-water environment subject to salinity and oxygen fluctuations, and an unstressed assemblage, which indicates more stable conditions. Despite the lower number of species, ostracoda show more significant differences in terms of species composition and ecological structure between their three assemblages, formed in response to a salinity gradient and indicative of inner, central, and outer lagoon conditions. The stratigraphic distribution of ostracod assemblages shows a general transgressive–regressive trend with minor fluctuations, whereas benthic foraminifera highlight the presence of a significant palaeoenvironmental stress. In this case, the higher abundance along the stratigraphic succession, the higher differentiation of the assemblages, and the well-defined relationship between taxa and ecological parameters determine Ostracoda as the most reliable fossil group for precise palaeoenvironmental reconstructions. Nevertheless, benthic foraminifera indicate palaeoenvironmental stress and can be used to refine the environmental interpretation in the presence of monospecific ostracod assemblages.
{"title":"Benthic foraminifera or Ostracoda? Comparing the accuracy of palaeoenvironmental indicators from a Pleistocene lagoon of the Romagna coastal plain (Italy)","authors":"G. Barbieri, S. Vaiani","doi":"10.5194/JM-37-203-2018","DOIUrl":"https://doi.org/10.5194/JM-37-203-2018","url":null,"abstract":"Abstract. Integrated analyses of multiple groups of microfossils are frequently performed to unravel the palaeoenvironmental evolution of subsurface coastal successions, where the complex interaction among several palaeoecological factors can be detected with benthic assemblages. This work investigates the palaeoenvironmental resolution potential provided by benthic foraminifera and ostracoda within a Pleistocene lagoonal succession of the Romagna coastal plain (northern Italy). Quantitative approaches and statistical techniques have been applied to both groups in order to understand the main factors that controlled the composition of assemblages and compare the palaeoecological record provided by single fossil groups. The two faunal groups are characterized by the high dominance of opportunistic species (Ammonia tepida–Ammonia parkinsoniana and Cyprideis torosa); however, detailed palaeoecological information is inferred from less common taxa. Benthic foraminiferal assemblages are mainly determined by the frequencies of abnormal individuals and species related to high concentrations of organic matter, showing two assemblages: a stressed assemblage, consistent with a brackish-water environment subject to salinity and oxygen fluctuations, and an unstressed assemblage, which indicates more stable conditions. Despite the lower number of species, ostracoda show more significant differences in terms of species composition and ecological structure between their three assemblages, formed in response to a salinity gradient and indicative of inner, central, and outer lagoon conditions. The stratigraphic distribution of ostracod assemblages shows a general transgressive–regressive trend with minor fluctuations, whereas benthic foraminifera highlight the presence of a significant palaeoenvironmental stress. In this case, the higher abundance along the stratigraphic succession, the higher differentiation of the assemblages, and the well-defined relationship between taxa and ecological parameters determine Ostracoda as the most reliable fossil group for precise palaeoenvironmental reconstructions. Nevertheless, benthic foraminifera indicate palaeoenvironmental stress and can be used to refine the environmental interpretation in the presence of monospecific ostracod assemblages.","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2018-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48706463","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Two new species of bairdiid Ostracoda are described from the lower Barremian – Hauterivian interval of the Valhall and Asgard formations in the northern and central North Sea and Atlantic margin off Norway. The new species are Pontocyprella valhalla (lsid:zoobank.org:act:CA6B273F-CFF6-4C38-B9F4-18188225A711, 18 January 2018) and Bairdia asgarda (lsid:zoobank.org:act:4A4DC817-A028-45FB-9287-ABF3794F2FCB, 18 January 2018). These species dominate the ostracod assemblage that occurs abundantly in early Barremian–Hauterivian deep marine sediments of the northern and central North Sea and Haltenbanken area off Norway. Pontocyprella valhalla is restricted to this interval and because of its large size and distinct shape is a useful stratigraphic marker species, its last appearance being within the early Barremian.
{"title":"Two new bairdiid ostracod species from the early Barremian–Hauterivian of the northern and central North Sea to the Atlantic margin off Norway","authors":"M. Ayress, T. Gould","doi":"10.5194/JM-37-195-2018","DOIUrl":"https://doi.org/10.5194/JM-37-195-2018","url":null,"abstract":"Abstract. Two new species of bairdiid Ostracoda are described from the lower Barremian\u0000– Hauterivian interval of the Valhall and Asgard formations in the\u0000northern and central North Sea and Atlantic margin off Norway. The new\u0000species are Pontocyprella valhalla\u0000(lsid:zoobank.org:act:CA6B273F-CFF6-4C38-B9F4-18188225A711, 18 January 2018)\u0000and Bairdia asgarda\u0000(lsid:zoobank.org:act:4A4DC817-A028-45FB-9287-ABF3794F2FCB, 18 January 2018).\u0000These species dominate the ostracod assemblage that occurs abundantly in\u0000early Barremian–Hauterivian deep marine sediments of the northern and\u0000central North Sea and Haltenbanken area off Norway. Pontocyprella valhalla is restricted to this interval and because of its large size and\u0000distinct shape is a useful stratigraphic marker species, its last appearance\u0000being within the early Barremian.","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2018-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44717748","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. The type material of Cylindroporella sugdeni Elliott, 1957, is revised. The total lack of sterile laterals and consequently the absence of the diagnostic feature of the genus Cylindroporella, i.e., the alternation of sterile and fertile laterals within the same whorl, leads to its exclusion from the genus Cylindroporella Johnson, 1954, and to its ascription to the genus Holosporella Pia, 1930. Recent stratigraphic investigations suggest that the stratum typicum originally reported as Early Cretaceous in age is more precisely Hauterivian or possibly Early Barremian in age.
{"title":"Cylindroporella sugdeni Elliott, 1957, an Early Cretaceous Middle Eastern Dasycladalean alga – a revision","authors":"B. Granier","doi":"10.5194/JM-37-181-2018","DOIUrl":"https://doi.org/10.5194/JM-37-181-2018","url":null,"abstract":"Abstract. The type material of Cylindroporella sugdeni Elliott, 1957, is\u0000revised. The total lack of sterile laterals and consequently the absence of\u0000the diagnostic feature of the genus Cylindroporella, i.e., the\u0000alternation of sterile and fertile laterals within the same whorl, leads to\u0000its exclusion from the genus Cylindroporella Johnson, 1954, and to\u0000its ascription to the genus Holosporella Pia, 1930. Recent\u0000stratigraphic investigations suggest that the stratum typicum originally\u0000reported as Early Cretaceous in age is more precisely Hauterivian or possibly\u0000Early Barremian in age.","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2018-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49076567","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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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