L. Consorti, Borhan Bagherpour, Masoumeh Soleimani
In the Upper Cretaceous of the Middle East, rotaliid Foraminifera have conventionally been attributed to Rotalia skourensis Pfender (= Rotorbinella skourensis), a key element of biozones #30 and #31 as commonly recognized in the Iranian Zagros. However, R. skourensis is a Paleocene species and is morphologically distinct from the rotaliid specimens present in the Upper Cretaceous of theMiddle East. Through detailed sampling of the Ilam Formation (Turonian?–Campanian) in the Zagros basin, two new species previously classified as R. skourensis have been described. Rotorbinella pachypila n. sp. andOrbitokathina parva n. sp. contribute to our understanding of the diversity of rotaliids during the Late Cretaceous of the Arabian Plate and highlight biogeographic connections with the western Tethys carbonate platform domains.
在中东地区的上白垩统，有孔虫中的有孔虫通常被认为是伊朗扎格罗斯（Zagros）地区公认的 30 号和 31 号生物区的关键要素--Rotalia skourensis Pfender（= Rotorbinella skourensis）。然而，R. skourensis 是古新世物种，在形态上与中东地区上白垩世的轮虫标本截然不同。通过对扎格罗斯盆地伊拉姆地层（都伦纪-坎帕尼亚纪）的详细取样，描述了两个以前被归类为R. skourensis的新物种。Rotorbinella pachypila n. sp.和Orbitokathina parva n. sp.有助于我们了解阿拉伯板块晚白垩世啮齿目动物的多样性，并突出了与特提斯西部碳酸盐平台域的生物地理联系。
{"title":"Discerning species among the foraminiferal “Rotalia skourensis” morphotypes of the Middle East","authors":"L. Consorti, Borhan Bagherpour, Masoumeh Soleimani","doi":"10.47894/mpal.70.3.05","DOIUrl":"https://doi.org/10.47894/mpal.70.3.05","url":null,"abstract":"In the Upper Cretaceous of the Middle East, rotaliid Foraminifera have conventionally been attributed to Rotalia skourensis Pfender (= Rotorbinella skourensis), a key element of biozones #30 and #31 as commonly recognized in the Iranian Zagros. However, R. skourensis is a Paleocene species and is morphologically distinct from the rotaliid specimens present in the Upper Cretaceous of theMiddle East. Through detailed sampling of the Ilam Formation (Turonian?–Campanian) in the Zagros basin, two new species previously classified as R. skourensis have been described. Rotorbinella pachypila n. sp. andOrbitokathina parva n. sp. contribute to our understanding of the diversity of rotaliids during the Late Cretaceous of the Arabian Plate and highlight biogeographic connections with the western Tethys carbonate platform domains.","PeriodicalId":49816,"journal":{"name":"Micropaleontology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141038729","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}
A new calcareous alga is described from the Norian limestones of Lime Peak, Yukon, Canada. The algae-bearing limestones were formed in a low-energy environment below the storm wave base, as indicated by the abundance of carbonate mud. Clypeina? pamelareidae n. sp. usually appears in the form of separate laterals scattered in the sediment. The laterals are pyriform, with the tip slightly curved upwards. Sometimes they are arranged around a non-calcified axial cavity. The lack of calcification of the connection between the main axis and the laterals led to the detachment and scattering of the latter in the sediment. The shape of the laterals and their arrangement are reminiscent of the genus Clypeina (Michelin). Still, the lack of completely preserved specimens leads us to attribute it with uncertainty to this genus. Almost certainly, the alga in question is individualised as a new distinct species, basically different from other Mesozoic or Cenozoic species of the genus, as well as from the only species of Clypeina known from the Triassic (Clypeina besici Pantic).
