Journal of Micropalaeontology最新文献

{"title":"Transient micropaleontological turnover across a late Eocene (Priabonian) carbon and oxygen isotope shift on Blake Nose (NW Atlantic)","authors":"Julia de Entrambasaguas, T. Westerhold, H. L. Jones, L. Alegret","doi":"10.5194/jm-43-303-2024","DOIUrl":"https://doi.org/10.5194/jm-43-303-2024","url":null,"abstract":"Abstract. The Gulf Stream, a western boundary current transporting warm water into the North Atlantic, plays a key role in climate regulation and oceanographic stability at a regional and global scale as part of the Atlantic Meridional Overturning Circulation (AMOC). Evidence suggests that an ancestral Gulf Stream has existed since the Mesozoic, and it has altered its course repeatedly over Cenozoic times. In this study, we focus on the upper Eocene (Priabonian, ca. 36 Ma) from Ocean Drilling Program Site 1053 on Blake Nose (subtropical North Atlantic). Bulk carbon and oxygen stable isotopes, as well as benthic foraminiferal and calcareous nannofossil assemblages, provide an integrated assessment of the palaeoceanographic changes impacting the area through the water column to the seafloor. Micropaleontological assemblages suggest changes in surface ocean stratification and nutrient supply to the seafloor coeval with a paired negative carbon and oxygen isotope excursion and the return to background conditions higher up in the study section. These transitory changes are compatible with the longitudinal displacement of the proto-Gulf Stream and its related eddies. Our results build on previous work and support the hypothesis that links palaeoceanographic changes in the Blake Nose area with shifts in the proto-Gulf Stream during the middle and late Eocene.\u0000","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141929400","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}

{"title":"Benthic foraminifers in coastal habitats of Ras Mohamed Nature Reserve, southern Sinai, Red Sea, Egypt","authors":"Ahmed Badreldin, Pamela Hallock","doi":"10.5194/jm-43-239-2024","DOIUrl":"https://doi.org/10.5194/jm-43-239-2024","url":null,"abstract":"Abstract. The Red Sea is globally recognized for its exceptional diversity of marine environments despite relatively high salinities (39–41). Unfortunately, as elsewhere, anthropogenic activities are degrading coastal environments, including coral reefs. We examined foraminiferal distributions to assess the ecological status of coral reef environments in the coastal area of the Ras Mohamed Nature Reserve (RMNR) in the southern Sinai coastal region. Sediment samples were collected in mangrove, shallow-lagoon, nearshore, and coral reef habitats. Overall, 95 species were recorded. Five benthic foraminiferal species that host algal symbionts dominated the assemblages, representing ∼60 % of the assemblages, along with one porcelaneous heterotrophic species (Quinqueloculina seminulum; ∼8 %). The symbiont-bearing species were three porcelaneous forms (Amphisorus hemprichii, Peneroplis pertusus, and P. planatus) and two hyaline taxa (Amphistegina lobifera and A. lessonii). Peneroplis and Amphisorus dominated shallow-bay and mangrove channel assemblages, where carbonate sediments predominated, whereas Amphistegina were most abundant in reef sediments. The results of diversity and heterogeneity indices, including the Shannon–Wiener index (H′), the Simpson index (D), and the evenness index (E), were remarkably consistent. The foraminiferal assemblages are characterized by low diversity (H′), low evenness, and often high dominance (D). Values of the FoRAM Index consistently exceeded four, indicating water quality suitable for carbonate production and accretion. Relatively high percentages of foraminifers were collected live (stained), with up to 18 % of the total assemblage in some localities. The low α-Fisher indices and commonly observed “abnormal” peneroplid and soritid specimens reflect that these metrics must be used with caution when assessing tropical–subtropical shallow-water assemblages in hypersaline environments. Benthic species that host algal symbionts represent a tiny fraction of total numbers of benthic species, yet photosynthesis by the algal symbionts allows the dominance of those few in clear, shallow, reef-associated waters where particulate food is limited. In addition, morphological variability is extremely common in peneroplids and soritids for reasons not fully understood.\u0000","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141653784","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}

