Marine Micropaleontology最新文献

Are there marine sedimentary losses and transgressions in the Southeast Bohai Sea during MIS 2-MIS 3?

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-03-27 DOI: 10.1016/j.marmicro.2025.102461

Qingtong Wang , Gayan Bandara , Wenqin Jiang , Feifei Wang , Hongxian Chu , Meiling Yin , Chuanxiu Luo

Sedimentary architecture dominated by transgression–regression cycles in the shallow Bohai shelf region contains information about global sea-level, climate and local tectonics. However, previous studies of transgression–regression cycles in this region at orbital timescales that extend back to the early Pleistocene are sparse. In this study, we present an integrated sedimentological, paleontological study of a 32.49 m (93kyr BP) core (HZK02) recovered from the Bohai Sea, China, for which an AMS ¹⁴C and five OSL dates-based age model is available. Compared with previous pollen study in the Bohai area, the results show that there were two significant transgressions that occur in MIS 5c, top part of MIS 2 and MIS 1, with abundant foraminifera from the near shore shallow sea of the continental shelf, corresponding with prevailing arboreal pollen dominated by Pinus and Quercus. While, terrestrial herbs such as Artemisia and Chenopodiaceae dominated during colder periods, such as MIS 4, MIS 5b, when sea levels dropped significantly, corresponding with a scarcity of foraminifera in terrestrial sediment layers from MIS 5b, MIS 5a, MIS 4, and MIS 3. We find that at depth of 8.18–6.10 m, with depth of only 2.08 m and very high sediment rate, the duration age last from 64,100 yr BP to 10,500 yr BP, which might indicate some missing part of the deposition of MIS 3 and MIS 2. The transgressions signal has been found in top part of MIS 2 sediment, hardly in MIS 3.

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引用次数: 0

Siliceous plankton flux and radiolarian community structure in the highly oligotrophic Ionian Sea (Eastern Mediterranean) – Imprints of climate variability

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-03-13 DOI: 10.1016/j.marmicro.2025.102460

Marie Cueille , Taniel Danelian , Dimitra-Ioli Skouroliakou , Elisavet Skampa , Maria Triantaphyllou , Alexandra Gogou , Georgia Kambouri , Ioanna Stavrakaki , Koen Sabbe

Based on sediment-trap material collected at 700 m depth from the oligotrophic southern Ionian Sea (Nestor site), this study explores for the first time the impact of seasonal and multiannual (2015–2017) climate variability on the siliceous plankton flux and radiolarian community structure at species level in the Eastern Mediterranean Sea. A total of 143 radiolarian taxa were identified, most of them at the species level. Juveniles represented 35–70 % of the total radiolarian flux. Thirty-nine diatom taxa were identified, including some freshwater species. Coinciding with organic carbon, opal and total mass fluxes, radiolarians and diatoms displayed rather similar pattern in seasonal flux variations, including two seasonal peaks. The first one was recorded in late winter (late February) 2015; it is regarded as the result of late winter intensification of water column mixing. The second peak in the siliceous plankton flux was recorded in late summer to early fall (August – September) of both years 2015 and 2017. This peak is interpreted to be the result of a local upwelling event following the reduced influence of the Pelops anticyclonic gyre. A third productivity event was recorded in April and May 2016, and is interpreted as being influenced by North African dust depositions. Despite the incompleteness of our sediment trap data series, our dataset is valuable as it is the first ever study conducted to the species level on polycystine radiolarian vertical export rates in the Mediterranean Sea, combined with insights into the temporal dynamics of siliceous zoo- and phytoplankton fluxes in the EMed.

