Pub Date : 2025-11-19DOI: 10.1016/j.marmicro.2025.102529
Mir Amir Salahi , Sreepat Jain
Studies on bioerosion traces and encrustations on orbitolinid tests are relatively less documented in comparison with other larger benthic foraminifera such as nummulitids and other micro-organisms. Hence, as such, these epibionts are difficult to detect in the fossil record, probably because of less working of bioerosional processes on orbitolinids. We document bioerosion traces and encrustations on the orbitolinid Paleodictyoconus from the upper Barremian rocks of the Sarcheshmeh Formation, Kopet-Dagh Basin (north-eastern Iran). Based on the study of 155 samples, four bioerosion ichnotaxa, Entobia, Trypanites, Oichnus, and Gastrochaenolites, along with encrustations by nubeculariid foraminifera, bryozoans, and a coral, are documented. These assemblages are attributed to the Entobia ichnofacies. Additionally, due to their abundance and larger test size, the orbitolinids attached to the bivalve Pinna were also a preferred substrate to settle for the larvae of smaller benthic foraminifera, as noted herein. Coincident with previous studies, the high percentage of borings and encrustation also alludes to calm waters, low rates of sedimentation, and a protected setting, thus, also favouring larval settlement on orbitolinid tests.
{"title":"Bioerosion traces and encrustations on orbitolinid tests from the upper Barremian (Lower Cretaceous) of Kopet-Dagh Basin, northeastern Iran","authors":"Mir Amir Salahi , Sreepat Jain","doi":"10.1016/j.marmicro.2025.102529","DOIUrl":"10.1016/j.marmicro.2025.102529","url":null,"abstract":"<div><div>Studies on bioerosion traces and encrustations on orbitolinid tests are relatively less documented in comparison with other larger benthic foraminifera such as nummulitids and other micro-organisms. Hence, as such, these epibionts are difficult to detect in the fossil record, probably because of less working of bioerosional processes on orbitolinids. We document bioerosion traces and encrustations on the orbitolinid <em>Paleodictyoconus</em> from the upper Barremian rocks of the Sarcheshmeh Formation, Kopet-Dagh Basin (north-eastern Iran). Based on the study of 155 samples, four bioerosion ichnotaxa, <em>Entobia, Trypanites, Oichnus</em>, and <em>Gastrochaenolites</em>, along with encrustations by nubeculariid foraminifera, bryozoans, and a coral, are documented. These assemblages are attributed to the <em>Entobia</em> ichnofacies. Additionally, due to their abundance and larger test size, the orbitolinids attached to the bivalve <em>Pinna</em> were also a preferred substrate to settle for the larvae of smaller benthic foraminifera, as noted herein. Coincident with previous studies, the high percentage of borings and encrustation also alludes to calm waters, low rates of sedimentation, and a protected setting, thus, also favouring larval settlement on orbitolinid tests.</div></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"201 ","pages":"Article 102529"},"PeriodicalIF":1.6,"publicationDate":"2025-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145578703","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-05DOI: 10.1016/j.marmicro.2025.102526
Tatiana S. Klyuvitkina , Ekaterina A. Novichkova , Elizaveta A. Agafonova , Lubov A. Lozinskaia , Karina S. Iakimova , Alexander G. Matul , Maria P. Chekhovskaya , Rahul Mohan , Anne de Vernal
The marine environmental conditions of the last 2.9 cal ka in the Knipovich Ridge area, Norwegian Sea, were reconstructed using micropaleontological and sedimentological data and quantitative estimations of sea-ice cover, surface and subsurface temperatures and salinity. From 2.9 to 2.2 cal kyr BP, harsh conditions prevailed throughout the entire water column, accompanied by low bottom-current activity, which we associate with the final phase of the Neoglacial cooling. A substantial change in the marine environment towards warming and establishment of modern-like oceanic conditions occurred at 2.2 cal kyr BP simultaneously in surface, subsurface and bottom waters. Dinocyst and diatom data suggest the warmest period in surface waters was recorded at 2.2–1.2 cal kyr BP, followed by a short-lived cooling at 1.0–1.2 cal kyr BP marked by sea ice recurrence. Another major shift in ocean conditions occurred at 0.6 cal kyr BP, corresponding to the onset of the Little Ice Age (LIA) and showing decoupling in surface and subsurface water layers. According to our records, the LIA cooling signal in the Knipovich Ridge area was only evident in the upper water layer, without changes throughout the water column. The regional LIA cooling could be associated with cold surface currents from the Barents Sea shelf flowing into the Norwegian Sea in summer.