{"title":"Clypeina? pamelareidae n. sp., a new dasycladalean alga from the Upper Triassic of Lime Peak (Yukon, Canada)","authors":"I. Bucur, N. Del Piero, Rossana Martini","doi":"10.47894/mpal.70.3.04","DOIUrl":"https://doi.org/10.47894/mpal.70.3.04","url":null,"abstract":"A new calcareous alga is described from the Norian limestones of Lime Peak, Yukon, Canada. The algae-bearing limestones were formed in a low-energy environment below the storm wave base, as indicated by the abundance of carbonate mud. Clypeina? pamelareidae n. sp. usually appears in the form of separate laterals scattered in the sediment. The laterals are pyriform, with the tip slightly curved upwards. Sometimes they are arranged around a non-calcified axial cavity. The lack of calcification of the connection between the main axis and the laterals led to the detachment and scattering of the latter in the sediment. The shape of the laterals and their arrangement are reminiscent of the genus Clypeina (Michelin). Still, the lack of completely preserved specimens leads us to attribute it with uncertainty to this genus. Almost certainly, the alga in question is individualised as a new distinct species, basically different from other Mesozoic or Cenozoic species of the genus, as well as from the only species of Clypeina known from the Triassic (Clypeina besici Pantic).","PeriodicalId":49816,"journal":{"name":"Micropaleontology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141039398","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}
V. Fortiz, Rosie Oakes, F. G. Boudinot, M. M. Jones, R. M. Leckie, A. Parker, Brad Sageman, Julio Sepúlveda, T. Bralower
Oceanic Anoxic Event 2 (OAE2) at the Cenomanian/Turonian Boundary (CTB: 93.9Ma) involved the global deposition of organic carbon-rich sediments, a distinctive positive shift in carbon isotope values, and significant species turnover, including changes in calcareous nannofossil assemblages. While it is thought that volcanism triggered organic C-rich sediment deposition during OAE2, it is unclear whether enhanced productivity, increased stratification, of some combination of the two increased organic matter preservation. Calcareous nannofossil assemblages have the potential to qualitatively assess changes in ocean nutrient and temperature conditions to disentangle such ecological dynamics during OAE2. Here we study an expanded section of the Tropic Shale in a drill core in southern Utah near the western margin of the Western Interior Seaway (WIS) to understand how circulation changed during the event and how this may have influenced primary productivity and organic carbon burial. Relative abundance data of well-preserved nannoplankton are complemented with measurements of trace metal, and organic carbon and carbonate concentrations to determine changes in temperature and water column structure, as well as controls on surface water productivity. Detailed statistical analysis helps refine species paleoecologies combined with information from planktic and benthic foraminiferal assemblages and organic biomarkers. Changes in calcareous nannofossil assemblages indicate that near the start of OAE2 the western WIS surface ocean actually cooled for a short time. Following this, surface waters became warmer and more stratified as a Tethyan water mass invaded the seaway. Assemblages suggest that warmth persisted for much of the OAE2 interval, while stratification waxed and waned. The local seaway cooled near the end of OAE2 as Boreal water masses streamed along the western margin. Variations, including the decrease in the abundance of Biscutum constans and short-lived peaks in the abundance of Eprolithus spp. are super regional or possibly global in extent. There is no correlation between calcareous nannofossil assemblages and trace metal concentrations, suggesting they were unaffected by volcanism-related nutrient inputs. Assemblages support other data that suggest increased stratification influenced organic carbon burial in the Western Interior Seaway, and possibly elsewhere, during OAE2.
{"title":"Paleoceanographic Significance of Calcareous Nannofossil Assemblages in the Tropic Shale of Utah during Oceanic Anoxic Event 2 at the Cenomanian/Turonian Boundary","authors":"V. Fortiz, Rosie Oakes, F. G. Boudinot, M. M. Jones, R. M. Leckie, A. Parker, Brad Sageman, Julio Sepúlveda, T. Bralower","doi":"10.47894/mpal.70.3.01","DOIUrl":"https://doi.org/10.47894/mpal.70.3.01","url":null,"abstract":"Oceanic Anoxic Event 2 (OAE2) at the Cenomanian/Turonian Boundary (CTB: 93.9Ma) involved the global deposition of organic carbon-rich sediments, a distinctive positive shift in carbon isotope values, and significant species turnover, including changes in calcareous nannofossil assemblages. While it is thought that volcanism triggered organic C-rich sediment deposition during OAE2, it is unclear whether enhanced productivity, increased stratification, of some combination of the two increased organic matter preservation. Calcareous nannofossil assemblages have the potential to qualitatively assess changes in ocean nutrient and temperature conditions to disentangle such ecological dynamics during OAE2. Here we study an expanded section of the Tropic Shale in a drill core in southern Utah near the western margin of the Western Interior Seaway (WIS) to understand how circulation changed during the event and how this may have influenced primary productivity and organic carbon burial. Relative abundance data of well-preserved nannoplankton are complemented with measurements of trace metal, and organic carbon and