{"title":"Siliceous plankton flux and radiolarian community structure in the highly oligotrophic Ionian Sea (Eastern Mediterranean) – Imprints of climate variability","authors":"Marie Cueille , Taniel Danelian , Dimitra-Ioli Skouroliakou , Elisavet Skampa , Maria Triantaphyllou , Alexandra Gogou , Georgia Kambouri , Ioanna Stavrakaki , Koen Sabbe","doi":"10.1016/j.marmicro.2025.102460","DOIUrl":"10.1016/j.marmicro.2025.102460","url":null,"abstract":"<div><div>Based on sediment-trap material collected at 700 m depth from the oligotrophic southern Ionian Sea (Nestor site), this study explores for the first time the impact of seasonal and multiannual (2015–2017) climate variability on the siliceous plankton flux and radiolarian community structure at species level in the Eastern Mediterranean Sea. A total of 143 radiolarian taxa were identified, most of them at the species level. Juveniles represented 35–70 % of the total radiolarian flux. Thirty-nine diatom taxa were identified, including some freshwater species. Coinciding with organic carbon, opal and total mass fluxes, radiolarians and diatoms displayed rather similar pattern in seasonal flux variations, including two seasonal peaks. The first one was recorded in late winter (late February) 2015; it is regarded as the result of late winter intensification of water column mixing. The second peak in the siliceous plankton flux was recorded in late summer to early fall (August – September) of both years 2015 and 2017. This peak is interpreted to be the result of a local upwelling event following the reduced influence of the Pelops anticyclonic gyre. A third productivity event was recorded in April and May 2016, and is interpreted as being influenced by North African dust depositions. Despite the incompleteness of our sediment trap data series, our dataset is valuable as it is the first ever study conducted to the species level on polycystine radiolarian vertical export rates in the Mediterranean Sea, combined with insights into the temporal dynamics of siliceous zoo- and phytoplankton fluxes in the EMed.</div></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"196 ","pages":"Article 102460"},"PeriodicalIF":1.5,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143704044","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}

引用次数: 0

Phyletic evolution of calcareous nannofossil species Reticulofenestra oamaruensis: An example of microevolution preserved at IODP Site U1553 (Southern Pacific Ocean)

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-02-26 DOI: 10.1016/j.marmicro.2025.102452

Valentina Catelli , Davide Persico , Davide Righi , Isabella Raffi , Chiara Fioroni , Giuliana Villa

The IODP Expedition 378 in the Southern Ocean (Campbell Plateau) recovered a Paleogene sedimentary section at Site U1553, cored through multiple holes (A - E) in the late Eocene-early Oligocene interval. Stratigraphic continuity and good preservation of calcareous nannofossils offered the opportunity to study the phyletic origin of Reticulofenestra oamaruensis, the biostratigraphic marker for the Eocene/Oligocene Transition (EOT) in the Southern Ocean (SO). We performed biometric and morphological analyses on R. oamaruensis and the related species Reticulofenestra clatrata, revealing intermediate morphotypes with characters between R. clatrata and R. oamaruensis. These transitional morphotypes, labeled Reticulofenestra transitional form 1 (R. t1) and Reticulofenestra transitional form 2 (R. t2), differ in size from the end members and are distinguished in two size categories: 10–12 μm and 12–14 μm respectively. The intraspecific evolutionary trend shows a gradual size increase of R. clatrata(8–10 μm) that, through intermediate steps represented by R. t1 and R. t2, leads to R. oamaruensis (≥14 μm). The two morphotypes are included in the species identification of R. oamaruensis and enter the stratigraphic record at successive levels, thus delineating a “lineage zone” useful in SO biostratigraphy. R. clatrata and medium – large R. oamaruensis disappear close to the Eocene/Oligocene Boundary. Based on the morphological homology, the progressively increasing size trend from R. clatrata to R. oamaruensis, their stratigraphic range continuity, and their same geographical distribution, we document a phyletic strain endemic to high southern latitudes, of which R. clatrata would represent the archetype.