利用微古生物学和沉积学资料，以及海冰覆盖、地表和地下温度和盐度的定量估算，重建了挪威海Knipovich Ridge地区最近2.9 cal ka的海洋环境条件。从2.9 - 2.2 cal kyr BP，整个水柱的条件都很恶劣，伴随着低底流活动，我们将其与新冰期冷却的最后阶段联系起来。在2.2 calkyr BP，海面、地下和海底同时发生了海洋环境向变暖方向的实质性变化和类似现代海洋条件的建立。藻囊和硅藻资料表明，地表水最温暖的时期记录在2.2-1.2 cal kyr BP，随后是1.0-1.2 cal kyr BP的短暂降温，标志着海冰的复发。另一次海洋条件的重大转变发生在0.6 cal kyr BP，与小冰期（LIA）的开始相对应，并显示了表层和次表层水层的分离。根据我们的记录，Knipovich Ridge地区的LIA冷却信号仅在上层水层明显，整个水柱没有变化。区域性低气压变冷可能与夏季从巴伦支海陆架流入挪威海的冷表面流有关。
{"title":"Late Holocene paleoceanography of the Knipovich Ridge area (Norwegian Sea) based on micropaleontological data","authors":"Tatiana S. Klyuvitkina , Ekaterina A. Novichkova , Elizaveta A. Agafonova , Lubov A. Lozinskaia , Karina S. Iakimova , Alexander G. Matul , Maria P. Chekhovskaya , Rahul Mohan , Anne de Vernal","doi":"10.1016/j.marmicro.2025.102526","DOIUrl":"10.1016/j.marmicro.2025.102526","url":null,"abstract":"<div><div>The marine environmental conditions of the last 2.9 cal ka in the Knipovich Ridge area, Norwegian Sea, were reconstructed using micropaleontological and sedimentological data and quantitative estimations of sea-ice cover, surface and subsurface temperatures and salinity. From 2.9 to 2.2 cal kyr BP, harsh conditions prevailed throughout the entire water column, accompanied by low bottom-current activity, which we associate with the final phase of the Neoglacial cooling. A substantial change in the marine environment towards warming and establishment of modern-like oceanic conditions occurred at 2.2 cal kyr BP simultaneously in surface, subsurface and bottom waters. Dinocyst and diatom data suggest the warmest period in surface waters was recorded at 2.2–1.2 cal kyr BP, followed by a short-lived cooling at 1.0–1.2 cal kyr BP marked by sea ice recurrence. Another major shift in ocean conditions occurred at 0.6 cal kyr BP, corresponding to the onset of the Little Ice Age (LIA) and showing decoupling in surface and subsurface water layers. According to our records, the LIA cooling signal in the Knipovich Ridge area was only evident in the upper water layer, without changes throughout the water column. The regional LIA cooling could be associated with cold surface currents from the Barents Sea shelf flowing into the Norwegian Sea in summer.</div></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"201 ","pages":"Article 102526"},"PeriodicalIF":1.6,"publicationDate":"2025-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145519549","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 objective of this study is to investigate the seasonal variability of benthic foraminifera and to identify environmental factors influencing the observed faunal changes. Surface sediment sampling, hydrological measurements, and measurements of the pelagic production were carried out along a transect of four stations in Kongsfjorden, Svalbard, European Arctic, in the early spring, summer and autumn of 2008 and in spring 2009. The most dominant species was Nonionellina labradorica. The majority of the observed faunal variability can be explained by seasonal changes in bottom-water temperature together with suspended matter of glacial origin, as well as by the food availability controlled by pelagic production. During spring, when the amount of freshly deposited organic matter onto the fjord bottom was high, the absolute abundance of living benthic foraminifera could increase up to eightfold compared to other seasons. Most of the species occupied the upper 0–1 cm of the sediment column, while N. labradorica and G. auriculata preferred the 1–2 cm interval. Adercotryma glomeratum, E.excavatum f. clavatum, R. scorpiurus and R. arctica seem to migrate to deeper habitats during the low-productive period. This behaviour may be indicative of a survival adaptation during low food-quality seasons when the species choose deeper levels, thus, reducing the risk of competition and predation during periods of low food availability, while also benefiting from better oxygen penetration.