{"title":"Pliocene–Pleistocene warm-water incursions and water mass changes on the Ross Sea continental shelf (Antarctica) based on foraminifera from IODP Expedition 374","authors":"Julia L. Seidenstein, R. M. Leckie, R. McKay, L. De Santis, David Harwood","doi":"10.5194/jm-43-211-2024","DOIUrl":"https://doi.org/10.5194/jm-43-211-2024","url":null,"abstract":"Abstract. International Ocean Discovery Program (IODP) Expedition 374 sailed to the Ross Sea in 2018 to reconstruct paleoenvironments, track the history of key water masses, and assess model simulations that show warm-water incursions from the Southern Ocean led to the loss of marine-based Antarctic ice sheets during past interglacials. IODP Site U1523 (water depth 828 m) is located at the continental shelf break, northeast of Pennell Bank on the southeastern flank of Iselin Bank, where it lies beneath the Antarctic Slope Current (ASC). This site is sensitive to warm-water incursions from the Ross Sea Gyre and modified Circumpolar Deep Water (mCDW) today and during times of past warming climate. Multiple incursions of subpolar or temperate planktic foraminifera taxa occurred at Site U1523 after 3.8 Ma and prior to ∼ 1.82 Ma. Many of these warm-water taxa incursions likely represent interglacials of the latest Early Pliocene and Early Pleistocene, including Marine Isotope Stage (MIS) Gi7 to Gi3 (∼ 3.72–3.65 Ma), and Early Pleistocene MIS 91 or 90 (∼ 2.34–2.32 Ma) and MIS 77–67 (∼ 2.03–1.83 Ma) and suggest warmer-than-present conditions and less ice cover in the Ross Sea. However, a moderately resolved age model based on four key events prohibits us from precisely correlating with Marine Isotope Stages established by the LR04 Stack; therefore, these correlations are best estimates. Diatom-rich intervals during the latest Pliocene at Site U1523 include evidence of anomalously warm conditions based on the presence of subtropical and temperate planktic foraminiferal species in what likely correlates with interglacial MIS G17 (∼ 2.95 Ma), and a second interval that likely correlates with MIS KM3 (∼ 3.16 Ma) of the mid-Piacenzian Warm Period. Collectively, these multiple incursions of warmer-water planktic foraminifera provide evidence for polar amplification during super-interglacials of the Pliocene and Early Pleistocene. Higher abundances of planktic and benthic foraminifera during the Mid- to Late Pleistocene associated with interglacials of the MIS 37–31 interval (∼ 1.23–1.07 Ma), MIS 25 (∼ 0.95 Ma), MIS 15 (∼ 0.60 Ma), and MIS 6–5e transition (∼ 0.133–0.126 Ma) also indicate a reduced ice shelf and relatively warm conditions, including multiple warmer interglacials during the Mid-Pleistocene Transition (MPT). A decrease in sedimentation rate after ∼ 1.78 Ma is followed by a major change in benthic foraminiferal biofacies marked by a decrease in Globocassidulina subglobosa and a decrease in mud (< 63 µm) after ∼ 1.5 Ma. Subsequent dominance of Trifarina earlandi biofacies beginning during MIS 15 (∼ 600 ka) indicate progressive strengthening of the Antarctic Slope Current along the shelf edge of the Ross Sea during the mid to Late Pleistocene. A sharp increase in foraminiferal fragmentation after the MPT (∼ 900 ka) and variable abundances of T. earlandi indicate higher productivity, a stronger but variable ASC during interglacials, and/or corrosive ","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141656867","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}