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引用次数: 0

An integrative analysis of Plectocapillus antarcticus gen. et sp. nov. from Antarctica: Morphology, chemical composition, and phylogeny

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-02-17 DOI: 10.1016/j.marmicro.2025.102451

Somin Lee , Michael A. Kaminski , Fabrizio Frontalini , Jisu Yeom , Nayeon Park , Wonchoel Lee

In this study, Plectocapillus antarcticus gen. et sp. nov., belonging to the Family Pseudobolivinidae Wiesner, 1931, Superfamily Spiroplectamminoidea Cushman, 1927, was described from Maxwell Bay, King George Island, Antarctica. The species is distinguished by its elongate, slender, and entirely biserial test, fragile, thin agglutinated wall, a globular, organic proloculus, and the areal, rounded to arch-like aperture. Notably, this species previously assigned taxonomically as Spiroplectammina filiformis Earland, 1934 or Textularia tenuissima Earland, 1933, in nearby areas. However, morphological comparison revealed differences in chamber arrangement, biserial pair number, test width, and proloculus wall composition. SEM-DES analysis identified Al, Ca, Fe, Mg, Si, and Ti as major chemical elements present in the test wall, along with the traces of K, Mn, Na, P, Ce, Cl, F, S, Sr, and Zr. Phylogenetic analysis of partial SSU rRNA and mitochondrial COI gene sequences confirmed that P. antarcticus forms a well-supported clade, sister to Spiroplectammina biformis. The slender, flexible test, organic proloculus, and inclusion of heavy element-rich minerals suggests potential adaptation to hypoxic or interstitial habitats. By integrating morphological, chemical, and molecular data, this study contributes to the expanding fundamental database and understanding of Antarctic foraminiferal diversity and emphasizes the necessity for continued research in the region.

本研究描述了来自南极洲乔治王岛马克斯韦尔湾的 Plectocapillus antarcticus gen.该物种的特征是其细长、完全双列的试管，脆弱、薄的凝集壁，球状、有机的原核，以及圆形至拱形的等距孔。值得注意的是，该物种以前在附近地区被归类为 Spiroplectammina filiformis Earland, 1934 或 Textularia tenuissima Earland, 1933。然而，通过形态学比较发现，它们在腔室排列、双列对数、测试宽度和原核壁组成方面存在差异。SEM-DES 分析表明，Al、Ca、Fe、Mg、Si 和 Ti 是试验壁中存在的主要化学元素，此外还有微量的 K、Mn、Na、P、Ce、Cl、F、S、Sr 和 Zr。对部分 SSU rRNA 和线粒体 COI 基因序列进行的系统进化分析证实，南极蛙形成了一个支持良好的支系，是双形蛙的姊妹蛙。纤细、柔韧的试管、有机的增殖体以及富含重元素的矿物质表明，南极蛛可能适应缺氧或间隙栖息地。通过整合形态学、化学和分子数据，该研究为不断扩大的基础数据库和对南极有孔虫多样性的了解做出了贡献，并强调了在该地区继续开展研究的必要性。

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引用次数: 0

Sessile foraminifera from mobile substrates: Hidden organisms and big mistakes – The essential is invisible to the eyes

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-02-15 DOI: 10.1016/j.marmicro.2025.102450

Joicce Dissenha , Sibelle Trevisan Disaró , José Rodolfo Angulo , Rodrigo Aluizio

Two case studies conducted on the inner continental shelf off southeastern Brazil revealed an unexpectedly high abundance and diversity of foraminifera attached to or encrusted in sediment grains. Samples were stained with Rose Bengal, fixed in formalin, and subjected to trichloroethylene flotation to isolate free foraminifera. Following screening, the residual fraction was rigorously examined, uncovering numerous attached individuals and robust agglutinate forms that incorporate sediment grains into their tests. This fauna includes little-known genera rarely documented in unconsolidated mobile substrates. Comparisons between floated and residual fractions revealed notable discrepancies, emphasizing the underestimation of sessile and robust forms when residual fractions are overlooked. Neglecting these forms can compromise environmental and paleoenvironmental interpretations, as rarefaction curves illustrate, particularly in high-hydrodynamic regions typically seen as challenging environments for fauna. This study underscores the importance of including sessile foraminifera in biodiversity assessments in dynamic marine areas. We propose a new zone, the “high-hydrodynamic inner coastal shelf,” for Murray's (1973) ternary diagram. Additionally, our findings indicate that inadequate screening methods may leave significant gaps in taxonomic records. Many attached foraminifera remain “invisible to the eye” of researchers, often due to their shape, a lack of prior knowledge, or insufficient attention, resulting in underestimations of their density and richness. Consequently, these organisms are often overlooked in environmental characterizations, taxonomic records, and especially in paleoecological studies and monitoring efforts.