{"title":"Seasonal variations of recent benthic foraminifera in the surface sediments of Kongsfjorden, Svalbard","authors":"Patrycja Jernas , Katrine Husum , Dorthe Klitgaard-Kristensen , Matthias Forwick , Marta Głuchowska , Nalan Koç","doi":"10.1016/j.marmicro.2025.102528","DOIUrl":"10.1016/j.marmicro.2025.102528","url":null,"abstract":"<div><div>The objective of this study is to investigate the seasonal variability of benthic foraminifera and to identify environmental factors influencing the observed faunal changes. Surface sediment sampling, hydrological measurements, and measurements of the pelagic production were carried out along a transect of four stations in Kongsfjorden, Svalbard, European Arctic, in the early spring, summer and autumn of 2008 and in spring 2009. The most dominant species was <em>Nonionellina labradorica</em>. The majority of the observed faunal variability can be explained by seasonal changes in bottom-water temperature together with suspended matter of glacial origin, as well as by the food availability controlled by pelagic production. During spring, when the amount of freshly deposited organic matter onto the fjord bottom was high, the absolute abundance of living benthic foraminifera could increase up to eightfold compared to other seasons. Most of the species occupied the upper 0–1 cm of the sediment column, while <em>N. labradorica</em> and <em>G. auriculata</em> preferred the 1–2 cm interval. <em>Adercotryma glomeratum, E.excavatum f. clavatum, R. scorpiurus</em> and <em>R. arctica</em> seem to migrate to deeper habitats during the low-productive period. This behaviour may be indicative of a survival adaptation during low food-quality seasons when the species choose deeper levels, thus, reducing the risk of competition and predation during periods of low food availability, while also benefiting from better oxygen penetration.</div></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"201 ","pages":"Article 102528"},"PeriodicalIF":1.6,"publicationDate":"2025-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145519687","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-27DOI: 10.1016/j.marmicro.2025.102525
Edna de Jesus Francisco Tungo , Elisabetta Erba , Gerson Fauth , Cinzia Bottini
Morphometric analyses of Eprolithus floralis were conducted in the Eastbourne section (southeast England, UK) to quantify size changes of this nannofossil species across Oceanic Anoxic Event 2 (OAE 2; Cenomanian/Turonian boundary, ∼94 Ma). The total and inner diameters exhibit a reduction of 3 % and 2.4 %, respectively, relative to the overall mean size during OAE 2 with minimum values (∼1 μm smaller) occurring at carbon isotope peak B. A recovery of 8.4 % and 5.7 % in two distinct morphotypes were identified: the rounded morphotype is ca. 0.5 μm smaller than the spiky one and starts to be more abundant just prior to OAE 2. The spiky morphotype accounts for 61 % before and 56 % after OAE 2 where it also shows largest average sizes and the smallest diaphragm. Morphometric shifts coincide with the onset of intense volcanism from the Caribbean Plateau whereas the size increase parallels the decline in volcanic activity, suggesting a possible link between environmental recovery and morphological diversification.
Size and abundance minima of E. floralis and Biscutum constans at peak B suggest a shared physiological response, likely reduced calcification, to maximum environmental stress and possibly ocean acidification. However, E. floralis shows earlier size recovery, indicating higher ecological tolerance. No clear correlation is found with the Plenus Cold Event, excluding temperature as a primary control of E. floralis abundance and size.
{"title":"Size variation of Eprolithus floralis across Oceanic Anoxic Event 2 (Late Cretaceous) in the Eastbourne section","authors":"Edna de Jesus Francisco Tungo , Elisabetta Erba , Gerson Fauth , Cinzia Bottini","doi":"10.1016/j.marmicro.2025.102525","DOIUrl":"10.1016/j.marmicro.2025.102525","url":null,"abstract":"<div><div>Morphometric analyses of <em>Eprolithus floralis</em> were conducted in the Eastbourne section (southeast England, UK) to quantify size changes of this nannofossil species across Oceanic Anoxic Event 2 (OAE 2; Cenomanian/Turonian boundary, ∼94 Ma). The total and inner diameters exhibit a reduction of 3 % and 2.4 %, respectively, relative to the overall mean size during OAE 2 with minimum values (∼1 μm smaller) occurring at carbon isotope peak B. A recovery of 8.4 % and 5.7 % in two distinct morphotypes were identified: the <em>rounded</em> morphotype is ca. 0.5 μm smaller than the <em>spiky</em> one and starts to be more abundant just prior to OAE 2. The <em>spiky</em> morphotype accounts for 61 % before and 56 % after OAE 2 where it also shows largest average sizes and the smallest diaphragm. Morphometric shifts coincide with the onset of intense volcanism from the Caribbean Plateau whereas the size increase parallels the decline in volcanic activity, suggesting a possible link between environmental recovery and morphological diversification.</div><div>Size and abundance minima of <em>E. floralis</em> and <em>Biscutum constans</em> at peak B suggest a shared physiological response, likely reduced calcification, to maximum environmental stress and possibly ocean acidification. However, <em>E. floralis</em> shows earlier size recovery, indicating higher ecological tolerance. No clear correlation is found with the Plenus Cold Event, excluding temperature as a primary control of <em>E. floralis</em> abundance and size.</div></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"201 ","pages":"Article 102525"},"PeriodicalIF":1.6,"publicationDate":"2025-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145416871","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-24DOI: 10.1016/j.marmicro.2025.102523
Han Yan , Hanting Zhong , Chenyu Wang , Zongqi Lin , Cai Wang , Xiachao Huang , Chao Chen , Mingcai Hou
Siliceous rocks from the Daba section, Kangmar area (southern Xizang), yield well-preserved radiolarian assemblages that provide new evidence for constraining the stratigraphic age and depositional setting of the northern Neo-Tethys Ocean. The faunas are dominated by Austral Realm taxa such as Fusitanella, Praewindalia, and Archaeotanella, in close affinity with Early Cretaceous assemblages from the Argo Abyssal Plain (ODP Site 765C). Key index species (Hemicryptocapsa regularis, H. exgyrum, Archaeodictyomitra brouweri) indicate Berriasian–Valanginian and late Barremian–early Aptian ages, thereby revising earlier assignments of these rocks to the Late Cretaceous. Geochemical data (MnO/TiO2 ratios of 0.19–0.38; Al/(Al + Fe + Mn) values of 0.51–0.58; REE patterns with slight LREE enrichment, weak negative Ce anomaly, and negative Eu anomaly) point to a continental-margin depositional environment. These results not only resolve long-standing age uncertainties but also highlight the significance of Austral radiolarian distribution for reconstructing Early Cretaceous ocean circulation and paleogeography of the Neo-Tethys.