carbonate concentrations to determine changes in temperature and water column structure, as well as controls on surface water productivity. Detailed statistical analysis helps refine species paleoecologies combined with information from planktic and benthic foraminiferal assemblages and organic biomarkers. Changes in calcareous nannofossil assemblages indicate that near the start of OAE2 the western WIS surface ocean actually cooled for a short time. Following this, surface waters became warmer and more stratified as a Tethyan water mass invaded the seaway. Assemblages suggest that warmth persisted for much of the OAE2 interval, while stratification waxed and waned. The local seaway cooled near the end of OAE2 as Boreal water masses streamed along the western margin. Variations, including the decrease in the abundance of Biscutum constans and short-lived peaks in the abundance of Eprolithus spp. are super regional or possibly global in extent. There is no correlation between calcareous nannofossil assemblages and trace metal concentrations, suggesting they were unaffected by volcanism-related nutrient inputs. Assemblages support other data that suggest increased stratification influenced organic carbon burial in the Western Interior Seaway, and possibly elsewhere, during OAE2.","PeriodicalId":49816,"journal":{"name":"Micropaleontology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141047597","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}
Yaroslav S. Trubin, Vladimir A. Marinov, P. V. Smirnov, A. A. Novoselov, Martin R Langer
During the Late Eocene, the West Siberian Basin became increasingly isolated from the Peri-Tethys Ocean. The final stage of this marine connection is marked by sediments of the Tavda Formation thatwere deposited during the Bartonian and Priabonion. We have analyzed the composition, structure and diversity of benthic foraminiferal assemblages in core material from the Kyshtyrla Quarry located in the southwest of Western Siberia to reconstruct the depositional environment during the terminal phase of marine sedimentation in theWest Siberian Basin (Upper Tavda Subformation). The foraminiferal record was jointly used with lithological and geochemical multi-proxy data to infer the chronology of events that shaped the critical transition until the complete closure of the basin. Based on stratigraphic index markers, a Priabonian age is indicated for sediments of the Upper Tavda Subformation. From the bottom to the top of the core, the foraminiferal biotas progressively shift from shallow subtidal to low-diverse and stress-tolerant intertidal assemblages, indicative for an increasing isolation of the West Siberian Basin. The increasing shallowing of the marine basin is accompanied by a gradual shift in grain size, and the continuous presence of benthic foraminifera and ratios of geochemical proxies (Sr/Ba, Si/Al, Ti/Al, Zr/Al, K/Al, and U/Th) indicate that mainly marine to brackish water conditions prevailed.
{"title":"Upper Eocene benthic foraminiferal assemblages from Western Siberia (Trans-Ural Region): a multi-proxy approach to infer environmental changes","authors":"Yaroslav S. Trubin, Vladimir A. Marinov, P. V. Smirnov, A. A. Novoselov, Martin R Langer","doi":"10.47894/mpal.70.3.07","DOIUrl":"https://doi.org/10.47894/mpal.70.3.07","url":null,"abstract":"During the Late Eocene, the West Siberian Basin became increasingly isolated from the Peri-Tethys Ocean. The final stage of this marine connection is marked by sediments of the Tavda Formation thatwere deposited during the Bartonian and Priabonion. We have analyzed the composition, structure and diversity of benthic foraminiferal assemblages in core material from the Kyshtyrla Quarry located in the southwest of Western Siberia to reconstruct the depositional environment during the terminal phase of marine sedimentation in theWest Siberian Basin (Upper Tavda Subformation). The foraminiferal record was jointly used with lithological and geochemical multi-proxy data to infer the chronology of events that shaped the critical transition until the complete closure of the basin. Based on stratigraphic index markers, a Priabonian age is indicated for sediments of the Upper Tavda Subformation. From the bottom to the top of the core, the foraminiferal biotas progressively shift from shallow subtidal to low-diverse and stress-tolerant intertidal assemblages, indicative for an increasing isolation of the West Siberian Basin. The increasing shallowing of the marine basin is accompanied by a gradual shift in grain size, and the continuous presence of benthic foraminifera and ratios of geochemical proxies (Sr/Ba, Si/Al, Ti/Al, Zr/Al, K/Al, and U/Th) indicate that mainly marine to brackish water conditions prevailed.","PeriodicalId":49816,"journal":{"name":"Micropaleontology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141056688","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}
A. K. Bhaumik, Swagata Chaudhuri, Shiv Kumar, Satabdi Mohanty, L. Roy, Amit K. Ghosh, Sarmistha Chowdhury, Tankadhar Behara