{"title":"Sessile foraminifera from mobile substrates: Hidden organisms and big mistakes – The essential is invisible to the eyes","authors":"Joicce Dissenha , Sibelle Trevisan Disaró , José Rodolfo Angulo , Rodrigo Aluizio","doi":"10.1016/j.marmicro.2025.102450","DOIUrl":"10.1016/j.marmicro.2025.102450","url":null,"abstract":"<div><div>Two case studies conducted on the inner continental shelf off southeastern Brazil revealed an unexpectedly high abundance and diversity of foraminifera attached to or encrusted in sediment grains. Samples were stained with Rose Bengal, fixed in formalin, and subjected to trichloroethylene flotation to isolate free foraminifera. Following screening, the residual fraction was rigorously examined, uncovering numerous attached individuals and robust agglutinate forms that incorporate sediment grains into their tests. This fauna includes little-known genera rarely documented in unconsolidated mobile substrates. Comparisons between floated and residual fractions revealed notable discrepancies, emphasizing the underestimation of sessile and robust forms when residual fractions are overlooked. Neglecting these forms can compromise environmental and paleoenvironmental interpretations, as rarefaction curves illustrate, particularly in high-hydrodynamic regions typically seen as challenging environments for fauna. This study underscores the importance of including sessile foraminifera in biodiversity assessments in dynamic marine areas. We propose a new zone, the “high-hydrodynamic inner coastal shelf,” for Murray's (1973) ternary diagram. Additionally, our findings indicate that inadequate screening methods may leave significant gaps in taxonomic records. Many attached foraminifera remain “invisible to the eye” of researchers, often due to their shape, a lack of prior knowledge, or insufficient attention, resulting in underestimations of their density and richness. Consequently, these organisms are often overlooked in environmental characterizations, taxonomic records, and especially in paleoecological studies and monitoring efforts.</div></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"195 ","pages":"Article 102450"},"PeriodicalIF":1.5,"publicationDate":"2025-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143463598","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}

引用次数: 0

Dinoflagellate cyst assemblages in recent sediments of Iran's tropical mangrove forests

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-02-08 DOI: 10.1016/j.marmicro.2025.102449

Gilan Attaran-Fariman , Sima Abir , Faezeh Dolatabadi , Ehsan Abedi , Fatemeh Sayareh

We investigated the distribution and composition of dinoflagellate cysts, including potential harmful algal bloom (HAB) species, in Iranian mangroves bordering the Persian Gulf and Oman Sea. Sediment samples were collected from 62 stations across 10 locations in three provinces (Bushehr, Hormozgan, Sistan & Baluchestan) in autumn 2020. Analysis of dinoflagellate cysts revealed a diverse assemblage encompassing 56 species, including 10 known to be triggers of harmful algal blooms (HABs). Genus Protoperidinium was dominant, exhibiting a 21.4 % abundance and comprising 14 species across 60 sampling stations. In contrast, genus Margalefidinium was present in 34 stations with only a single species. Margalefidinium polykrikoides was the key species of dissimilarity between provinces, driving distinct compositions in all pairwise comparisons. Scrippsiella acuminata was a significant contributor to the dissimilarity observed between the Bu and S&B, as well as the Ho and S&B assemblages. DistLM, dbRDA, and marginal tests confirmed that environmental parameters significantly (P > 0.05) influenced cyst composition across the provinces. Regular monitoring of environmental parameters alongside analyses of dinoflagellate cyst assemblages is a potential use for predicting HABs and also provide valuable insights into the well-being of essential mangrove ecosystems.