西藏康玛地区大坝剖面的硅质岩显示了保存完好的放射虫组合，为限定新特提斯洋北部的地层年龄和沉积背景提供了新的证据。动物群以Austral Realm类群Fusitanella、Praewindalia和Archaeotanella为主，与Argo深海平原（ODP Site 765C）早白垩世的组合关系密切。关键指标种（Hemicryptocapsa regularis， H. exgyrum, Archaeodictyomitra broweri）显示了berriasia - valanginian和barremian - Aptian早期，从而修正了早期对这些岩石的晚白垩世定位。地球化学数据(MnO/TiO2比值为0.19 ~ 0.38,Al/(Al + Fe + Mn)值为0.51 ~ 0.58；弱LREE富集、弱Ce负异常、弱Eu负异常的稀土模式指向大陆边缘沉积环境。这些结果不仅解决了长期存在的年龄不确定性，而且突出了南放射虫分布对重建早白垩世海洋环流和新特提斯古地理的意义。
{"title":"Early Cretaceous radiolarians and siliceous rock geochemistry from Kangmar, Southern Xizang: Biostratigraphic, paleoenvironmental, and paleogeographic implications for the Neo-Tethys Ocean","authors":"Han Yan , Hanting Zhong , Chenyu Wang , Zongqi Lin , Cai Wang , Xiachao Huang , Chao Chen , Mingcai Hou","doi":"10.1016/j.marmicro.2025.102523","DOIUrl":"10.1016/j.marmicro.2025.102523","url":null,"abstract":"<div><div>Siliceous rocks from the Daba section, Kangmar area (southern Xizang), yield well-preserved radiolarian assemblages that provide new evidence for constraining the stratigraphic age and depositional setting of the northern Neo-Tethys Ocean. The faunas are dominated by Austral Realm taxa such as <em>Fusitanella</em>, <em>Praewindalia</em>, and <em>Archaeotanella</em>, in close affinity with Early Cretaceous assemblages from the Argo Abyssal Plain (ODP Site 765C). Key index species (<em>Hemicryptocapsa regularis</em>, <em>H. exgyrum</em>, <em>Archaeodictyomitra brouweri</em>) indicate Berriasian–Valanginian and late Barremian–early Aptian ages, thereby revising earlier assignments of these rocks to the Late Cretaceous. Geochemical data (MnO/TiO<sub>2</sub> ratios of 0.19–0.38; Al/(Al + Fe + Mn) values of 0.51–0.58; REE patterns with slight LREE enrichment, weak negative Ce anomaly, and negative Eu anomaly) point to a continental-margin depositional environment. These results not only resolve long-standing age uncertainties but also highlight the significance of Austral radiolarian distribution for reconstructing Early Cretaceous ocean circulation and paleogeography of the Neo-Tethys.</div></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"201 ","pages":"Article 102523"},"PeriodicalIF":1.6,"publicationDate":"2025-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145416872","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}
Foraminiferal assemblages of littoral and coastal environment have been widely used in modern analog studies to interpret the effects of past warm periods, such as those during the Quaternary, on shoreline dynamics and relative sea-level changes. This study analyzes benthic foraminiferal assemblages in four sectors of Bahía Samborombón (R36, RS, C15, and PR), to characterize depositional environments and describe the composition and distribution of benthic foraminiferal assemblage. The comparison between living and total foraminiferal assemblages in Bahía Samborombón reveals that living faunas reflect short-term local conditions, whereas total assemblages provide a more diverse, time-averaged record influenced by depositional and preservational processes. Six species associations characteristic of different marginal-marine depositional environments were identified. Association A, dominated by Cribroelphidium spp., was associated with low salinity, high energy, and a high sand content. Association B, was represented by Trochammina inflata and Jadammina polystoma, typical of mid-marsh environments. Association C, dominated by Astrononion sp.1 and Arenoparella mexicana, was linked to low-salinity tidal channels. Association D, dominated by Jadammina polystoma and Miliammina fusca, represents high marshes. Association E, under greater marine influence, was dominated by Buccella peruviana and Quinqueloculina spp., while association F, dominated by Ammonia parkinsoniana, was related with low marshes to intertidal zones. The results suggest that benthic foraminiferal assemblages primarily respond to variations in conductivity, but they are also influenced by other physicochemical and oceanographic factors, such as tidal regimes, as well as by taphonomic and ecological processes that influencing their distribution and preservation in these marginal-marine environments.