The deposition of a substantial amount of clastic sediments in the Krishna Godavari Basin formed a thick layer of nannofossil-rich clay known as the Godavari Clay Formation. This clayey sequence is a treasure trove for unveiling paleoclimatic and paleoceanographic information. Numerous radiometric dates from the topmost portion of this clay (top 27m) are available, covering the last 43 ka. However, the availability of data on age connotation with considerably high resolution for the deeper sediments is rare and is still awaited. In this study, we pursued nannoplankton and planktic foraminiferal investigations on the top 198 m (Hole 10D), 300 m (Hole 3B), and 198 m (Hole 5C) sediments of this basin to generate multiple age data with a relatively high resolution. First Occurrence (FO) and Last Occurrence (LO) of nannoplankton taxa Emiliania huxleyi, Helicosphaera inversa, Helicosphaera sellii, large Gephyrocapsa spp., Pseudoemiliania lacunosa, Reticulofenestra asanoi, and planktic foraminiferal taxa Globorotalia flexuosa and Globigerinella calida are considered as potential index taxa for establishing the bioevents as well as biostratigraphy.Based on these, we have identified nine events from Hole 10D, six events from Hole 3B, and seven events from Hole 5C, which are potential for assigning the relative ages.We also observed two-fold variations in sedimentation rates in all the holes and one hiatus at 110.73 mbsf in Hole 5C, indicating a shift in climate and basinal settings. A high sedimentation rate of greater than 20.59 cm/ka after approximately 0.4 Ma at all the holes is probably linked to the intensification of the Indian summer monsoon across the mid-Brunhes Epoch. The significantly low sedimentation rates (less than 14.62 cm/ka) in older sediment sequences before 0.4Ma is probably related to the relatively weak monsoonal activity. The generated age data, variations in sedimentation rates, and identified hiatus are considered to be potential for delineating paleoclimatic and paleoceanographic changes of this area since the Calabrian Stage.
{"title":"Biostratigraphy and sedimentation rate estimation of Quaternary sediments of the Krishna-Godavari Basin, Bay of Bengal: Evidence from NGHP-01 Holes 10D, 5C and 3B","authors":"A. K. Bhaumik, Swagata Chaudhuri, Shiv Kumar, Satabdi Mohanty, L. Roy, Amit K. Ghosh, Sarmistha Chowdhury, Tankadhar Behara","doi":"10.47894/mpal.70.3.03","DOIUrl":"https://doi.org/10.47894/mpal.70.3.03","url":null,"abstract":"The deposition of a substantial amount of clastic sediments in the Krishna Godavari Basin formed a thick layer of nannofossil-rich clay known as the Godavari Clay Formation. This clayey sequence is a treasure trove for unveiling paleoclimatic and paleoceanographic information. Numerous radiometric dates from the topmost portion of this clay (top 27m) are available, covering the last 43 ka. However, the availability of data on age connotation with considerably high resolution for the deeper sediments is rare and is still awaited. In this study, we pursued nannoplankton and planktic foraminiferal investigations on the top 198 m (Hole 10D), 300 m (Hole 3B), and 198 m (Hole 5C) sediments of this basin to generate multiple age data with a relatively high resolution. First Occurrence (FO) and Last Occurrence (LO) of nannoplankton taxa Emiliania huxleyi, Helicosphaera inversa, Helicosphaera sellii, large Gephyrocapsa spp., Pseudoemiliania lacunosa, Reticulofenestra asanoi, and planktic foraminiferal taxa Globorotalia flexuosa and Globigerinella calida are considered as potential index taxa for establishing the bioevents as well as biostratigraphy.Based on these, we have identified nine events from Hole 10D, six events from Hole 3B, and seven events from Hole 5C, which are potential for assigning the relative ages.We also observed two-fold variations in sedimentation rates in all the holes and one hiatus at 110.73 mbsf in Hole 5C, indicating a shift in climate and basinal settings. A high sedimentation rate of greater than 20.59 cm/ka after approximately 0.4 Ma at all the holes is probably linked to the intensification of the Indian summer monsoon across the mid-Brunhes Epoch. The significantly low sedimentation rates (less than 14.62 cm/ka) in older sediment sequences before 0.4Ma is probably related to the relatively weak monsoonal activity. The generated age data, variations in sedimentation rates, and identified hiatus are considered to be potential for delineating paleoclimatic and paleoceanographic changes of this area since the Calabrian Stage.","PeriodicalId":49816,"journal":{"name":"Micropaleontology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141032784","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}
Mike Kaminski, Asmaa Korin, S. Hikmahtiar, L. Alegret, A. Waśkowska
Deep-water benthic foraminifera are investigated from Paleocene to Eocene sediments recovered from IODP Hole U1511B in the northeastern Tasman Sea. The recovered foraminifera display exceptional three-dimensional preservation: they are relatively unaltered by sediment diagenesis and compaction. We examined 33 samples from Cores U1511B-33R to -42R, and recovered 79 species of deep-water agglutinated foraminifera (DWAF) and 13 species of calcareous benthic foraminifera. The assemblage consists entirely of “cosmopolitan” forms originally described from the Carpathians, Caucasus, Trinidad, and the western Tethys, and other DSDP/ODP sites, implying that there is little or no endemism among deep-water benthic faunas in the semi-isolated Tasman Sea. The Paleocene–Eocene interval is characterized by successive acmes of Spiroplectammina, Trochammina, ammodiscids, and Karrerulina, and therefore bears striking similarity to previously studied sections in the western Tethys and Boreal North Atlantic. The taxonomic turnover among the DWAF is minor across the P/E contact, with only three apparent extinctions and three originations from the uppermost cores of the Paleocene and the lowermost cores of the Eocene. Calcareous benthic foraminifera were not observed in the Eocene samples, possibly a result of the shoaling of the CCD.