{"title":"Return to the Ross Ice Shelf Project (RISP), Site J-9 (1977–1979): perspectives of West Antarctic Ice Sheet history from Miocene and Holocene benthic foraminifera","authors":"S. Dameron, R. M. Leckie, David Harwood, Reed Scherer, Peter-Noel Webb","doi":"10.5194/jm-43-187-2024","DOIUrl":"https://doi.org/10.5194/jm-43-187-2024","url":null,"abstract":"Abstract. In 1977–1978 and 1978–1979, the Ross Ice Shelf Project (RISP) recovered sediments from beneath the largest ice shelf in Antarctica at Site J-9 (∼82° S, 168° W), ∼450 km from open marine waters at the calving front of the Ross Ice Shelf and 890 km from the South Pole, one of the southernmost sites for marine sediment recovery in Antarctica. One important finding was the discovery of an active macrofauna, including crustaceans and fish, sustained below the ice shelf far from open waters. The sediment has a thin, unconsolidated upper unit (up to 20 cm thick) and a texturally similar but compacted lower unit (>1 m thick) containing reworked early, middle, and late Miocene diatom and calcareous benthic foraminiferal assemblages. A probable post-Last Glacial Maximum (LGM) disconformity separates the upper unit containing a dominantly agglutinated foraminiferal assemblage, from the lower unit consisting mostly of reworked Miocene calcareous benthic species, including Trifarina fluens, Elphidium magellanicum, Globocassidulina subglobosa, Gyroidina sp., and Nonionella spp. The presence of the polar planktic foraminiferal species Neogloboquadrina pachyderma and the endemic Antarcticella antarctica supports the late Miocene diatom age for the matrix of the lower unit. The microfossil assemblages indicate periods of ice sheet collapse and open-water conditions south of Site J-9 during warm intervals of the early, middle, and late Miocene, including the Miocene Climatic Optimum (∼17–14.7 Ma), demonstrating the dynamic nature of the West Antarctic Ice Sheet (WAIS) and Ross Ice Shelf during the Neogene. The foraminiferal assemblage of the upper unit is unique to the Ross Sea and suggests the influence of a sub-ice-shelf water mass proximal to the retreating post-LGM grounding zone. This unique assemblage is strongly dominated by the bathyal, cold-water agglutinated genus Cyclammina.\u0000","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141702702","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}

{"title":"Two new clavate Fragilariopsis and one new Rouxia diatom species with biostratigraphic and paleoenvironmental applications for the Pliocene-Pleistocene, East Antarctica","authors":"Grace Duke, Josie Frazer, B. Taylor-Silva, C. Riesselman","doi":"10.5194/jm-43-139-2024","DOIUrl":"https://doi.org/10.5194/jm-43-139-2024","url":null,"abstract":"Abstract. Three new pennate diatom taxa, Fragilariopsis clava sp. nov. Duke; Fragilariopsis armandae sp. nov. Frazer, Duke et Riesselman; and Rouxia raggattensis sp. nov. Duke et Riesselman, are described and named from Pliocene-Pleistocene sediments collected from the continental rise adjacent to the Wilkes Land coast of East Antarctica. The stratigraphic occurrence of F. clava and F. armandae at IODP Site U1361 are well-constrained to Marine Isotope Stages G9-G7 (2.76–2.74 Ma) and 101–97 (2.58–2.47 Ma), respectively. The short stratigraphic ranges of F. clava and F. armandae are potentially useful biostratigraphic markers for constraining the age of late Pliocene to Early Pleistocene Antarctic sediments. Rouxia raggattensis is observed in the oldest sample examined at Site U1361 from ∼4.05 Ma and is more common between 3.0–2.15 Ma. The rise in abundance of R. raggattensis corresponds to a large turnover in diatom species between 3 and 2 Ma associated with Antarctic cooling, suggesting that sea surface conditions were favorable for R. raggattensis during this dynamic time. Clavate Fragilariopsis species diversified between 2.9–2.7 Ma, but some species quickly went extinct between 2.7–2.5 Ma, possibly because they were marginalized by the cooler climate conditions.\u0000","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141351857","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}

{"title":"Diatom and radiolarian biostratigraphy in the Pliocene sequence of ODP Site 697 (Jane Basin, Atlantic sector of the Southern Ocean)","authors":"Yuji Kato, I. Hernández‐Almeida, Lara F. Pérez","doi":"10.5194/jm-43-93-2024","DOIUrl":"https://doi.org/10.5194/jm-43-93-2024","url":null,"abstract":"Abstract. Bio- and magnetostratigraphic events are essential to construct age models of marine sedimentary sequences for which no other dating methods are available. In this study, we re-visit Ocean Drilling Program (ODP) Leg 113, Hole 697B (drilled in the Jane Basin, the Atlantic sector of the Southern Ocean; 61°48.626′S, 40°17.749′W), to refine diatom and radiolarian biostratigraphy for the early and middle Pliocene, a warm interval of Earth's history which is often considered a climatic analogue for the future. In total, 16 bioevents were identified in the diatom analysis and 3 in the radiolarian analysis. From these, 8 diatom events and one radiolarian event were identified for the first time in Hole 697B. We correlate the identified bioevents with existing paleomagnetic datums in Hole 697B to recalculate and update the ages of the bioevents. Although most of the calculated ages fall within the range of previously published ages, this study allowed us to narrow the age ranges of a number of bioevents. The updated biostratigraphy, as well as the assemblage data presented here, contributes to strengthening the Pliocene chronological framework at Hole 697B for future paleoceanographic work. In addition, we found an interval characterized by abundant reworked Miocene microfossils (e.g., Denticulopsis spp.) at ca. 4.5–3.7 Ma that may suggest sediment disturbance caused by regional tectonic and/or paleoceanographic events in the Southern Ocean during this time interval.\u0000","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140963847","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}