{"title":"Modern benthic foraminifera distribution in littoral environments of Bahía Samborombón","authors":"Angélica Ballesteros-Prada , Emiliana Bernasconi , Isabel Vilanova , Mariel Luengo , Enrique Fucks","doi":"10.1016/j.marmicro.2025.102524","DOIUrl":"10.1016/j.marmicro.2025.102524","url":null,"abstract":"<div><div>Foraminiferal assemblages of littoral and coastal environment have been widely used in modern analog studies to interpret the effects of past warm periods, such as those during the Quaternary, on shoreline dynamics and relative sea-level changes. This study analyzes benthic foraminiferal assemblages in four sectors of Bahía Samborombón (R36, RS, C15, and PR), to characterize depositional environments and describe the composition and distribution of benthic foraminiferal assemblage. The comparison between living and total foraminiferal assemblages in Bahía Samborombón reveals that living faunas reflect short-term local conditions, whereas total assemblages provide a more diverse, time-averaged record influenced by depositional and preservational processes. Six species associations characteristic of different marginal-marine depositional environments were identified. Association A, dominated by <em>Cribroelphidium</em> spp., was associated with low salinity, high energy, and a high sand content. Association B, was represented by <em>Trochammina inflata</em> and <em>Jadammina polystoma</em>, typical of mid-marsh environments. Association C, dominated by <em>Astrononion</em> sp.1 and <em>Arenoparella mexicana</em>, was linked to low-salinity tidal channels. Association D, dominated by <em>Jadammina polystoma</em> and <em>Miliammina fusca</em>, represents high marshes. Association E, under greater marine influence, was dominated by <em>Buccella peruviana</em> and <em>Quinqueloculina</em> spp., while association F, dominated by <em>Ammonia parkinsoniana</em>, was related with low marshes to intertidal zones. The results suggest that benthic foraminiferal assemblages primarily respond to variations in conductivity, but they are also influenced by other physicochemical and oceanographic factors, such as tidal regimes, as well as by taphonomic and ecological processes that influencing their distribution and preservation in these marginal-marine environments.</div></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"201 ","pages":"Article 102524"},"PeriodicalIF":1.6,"publicationDate":"2025-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145362616","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-10DOI: 10.1016/j.marmicro.2025.102520
Bradley Paine , Linda Armbrecht , Christopher Bolch , Gustaaf M. Hallegraeff
Over the past fifty years, Eastern Tasmanian waters have experienced rapid warming, primarily due to the extension of the East Australian Current. This has driven expansion of warm-water biota and decline of those adapted to cooler conditions, including phytoplankton. Presently, plankton monitoring, including diatoms along Eastern Tasmania, spans <100 years. This study reconstructed diatom communities throughout a sediment core spanning 9000 years before present (9 kyrs BP), using microfossil analysis and molecular techniques, including sedimentary ancient DNA (sedaDNA) and 18S rRNA from a 10-year water column archive at the Maria Island IMOS National Reference Station mooring.
Microfossil analysis revealed a dominance of strongly silicified benthic taxa (Campylodiscus, Diploneis, Paralia, Pyxidicula, Triceratium). Notably, Paralia sulcata showed a shift ∼6 kyrs BP from small to larger cells, possibly reflecting a transition from a coastal to shelf ecosystem. However, microfossils underrepresented lightly silicified planktonic diatoms. Molecular methods detected higher diatom diversity, though up to 50 % of sedaDNA reads remained unclassified due to reference library limitations. Lightly silicified planktonic genera (Chaetoceros, Corethron, Lithodesmium, Rhizosolenia) were identified only via molecular approaches and comprised 73 % of sedaDNA and 88 % of 18S rRNA records. Of 10 shared diatom families, 5, 15, and 4 were unique to microscopy, sedaDNA, and 18S rRNA, respectively. SedaDNA also captured greater benthic diversity.