{"title":"Paleocene and Eocene deep-water benthic foraminifera at IODP Site U1511, Tasman Sea: Part 2","authors":"Mike Kaminski, Asmaa Korin, S. Hikmahtiar, L. Alegret, A. Waśkowska","doi":"10.47894/mpal.70.3.06","DOIUrl":"https://doi.org/10.47894/mpal.70.3.06","url":null,"abstract":"Deep-water benthic foraminifera are investigated from Paleocene to Eocene sediments recovered from IODP Hole U1511B in the northeastern Tasman Sea. The recovered foraminifera display exceptional three-dimensional preservation: they are relatively unaltered by sediment diagenesis and compaction. We examined 33 samples from Cores U1511B-33R to -42R, and recovered 79 species of deep-water agglutinated foraminifera (DWAF) and 13 species of calcareous benthic foraminifera. The assemblage consists entirely of “cosmopolitan” forms originally described from the Carpathians, Caucasus, Trinidad, and the western Tethys, and other DSDP/ODP sites, implying that there is little or no endemism among deep-water benthic faunas in the semi-isolated Tasman Sea. The Paleocene–Eocene interval is characterized by successive acmes of Spiroplectammina, Trochammina, ammodiscids, and Karrerulina, and therefore bears striking similarity to previously studied sections in the western Tethys and Boreal North Atlantic. The taxonomic turnover among the DWAF is minor across the P/E contact, with only three apparent extinctions and three originations from the uppermost cores of the Paleocene and the lowermost cores of the Eocene. Calcareous benthic foraminifera were not observed in the Eocene samples, possibly a result of the shoaling of the CCD.","PeriodicalId":49816,"journal":{"name":"Micropaleontology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141031440","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The calcareous nannofossil genus Reticulofenestra and its related taxa are called “reticulofenestrids,” and they were one of the major nannofossil groups during the Cenozoic. The reticulofenestrid specimens are composed of two shields, proximal and distal, which are circular or subcircular in shape and consist of tiny calcite plates. Cyclic changes in the size and shape of reticulofenestrid coccoliths have been used to characterize their evolution. The major taxonomic turnover in this group was related to environmental changes during the Cenozoic. From the Oligocene to the Miocene, there were several different types of reticulofenestrids. The primary taxon of reticulofenestrids disappeared during the Oligocene-Miocene boundary, and elliptical species emerged during the early Miocene. However, it is uncertain exactly when and how the change in reticulofenestrids occurred. To understand the evolutionary trends of reticulofenestrids, we conducted biometric analyses from the Oligocene to the Miocene. Detailed observation and measurement of reticulofenestrid coccoliths under a scanning electron microscope revealed a significant size reduction in the group near the Oligocene–Miocene, which corresponds to a period of rapid global cooling. Furthermore, regarding the reticulofenestrid taxa in this study, central structures characterize the Oligocene genus Dictyococcites, and the long axis length of the coccolith outline and central areas can be effective characteristics for distinguishing between theMiocene Cyclicargolithus and Reticulofenestra. These results suggest that morphological differences of reticulofenestrids are expressed not only in the shape and size of the coccolith but also in the size and shape of its central area.