{"title":"The response of ostracod faunal assemblages to hydrology, lake level, and carbon cycling in a Jamaican marl lake: a palaeolimnological investigation","authors":"Hannah Greenway, Jonathan Holmes, Michael Burn","doi":"10.5194/jm-43-81-2024","DOIUrl":"https://doi.org/10.5194/jm-43-81-2024","url":null,"abstract":"Abstract. Ostracod taxa from shallow freshwater lakes are sensitive to a range of limnological factors including temperature, hydrological habitat, lake level, and the distribution of aquatic plants. Ostracod assemblages preserved in Quaternary lake sediments can be used to reconstruct limnological change and are therefore potentially valuable palaeoenvironmental proxies. However, lack of autecological information about some taxa may limit the validity of such reconstructions. We use fossil ostracod assemblages recovered from radiocarbon-dated late Holocene sediments from Wallywash Great Pond, a small, shallow freshwater lake in southwestern Jamaica, to reconstruct limnological change over the past ∼ 1800 years. We circumvent ongoing taxonomic and ecological uncertainties associated with the identification of fossil ostracod taxa by drawing on observations of the ecology of ostracods found living in Jamaican water bodies. By combining this information with limnological data from the extant lake, and with sedimentological and isotopic data from the lake sediments, we show that a published interpretation of ostracod assemblages for the late Quaternary of Wallywash Great Pond is simplistic, at least for the late Holocene section of the sediment record. We conclude that changes in ostracod assemblages are linked to variations in the input of undersaturated groundwater to the northern part of the lake from which the core was recovered. These variations, which were driven by changes in the precipitation / evaporation ratio (effective moisture), also controlled sedimentation, with reduced effective moisture and a decline in undersaturated groundwater input favouring marl precipitation, whereas organic sediments are linked to increased effective moisture and enhanced groundwater input. Our findings suggest that the dramatic shifts in ostracod assemblages at this site are a complex response to changes in hydrology, sedimentology, and carbonate saturation rather than being a simple indicator of lake-level change. Combining ostracod assemblage data with the results of other palaeolimnological analyses also allows more detailed reconstructions to be made for this lake, and such a multiproxy approach is recommended for similar lakes elsewhere.\u0000","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140974712","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}

{"title":"Progress in the taxonomy of Late Cretaceous high-latitude radiolarians: insights from the Horton River area, Northwest Territories, Canada","authors":"Juan F. Diaz, Noritoshi Suzuki, Jennifer M. Galloway, M. Bringué","doi":"10.5194/jm-43-69-2024","DOIUrl":"https://doi.org/10.5194/jm-43-69-2024","url":null,"abstract":"Abstract. Radiolarians have proven to be exceptional tools in biostratigraphic and paleoenvironmental studies despite their relatively low preservation potential in the sedimentary record. Reports of Upper Cretaceous radiolarians in high northern latitudes are scant, and their taxonomy is not often discussed in the few reports available in the literature. In this study, we describe one new genus and three new species of polycystine radiolarians from Upper Cretaceous strata of the northern mainland coast of Arctic Canada. The specimens were recovered from the Santonian–middle Campanian Smoking Hills Formation and the middle Campanian–Maastrichtian Mason River Formation and are assigned to the genus Canadasphaera n. gen. (Order Spumellaria) and the species Canadasphaera inuita n. sp., Kuppelella rusti n. sp., and Lithocampe? rara n. sp. The taxonomic notes provided in this study improve our understanding of Late Cretaceous radiolarians from high northern latitudes and serve as a foundation for future Cretaceous radiolarian research in Arctic regions. Canadasphaera: urn:lsid:zoobank.org:act:C6B7B702-4B74-472D-8893-0A41B93A5066, date of registration: 19 April 2024 Canadasphaera inuita: urn:lsid:zoobank.org:act:C30E555B-EE94-4680-87D1-5CE83E128461, date of registration: 19 April 2024 Kuppelella rusti: urn:lsid:zoobank.org:act:68ECB628-2E74-4748-ACA4-DD1A33B05837, date of registration: 19 April 2024 Lithocampe? rara: urn:lsid:zoobank.org:act:25E569B2-93A8-425F-BB7C-D29A0437763F, date of registration: 19 April 2024\u0000","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141017235","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}