Our findings revealed limitations in reconstructing historic diatom assemblages from sediment cores. Microfossils faced constraints due to difficulties in morphological identification and preservation biases. In contrast, sedaDNA analysis yielded finer taxonomic resolution, provided access to high-quality reference sequence libraries were available.
{"title":"A 9000-year marine diatom assemblage reconstruction off Eastern Tasmania, Australia, using microfossil and molecular methods","authors":"Bradley Paine , Linda Armbrecht , Christopher Bolch , Gustaaf M. Hallegraeff","doi":"10.1016/j.marmicro.2025.102520","DOIUrl":"10.1016/j.marmicro.2025.102520","url":null,"abstract":"<div><div>Over the past fifty years, Eastern Tasmanian waters have experienced rapid warming, primarily due to the extension of the East Australian Current. This has driven expansion of warm-water biota and decline of those adapted to cooler conditions, including phytoplankton. Presently, plankton monitoring, including diatoms along Eastern Tasmania, spans <100 years. This study reconstructed diatom communities throughout a sediment core spanning 9000 years before present (9 kyrs BP), using microfossil analysis and molecular techniques, including sedimentary ancient DNA (<em>sed</em>aDNA) and 18S rRNA from a 10-year water column archive at the Maria Island IMOS National Reference Station mooring.</div><div>Microfossil analysis revealed a dominance of strongly silicified benthic taxa (<em>Campylodiscus</em>, <em>Diploneis</em>, <em>Paralia</em>, <em>Pyxidicula</em>, <em>Triceratium</em>). Notably, <em>Paralia sulcata</em> showed a shift ∼6 kyrs BP from small to larger cells, possibly reflecting a transition from a coastal to shelf ecosystem. However, microfossils underrepresented lightly silicified planktonic diatoms. Molecular methods detected higher diatom diversity, though up to 50 % of sedaDNA reads remained unclassified due to reference library limitations. Lightly silicified planktonic genera (<em>Chaetoceros</em>, <em>Corethron</em>, <em>Lithodesmium</em>, <em>Rhizosolenia</em>) were identified only via molecular approaches and comprised 73 % of sedaDNA and 88 % of 18S rRNA records. Of 10 shared diatom families, 5, 15, and 4 were unique to microscopy, sedaDNA, and 18S rRNA, respectively. <em>Seda</em>DNA also captured greater benthic diversity.</div><div>Our findings revealed limitations in reconstructing historic diatom assemblages from sediment cores. Microfossils faced constraints due to difficulties in morphological identification and preservation biases. In contrast, <em>sed</em>aDNA analysis yielded finer taxonomic resolution, provided access to high-quality reference sequence libraries were available.</div></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"201 ","pages":"Article 102520"},"PeriodicalIF":1.6,"publicationDate":"2025-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145324391","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-08DOI: 10.1016/j.marmicro.2025.102522
Shokoufeh Mori , Sakineh Arefifard , Thomas J. Algeo , Jonathan D. Schueth
Upper Cretaceous and Paleogene deposits are broadly distributed within the Zagros Basin of western and southwestern Iran, yet a nearly continuous stratigraphic record of the calcareous nannofossil stratigraphy of this region has not been generated to date. Rich and diverse assemblages of calcareous nannofossil are present in the uppermost Cenomanian to Ypresian deposits of the Arkavaz section on the southwestern limb of the Kabir Kuh Anticline. The presence of the taxon Marthasterites furcatus demonstrates a late Turonian age for the base of the section. Two hiatuses were identified: one at the Santonian/Campanian boundary, where the UC13 Biozone is missing, and the other in the lower Campanian, where the UC15a-b Biozone is missing. The bulk of the section is of Campanian age, indicating a high sedimentation rate during that stage. The Cretaceous/Paleogene boundary is marked by abundant calcareous dinoflagellates as well as increased abundances of calcispheres (“Thoracosphaera” sp.) and Neobiscutum. A complete record of key index taxa of Paleocene to lower Eocene biozones NP1–12 is present. We note elevated abundance of Biscutum constans, Discorhabdus ignotus, and Zeugrhabdotus noeliae coeval with the Cenomanian/Turonian boundary (CTB) respectively, similar to records in other Tethyan sections. The PETM interval contains abundant oligotrophic taxa such as Sphenolithus and Zygrhablithus but lacks many of the nannofossil taxa noted elsewhere, whereas other PETM sections in the Tethyan region are characterized by a notable decrease in oligotrophic taxa. The Arkavaz section is a leading target for further study of paleoenvironmental changes and biotic events through the Late Cretaceous to Paleogene.