{"title":"Biometric analysis of the calcareous nannofossil group reticulofenestrids from the Oligocene to the Miocene","authors":"Nobuhiro Doi, Koji Kameo","doi":"10.47894/mpal.70.3.02","DOIUrl":"https://doi.org/10.47894/mpal.70.3.02","url":null,"abstract":"The calcareous nannofossil genus Reticulofenestra and its related taxa are called “reticulofenestrids,” and they were one of the major nannofossil groups during the Cenozoic. The reticulofenestrid specimens are composed of two shields, proximal and distal, which are circular or subcircular in shape and consist of tiny calcite plates. Cyclic changes in the size and shape of reticulofenestrid coccoliths have been used to characterize their evolution. The major taxonomic turnover in this group was related to environmental changes during the Cenozoic. From the Oligocene to the Miocene, there were several different types of reticulofenestrids. The primary taxon of reticulofenestrids disappeared during the Oligocene-Miocene boundary, and elliptical species emerged during the early Miocene. However, it is uncertain exactly when and how the change in reticulofenestrids occurred. To understand the evolutionary trends of reticulofenestrids, we conducted biometric analyses from the Oligocene to the Miocene. Detailed observation and measurement of reticulofenestrid coccoliths under a scanning electron microscope revealed a significant size reduction in the group near the Oligocene–Miocene, which corresponds to a period of rapid global cooling. Furthermore, regarding the reticulofenestrid taxa in this study, central structures characterize the Oligocene genus Dictyococcites, and the long axis length of the coccolith outline and central areas can be effective characteristics for distinguishing between theMiocene Cyclicargolithus and Reticulofenestra. These results suggest that morphological differences of reticulofenestrids are expressed not only in the shape and size of the coccolith but also in the size and shape of its central area.","PeriodicalId":49816,"journal":{"name":"Micropaleontology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141031449","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}
Mehdi Hadi, Ali Bahrami, Gyorgy Less, L. Consorti, M. Parandavar
A rich larger foraminifera assemblage from the Eocene carbonates of the south Sabzevar region (Now-Deh section) in central Iran indicates a late Ypresian to early Lutetian age. Nine species of Alveolina d’Orbigny are studied for systematics and biostratigraphy. The assemblage includes A. minuta, A. decastroi, A. cremae, A. cremae elongata, A. decipiens ayrancensis, A. celali, A. rugosa, A. cuspidata, A. frumentiformis. We have also found nummulitids (genus Nummulites and Assilina) and orthophragmines identified as N. campesinus, N. praediscorbinus, A. placentula, A. praespira, A. reicheli, A. ex. intrec. laxispira-maior and Discocyclina archiaci bartholomei. The recovery of Alveolina cremae elongata, A. decipiens ayrancensis, A. celali, A. rugosa, A. cuspidata and Assilina praespira has permitted for the first time to extend their geographical distribution outside of the classical peri-Mediterranean area to the central Tethys regions. The obtained biostratigraphy points to the Shallow Benthic Zones SBZ11 to SBZ13, indicating the occurrence of a Lower–Middle Eocene carbonate system. Part of the age model is supported by the calcareous nannofossil biostratigraphy that belong to the NP14b and CNE8 biozones, recorded from the central portion of the studied section. Issues regarding the application of the SBZ into the Middle East domains are discussed in terms of relative stratigraphic position and biogeographic dispersal of some significant Alveolina species.
{"title":"Biostratigraphy of the Eocene shallow-water succession of the south Sabzevar area (Central Iran) based on larger benthic foraminifera and calcareous nannofossils","authors":"Mehdi Hadi, Ali Bahrami, Gyorgy Less, L. Consorti, M. Parandavar","doi":"10.47894/mpal.70.2.05","DOIUrl":"https://doi.org/10.47894/mpal.70.2.05","url":null,"abstract":"A rich larger foraminifera assemblage from the Eocene carbonates of the south Sabzevar region (Now-Deh section) in central Iran indicates a late Ypresian to early Lutetian age. Nine species of Alveolina d’Orbigny are studied for systematics and biostratigraphy. The assemblage includes A. minuta, A. decastroi, A. cremae, A. cremae elongata, A. decipiens ayrancensis, A. celali, A. rugosa, A. cuspidata, A. frumentiformis. We have also found nummulitids (genus Nummulites and Assilina) and orthophragmines identified as