{"title":"Dinoflagellate cyst assemblages in recent sediments of Iran's tropical mangrove forests","authors":"Gilan Attaran-Fariman , Sima Abir , Faezeh Dolatabadi , Ehsan Abedi , Fatemeh Sayareh","doi":"10.1016/j.marmicro.2025.102449","DOIUrl":"10.1016/j.marmicro.2025.102449","url":null,"abstract":"<div><div>We investigated the distribution and composition of dinoflagellate cysts, including potential harmful algal bloom (HAB) species, in Iranian mangroves bordering the Persian Gulf and Oman Sea. Sediment samples were collected from 62 stations across 10 locations in three provinces (Bushehr, Hormozgan, Sistan & Baluchestan) in autumn 2020. Analysis of dinoflagellate cysts revealed a diverse assemblage encompassing 56 species, including 10 known to be triggers of harmful algal blooms (HABs). Genus <em>Protoperidinium</em> was dominant, exhibiting a 21.4 % abundance and comprising 14 species across 60 sampling stations. In contrast, genus <em>Margalefidinium</em> was present in 34 stations with only a single species. <em>Margalefidinium polykrikoides</em> was the key species of dissimilarity between provinces, driving distinct compositions in all pairwise comparisons. <em>Scrippsiella acuminata</em> was a significant contributor to the dissimilarity observed between the Bu and S&B, as well as the Ho and S&B assemblages. DistLM, dbRDA, and marginal tests confirmed that environmental parameters significantly (<em>P</em> > 0.05) influenced cyst composition across the provinces. Regular monitoring of environmental parameters alongside analyses of dinoflagellate cyst assemblages is a potential use for predicting HABs and also provide valuable insights into the well-being of essential mangrove ecosystems.</div></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"195 ","pages":"Article 102449"},"PeriodicalIF":1.5,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143378431","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}

引用次数: 0

Orbital-scale biotic and paleoceanographic changes in Japan Sea during the late Miocene global cooling (LMGC)

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-01-28 DOI: 10.1016/j.marmicro.2025.102448

Mizuki Tojima , Masayuki Ikeda , Kenji M. Matsuzaki

The late Miocene global cooling (LMGC; ca. 7.9–5.8 Ma) was accompanied by global environmental changes including monsoon intensity, ocean circulation, and biotic turnover. Recent studies have revealed drastic environmental and biotic changes in the Japan Sea across the LMGC; the radiolarian fauna in the Japan Sea suggested decreased inflow of Pacific Central Water (PCW) species Tricolocapsa papillosa, increased subarctic species Cycladophora sphaeris and extinction of a dominant endemic radiolarian Cycladophora nakasekoi. These radiolarian fluxes showed ∼100-kyr eccentricity signals; however, the dominant paleoclimatic/paleoceanographic signal during the LMGC appeared to be ∼40-kyr obliquity cycle, which was not detected in the radiolarian fluxes possibly due to lower sampling resolution. Thus, orbital-scale variations of these radiolarian fluxes and their potential forcing mechanisms remain unclear.

In this study, we establish changes in the abundance of selected radiolarian species with a resolution that exceeds the 10-kyrs and suggest obliquity-paced changes in the paleoceanography in the Japan Sea during the LMGC. We detected ∼40-kyr cycles in abundance of T. papillosa, suggesting that PCW inflow into the Japan Sea was controlled by a 40-kyr obliquity-paced glacial cycle. We also detected a ∼ 40-kyr signal in C. sphaeris abundance, implying that the obliquity-paced winter monsoon probably promoted the inflow of subarctic water into the Japan Sea. Contrary, variation in C. nakasekoi abundance lacks a ∼ 40-kyr signal. A 100-kyr cycle is also observed in a summer monsoon proxy from lacustrine sediment in China. Hence, it is possible that C. nakasekoi decreased with weakened summer monsoon across the LMGC.