{"title":"Calcareous nannofossil biostratigraphy of the upper cretaceous to lower Paleocene succession in the Zagros Basin, western Iran: Implications for the OAE2 and PETM events","authors":"Shokoufeh Mori , Sakineh Arefifard , Thomas J. Algeo , Jonathan D. Schueth","doi":"10.1016/j.marmicro.2025.102522","DOIUrl":"10.1016/j.marmicro.2025.102522","url":null,"abstract":"<div><div>Upper Cretaceous and Paleogene deposits are broadly distributed within the Zagros Basin of western and southwestern Iran, yet a nearly continuous stratigraphic record of the calcareous nannofossil stratigraphy of this region has not been generated to date. Rich and diverse assemblages of calcareous nannofossil are present in the uppermost Cenomanian to Ypresian deposits of the Arkavaz section on the southwestern limb of the Kabir Kuh Anticline. The presence of the taxon <em>Marthasterites furcatus</em> demonstrates a late Turonian age for the base of the section. Two hiatuses were identified: one at the Santonian/Campanian boundary, where the UC13 Biozone is missing, and the other in the lower Campanian, where the UC15a-b Biozone is missing. The bulk of the section is of Campanian age, indicating a high sedimentation rate during that stage. The Cretaceous/Paleogene boundary is marked by abundant calcareous dinoflagellates as well as increased abundances of calcispheres (<em>“Thoracosphaera</em>” sp.) and <em>Neobiscutum</em>. A complete record of key index taxa of Paleocene to lower Eocene biozones NP1–12 is present. We note elevated abundance of <em>Biscutum constans</em>, <em>Discorhabdus ignotus</em>, and <em>Zeugrhabdotus noeliae</em> coeval with the Cenomanian/Turonian boundary (CTB) respectively, similar to records in other Tethyan sections. The PETM interval contains abundant oligotrophic taxa such as <em>Sphenolithus</em> and <em>Zygrhablithus</em> but lacks many of the nannofossil taxa noted elsewhere, whereas other PETM sections in the Tethyan region are characterized by a notable decrease in oligotrophic taxa. The Arkavaz section is a leading target for further study of paleoenvironmental changes and biotic events through the Late Cretaceous to Paleogene.</div></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"201 ","pages":"Article 102522"},"PeriodicalIF":1.6,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145267608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-03DOI: 10.1016/j.marmicro.2025.102521
Nguyen Van Su, Nguyen Tan Trieu, Mai Hoang Dam, Nguyen Thi Tham, Bui Thi Ngoc Phuong
This study integrates biostratigraphic and petrographic data from five wells to characterize Miocene sediments in the southeastern Nam Con Son Basin, offshore Vietnam. The Miocene succession is divided into three distinct units. The Lower Miocene (foraminiferal zones M1b–M5, nannofossil zones CNM2–CNM6) consists of sandstone, siltstone, and calcareous claystone deposited in intertidal to middle neritic environments, characterized by low microfossil abundance. The overlying Middle Miocene (M5–M9, CNM7–CNM9) comprises sandstone interbedded with packstone and wackestone and records a significant increase in microfossil abundance and diversity, indicating a transgression into middle to outer neritic settings. A major stratigraphic hiatus, marked by the absence of zones M10–M13a and CNM10–CNM14, separates the Middle from the Upper Miocene. The latter unit (M13b–M14, CNM15–CNM20) is composed of limestone, calcareous claystone, and siliciclastic sediments and exhibits a peak in microfossil abundance and diversity, reflecting continued deepening to outer neritic and upper bathyal conditions. Reservoir quality varies significantly across the succession. While the Lower and Middle Miocene sandstones and Upper Miocene limestones exhibit moderate to good porosity enhanced by grain dissolution, the Lower and Middle Miocene limestones show poor porosity due to cementation. This refined stratigraphic framework significantly improves regional correlation and enhances geological models for future hydrocarbon exploration in the basin.