N. campesinus, N. praediscorbinus, A. placentula, A. praespira, A. reicheli, A. ex. intrec. laxispira-maior and Discocyclina archiaci bartholomei. The recovery of Alveolina cremae elongata, A. decipiens ayrancensis, A. celali, A. rugosa, A. cuspidata and Assilina praespira has permitted for the first time to extend their geographical distribution outside of the classical peri-Mediterranean area to the central Tethys regions. The obtained biostratigraphy points to the Shallow Benthic Zones SBZ11 to SBZ13, indicating the occurrence of a Lower–Middle Eocene carbonate system. Part of the age model is supported by the calcareous nannofossil biostratigraphy that belong to the NP14b and CNE8 biozones, recorded from the central portion of the studied section. Issues regarding the application of the SBZ into the Middle East domains are discussed in terms of relative stratigraphic position and biogeographic dispersal of some significant Alveolina species.","PeriodicalId":49816,"journal":{"name":"Micropaleontology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140084442","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}
A small suite of seafloor sediment samples (water depth less than 20 m) was collected in 2005 from the sheltered, logarithmic-spiral Guayaguayare Bay along the SE coast of Trinidad, West Indies. The easternmost shielded part of the bay was then occupied by a meadow of the seagrass Halodule wrightii, the closest seagrass bed to the Boca Grande, the main distributary of the Orinoco Delta. Four foraminiferal taphofacies were distinguished, ascribable to a relict coral reef system: (1) A shallow-water (approx. 5 m) taphofacies dominated by Pararotalia sarmientoi. (2) A back-reef taphofacies (approx. 5 m) with abundant Discorbis rosea, apparently associated with the H. wrightii. (3) A fore-reef taphofacies (water depth approx. 20 m) co-dominated by Amphistegina gibbosa and Quinqueloculina bicostata. (4) A reef-flat (approx. 5 m) taphofacies dominated by Q. bicostata. A ternary plot of specimen wall types (agglutinated, porcellaneous, calcareous hyaline) clearly distinguished Taphofacies 1 from Taphofacies 4, porcellaneous specimens being rare in the former. A similar plot of staining + test abrasion for A. gibbosa indicated that those on Taphofacies 3, assumed to be in situ, were more heavily stained than those elsewhere and were larger. Tiny but pristine, presumably allochthonous A. gibbosa were recovered from Taphofacies 1. Two formae of Asterigerina carinata, both widely illustrated in the literature, are distinguished for the first time and named A. carinata forma conica and A. carinata forma discoida. The bay is currently filled with turbid water. The coral reef system, postdating the early Holocene transgression, would have required clear water, perhaps when the Orinoco Delta had not prograded sufficiently to impact the bay greatly. The known best depth range for the growth of amphisteginids, which are symbiotic with algae, coupled with known Holocene sea level curves for the SE Caribbean, suggest an age of approx. 4000 YBP. Sedimentation in the protected bay has since the development of the reef been limited.
2005 年，在西印度群岛特立尼达岛东南海岸的瓜亚瓜亚雷湾（Guayaguayare Bay）采集了一小部分海底沉积物样本（水深小于 20 米）。海湾最东端的遮蔽部分当时被海草 Halodule wrightii 的草甸所占据，这是距离奥里诺科河三角洲主要支流博卡格兰德河最近的海草床。有孔虫分为四种类型，可归属于珊瑚礁系统：(1) 以 Pararotalia sarmientoi 为主的浅水（约 5 米）类型。(2) 后礁（约 5 米）层状结构，有大量的 Discorbis rosea，显然与 H. wrightii 相关。(3）前礁石层（水深约 20 米），以 Amphistegina gibbosa 和 Quinqueloculina bicostata 为主。(4) 以 Q. bicostata 为主的礁平层（水深约 5 米）。标本壁类型的三元图（凝集的、多孔的、钙质透明的）明显区分了暗礁层 1 和暗礁层 4，多孔标本在前者中很少见。对 A. gibbosa 的染色+测试磨损进行类似的绘制表明，Taphofacies 3 上的标本（假定为原位标本）比其他地方的标本染色更严重，体积也更大。在 1 号土层中发现了微小但原始的 A. gibbosa，推测是同生的。首次区分了文献中广泛介绍的 Asterigerina carinata 的两种形态，并将其命名为 A. carinata forma conica 和 A. carinata forma discoida。海湾目前充满了浑浊的海水。珊瑚礁系统形成于全新世早期的大断裂之后，需要清澈的海水，也许当时奥里诺科河三角洲还没有发展到足以对海湾产生巨大影响的地步。已知的两栖类（与藻类共生）生长的最佳深度范围，加上已知的全新世加勒比海东南部海平面曲线，表明其年龄约为 4000 YBP。自珊瑚礁形成以来，受保护海湾的沉积作用一直很有限。