{"title":"Nannofossils from the Middle Eocene Sabiñánigo Sandstone Formation in the Jaca Basin (southern Pyrenees): biostratigraphy and paleoenvironmental implications","authors":"Elizabeth R. Lasluisa, O. Oms, E. Remacha, A. González-Lanchas, Hug Blanchar-Roca, J. Flores","doi":"10.5194/jm-43-55-2024","DOIUrl":"https://doi.org/10.5194/jm-43-55-2024","url":null,"abstract":"Abstract. This study presents the first detailed data on calcareous nannofossil assemblages from the Sabiñánigo Sandstone Formation in the Jaca Basin (central south Pyrenees). This formation is mainly composed of deltaic and outer-shelf sediments. These siliciclastic deposits contain nannofossil assemblages that are moderately to well-preserved, particularly in fine-grained levels. They contain a calcareous nannofossil assemblage dominated by the species Cyclicargolithus floridanus, Coccolithus pelagicus, Coccolithus formosus, Clausicoccus fenestratus, Zygrhablithus bijugatus, and several species of Sphenolithus and Chiasmolithus. The biostratigraphic results enabled the characterization of the Middle Eocene biohorizons, based on global stratigraphic scales and the improvement of the temporal correlation and lateral evolution of this basin's deposits. The sedimentary sequence of the Sabiñánigo Sandstone was deposited during the Middle Eocene, between the upper part of biozone NP16 and the base of NP17, in the Bartonian. The calcareous nannoplankton assemblage suggests warm and oligotrophic surface waters for the Bartonian interval in the Jaca Basin.\u0000","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140713077","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}

{"title":"Radiolarian assemblages related to the ocean–ice interaction around the East Antarctic coast","authors":"M. Iizuka, Takuya Itaki, Osamu Seki, Ryosuke Makabe, Motoha Ojima, Shigeru Aoki","doi":"10.5194/jm-43-37-2024","DOIUrl":"https://doi.org/10.5194/jm-43-37-2024","url":null,"abstract":"Abstract. The Southern Ocean plays a central role in Earth's climate, ecology, and biogeochemical cycles. Therefore, understanding long-term changes in Southern Ocean water masses in the geologic past is essential for assessing the role of the Southern Ocean in the climate system. Radiolarian fossils are a useful tool to reconstruct the water masses of the Southern Ocean. However, the radiolarian assemblages in the high latitudes of the Southern Ocean (south of the polar front (PF)) are still poorly understood. In this paper, we report the radiolarian assemblages in surface marine sediment and plankton tow samples collected from the high latitudes south of the PF. In the surface sediments, four factors (named F1–F4) of the radiolarian assemblages were identified using Q-mode factor analysis, which are related to different water masses and hydrological conditions. F1 is related to the surface waters south of the southern boundary (SB) of the Antarctic Circumpolar Current (ACC), which are cooled by melting sea ice and ice sheets. F2 is associated with water masses north of the SB. A comparison with the vertical distribution of the radiolarian assemblages in plankton tow samples indicates that characteristic species are associated with the Circumpolar Deep Water (CDW) and surface waters north of the SB. F3 is associated with modified Circumpolar Deep Water (mCDW). The radiolarian assemblage of F4 does not seem specifically related to any of the water mass here analyzed. However, the species in this assemblage are typically dwells within ice shelf and/or sea ice edge environments. Radiolarian assemblages here identified and associated with water masses, and ice edge environments are useful to reconstruct the environment south of the PF in the geologic past.\u0000","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139599210","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}