{"title":"Biostratigraphy and petrography of Miocene sediments in the southeastern Nam Con Son Basin, Vietnam","authors":"Nguyen Van Su, Nguyen Tan Trieu, Mai Hoang Dam, Nguyen Thi Tham, Bui Thi Ngoc Phuong","doi":"10.1016/j.marmicro.2025.102521","DOIUrl":"10.1016/j.marmicro.2025.102521","url":null,"abstract":"<div><div>This study integrates biostratigraphic and petrographic data from five wells to characterize Miocene sediments in the southeastern Nam Con Son Basin, offshore Vietnam. The Miocene succession is divided into three distinct units. The Lower Miocene (foraminiferal zones M1b–M5, nannofossil zones CNM2–CNM6) consists of sandstone, siltstone, and calcareous claystone deposited in intertidal to middle neritic environments, characterized by low microfossil abundance. The overlying Middle Miocene (M5–M9, CNM7–CNM9) comprises sandstone interbedded with packstone and wackestone and records a significant increase in microfossil abundance and diversity, indicating a transgression into middle to outer neritic settings. A major stratigraphic hiatus, marked by the absence of zones M10–M13a and CNM10–CNM14, separates the Middle from the Upper Miocene. The latter unit (M13b–M14, CNM15–CNM20) is composed of limestone, calcareous claystone, and siliciclastic sediments and exhibits a peak in microfossil abundance and diversity, reflecting continued deepening to outer neritic and upper bathyal conditions. Reservoir quality varies significantly across the succession. While the Lower and Middle Miocene sandstones and Upper Miocene limestones exhibit moderate to good porosity enhanced by grain dissolution, the Lower and Middle Miocene limestones show poor porosity due to cementation. This refined stratigraphic framework significantly improves regional correlation and enhances geological models for future hydrocarbon exploration in the basin.</div></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"201 ","pages":"Article 102521"},"PeriodicalIF":1.6,"publicationDate":"2025-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145221334","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-26DOI: 10.1016/j.marmicro.2025.102519
Saki Ishino , Takuya Itaki , Motohisa Fukuda
Recent evidence suggests that object detection techniques based on deep learning are evidently useful for automating microfossil analysis, particularly by enabling the rapid and accurate extraction of target particles. While the assemblage and morphometric analysis of fossil diatoms requires unique procedures, such as including fragmented specimens in counts and accounting for intra-morphometric variation, little is known regarding how these factors affect detection accuracy or how to efficiently construct training datasets for data-driven methods such as deep learning. In this study, we experimentally evaluated the use of the YOLOv5 object detection model to detect Eucampia antarctica, a key paleoenvironmental indicator, across sites in the Southern Ocean that vary in sedimentological and biogeographical characteristics. Detection accuracy was assessed using the datasets from fourteen test sites for the models trained on datasets from four individual sites, that vary within E. antarctica morphology and fossil preservation state, as well as models trained on pairwise combinations of these sites. Our results show that morphological variation of E. antarctica did not significantly affect detection performance, but models trained on datasets of moderately preserved fossils slightly outperformed those trained on datasets of well-preserved fossils. Furthermore, the findings suggest that incorporating diverse non-target particles including other diatom fragments and sediment particles in training data is critical for developing robust models that maintain consistently high performance in diverse regions. Our experiments demonstrate that object detection models allow rapid and accurate counting of E. antarctica, thereby improving its use in paleoenvironmental reconstructions, including past sea ice and surface temperatures.
{"title":"Deep learning object detection for fossil diatom counting: assessing the impact of fossil preservation and intraspecific morphological variation","authors":"Saki Ishino , Takuya Itaki , Motohisa Fukuda","doi":"10.1016/j.marmicro.2025.102519","DOIUrl":"10.1016/j.marmicro.2025.102519","url":null,"abstract":"<div><div>Recent evidence suggests that object detection techniques based on deep learning are evidently useful for automating microfossil analysis, particularly by enabling the rapid and accurate extraction of target particles. While the assemblage and morphometric analysis of fossil diatoms requires unique procedures, such as including fragmented specimens in counts and accounting for intra-morphometric variation, little is known regarding how these factors affect detection accuracy or how to efficiently construct training datasets for data-driven methods such as deep learning. In this study, we experimentally evaluated the use of the YOLOv5 object detection model to detect <em>Eucampia antarctica</em>, a key paleoenvironmental indicator, across sites in the Southern Ocean that vary in sedimentological and biogeographical characteristics. Detection accuracy was assessed using the datasets from fourteen test sites for the models trained on datasets from four individual sites, that vary within <em>E. antarctica</em> morphology and fossil preservation state, as well as models trained on pairwise combinations of these sites. Our results show that morphological variation of <em>E. antarctica</em> did not significantly affect detection performance, but models trained on datasets of moderately preserved fossils slightly outperformed those trained on datasets of well-preserved fossils. Furthermore, the findings suggest that incorporating diverse non-target particles including other diatom fragments and sediment particles in training data is critical for developing robust models that maintain consistently high performance in diverse regions. Our experiments demonstrate that object detection models allow rapid and accurate counting of <em>E. antarctica</em>, thereby improving its use in paleoenvironmental reconstructions, including past sea ice and surface temperatures.</div></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"201 ","pages":"Article 102519"},"PeriodicalIF":1.6,"publicationDate":"2025-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145267607","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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