{"title":"Paleoenvironmental significance of Holocene foraminiferal taphocoenoses in Guayaguayare Bay, Trinidad, West Indies: A coral reef near the Orinoco Delta","authors":"B. Wilson, L. Hayek","doi":"10.47894/mpal.70.2.01","DOIUrl":"https://doi.org/10.47894/mpal.70.2.01","url":null,"abstract":"A small suite of seafloor sediment samples (water depth less than 20 m) was collected in 2005 from the sheltered, logarithmic-spiral Guayaguayare Bay along the SE coast of Trinidad, West Indies. The easternmost shielded part of the bay was then occupied by a meadow of the seagrass Halodule wrightii, the closest seagrass bed to the Boca Grande, the main distributary of the Orinoco Delta. Four foraminiferal taphofacies were distinguished, ascribable to a relict coral reef system: (1) A shallow-water (approx. 5 m) taphofacies dominated by Pararotalia sarmientoi. (2) A back-reef taphofacies (approx. 5 m) with abundant Discorbis rosea, apparently associated with the H. wrightii. (3) A fore-reef taphofacies (water depth approx. 20 m) co-dominated by Amphistegina gibbosa and Quinqueloculina bicostata. (4) A reef-flat (approx. 5 m) taphofacies dominated by Q. bicostata. A ternary plot of specimen wall types (agglutinated, porcellaneous, calcareous hyaline) clearly distinguished Taphofacies 1 from Taphofacies 4, porcellaneous specimens being rare in the former. A similar plot of staining + test abrasion for A. gibbosa indicated that those on Taphofacies 3, assumed to be in situ, were more heavily stained than those elsewhere and were larger. Tiny but pristine, presumably allochthonous A. gibbosa were recovered from Taphofacies 1. Two formae of Asterigerina carinata, both widely illustrated in the literature, are distinguished for the first time and named A. carinata forma conica and A. carinata forma discoida. The bay is currently filled with turbid water. The coral reef system, postdating the early Holocene transgression, would have required clear water, perhaps when the Orinoco Delta had not prograded sufficiently to impact the bay greatly. The known best depth range for the growth of amphisteginids, which are symbiotic with algae, coupled with known Holocene sea level curves for the SE Caribbean, suggest an age of approx. 4000 YBP. Sedimentation in the protected bay has since the development of the reef been limited.","PeriodicalId":49816,"journal":{"name":"Micropaleontology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140085406","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}
Observations in 2022 of intertidal and subtidal foraminiferal faunas at four localities along the central-eastern side of Vancouver Island, British Columbia, Canada, and molecular analyses have documented the first occurrence of the nonindigenous Asian species Ammonia confertitesta Zheng in the northwestern Pacific Ocean. The species was present at three of these localities: Davis Lagoon south of Ladysmith (4% in the lagoon and 49% on the beach) and 0.6% in Nanaimo Harbor. The vector of introduction is thought to be the release of ballast water and associated sediment. These releases probably occurred in the Port of Vancouver, which were then transported by means of the cyclonic circulation across the Strait of Georgia, or from local anchorages close to the sampling sites. The timing of the introduction is impossible to determine because no stratigraphic record is presently available. However, foraminiferal studies in the late 1980s near the Port of Vancouver that recovered calcareous taxa did not report the presence of this species, nor was it found at 33 sites sampled from 1997 to 1999 throughout the Strait of Georgia.
{"title":"First Occurrence of the nonindigenous Asian foraminifera Ammonia confertitesta in the Northeastern Pacific Ocean: Vancouver Island, British Columbia, Canada","authors":"M. McGann, Maria Holzmann","doi":"10.47894/mpal.70.2.02","DOIUrl":"https://doi.org/10.47894/mpal.70.2.02","url":null,"abstract":"Observations in 2022 of intertidal and subtidal foraminiferal faunas at four localities along the central-eastern side of Vancouver Island, British Columbia, Canada, and molecular analyses have documented the first occurrence of the nonindigenous Asian species Ammonia confertitesta Zheng in the northwestern Pacific Ocean. The species was present at three of these localities: Davis Lagoon south of Ladysmith (4% in the lagoon and 49% on the beach) and 0.6% in Nanaimo Harbor. The vector of introduction is thought to be the release of ballast water and associated sediment. These releases probably occurred in the Port of Vancouver, which were then transported by means of the cyclonic circulation across the Strait of Georgia, or from local anchorages close to the sampling sites. The timing of the introduction is impossible to determine because no stratigraphic record is presently available. However, foraminiferal studies in the late 1980s near the Port of Vancouver that recovered calcareous taxa did not report the presence of this species, nor was it found at 33 sites sampled from 1997 to 1999 throughout the Strait of Georgia.","PeriodicalId":49816,"journal":{"name":"Micropaleontology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140092105","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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