{"title":"Orbital-scale biotic and paleoceanographic changes in Japan Sea during the late Miocene global cooling (LMGC)","authors":"Mizuki Tojima , Masayuki Ikeda , Kenji M. Matsuzaki","doi":"10.1016/j.marmicro.2025.102448","DOIUrl":"10.1016/j.marmicro.2025.102448","url":null,"abstract":"<div><div>The late Miocene global cooling (LMGC; ca. 7.9–5.8 Ma) was accompanied by global environmental changes including monsoon intensity, ocean circulation, and biotic turnover. Recent studies have revealed drastic environmental and biotic changes in the Japan Sea across the LMGC; the radiolarian fauna in the Japan Sea suggested decreased inflow of Pacific Central Water (PCW) species <em>Tricolocapsa papillosa,</em> increased subarctic species <em>Cycladophora sphaeris</em> and extinction of a dominant endemic radiolarian <em>Cycladophora nakasekoi</em>. These radiolarian fluxes showed ∼100-kyr eccentricity signals; however, the dominant paleoclimatic/paleoceanographic signal during the LMGC appeared to be ∼40-kyr obliquity cycle, which was not detected in the radiolarian fluxes possibly due to lower sampling resolution. Thus, orbital-scale variations of these radiolarian fluxes and their potential forcing mechanisms remain unclear.</div><div>In this study, we establish changes in the abundance of selected radiolarian species with a resolution that exceeds the 10-kyrs and suggest obliquity-paced changes in the paleoceanography in the Japan Sea during the LMGC. We detected ∼40-kyr cycles in abundance of <em>T</em><em>.</em> <em>papillosa</em>, suggesting that PCW inflow into the Japan Sea was controlled by a 40-kyr obliquity-paced glacial cycle. We also detected a ∼ 40-kyr signal in <em>C</em><em>.</em> <em>sphaeris</em> abundance, implying that the obliquity-paced winter monsoon probably promoted the inflow of subarctic water into the Japan Sea. Contrary, variation in <em>C</em><em>.</em> <em>nakasekoi</em> abundance lacks a ∼ 40-kyr signal. A 100-kyr cycle is also observed in a summer monsoon proxy from lacustrine sediment in China. Hence, it is possible that <em>C</em><em>.</em> <em>nakasekoi</em> decreased with weakened summer monsoon across the LMGC.</div></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"195 ","pages":"Article 102448"},"PeriodicalIF":1.5,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143148817","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The biostratigraphy and palaeobiogeography of the Late Jurassic dinoflagellate cysts from the Binalud Mountains, NE Iran

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-01-27 DOI: 10.1016/j.marmicro.2025.102446

Behnaz Kalanat , Elham Davtalab , Ahmad Raoufian

This study investigates the dinoflagellate cysts from the upper part of the Dalichai Formation in the Binalud Mountains (NE Iran, western Tethys), where the deposits are primarily consist of shale and marlstone layers. The analyzed section yielded common and diverse dinoflagellate cyst assemblages comprising 46 species belonging to 33 genera. These assemblages are correlated with the DSJ24–DSJ33 dinoflagellate cyst Zones of the Late Jurassic (late Oxfordian–Tithonian) in the Northern Hemisphere. Key bioevents identified in this interval included the last occurrences of Compositosphaeridium polonicum in the late Oxfordian, the last occurrence of Ctenidodinium ornatum at the Oxfordian–Kimmeridgian boundary, the last occurrences of Tubotuberella eisenackii and Scriniodinium crystallinum in the early Kimmeridgian, and the last occurrence Endoscrinium luridum around the Kimmeridgian–Tithonian boundary. The dinoflagellate cyst assemblages exhibit strong similarities to the flora of the western Tethys (the Middle East, Europe, eastern North America, and North Africa) and are marked differences from coeval assemblages of the eastern Tethys (Australasia, eastern Asia, and northeastern India), reflecting significant provincialism between the western and eastern Tethys during the Late Jurassic.

{"title":"The biostratigraphy and palaeobiogeography of the Late Jurassic dinoflagellate cysts from the Binalud Mountains, NE Iran","authors":"Behnaz Kalanat , Elham Davtalab , Ahmad Raoufian","doi":"10.1016/j.marmicro.2025.102446","DOIUrl":"10.1016/j.marmicro.2025.102446","url":null,"abstract":"<div><div>This study investigates the dinoflagellate cysts from the upper part of the Dalichai Formation in the Binalud Mountains (NE Iran, western Tethys), where the deposits are primarily consist of shale and marlstone layers. The analyzed section yielded common and diverse dinoflagellate cyst assemblages comprising 46 species belonging to 33 genera. These assemblages are correlated with the DSJ24–DSJ33 dinoflagellate cyst Zones of the Late Jurassic (late Oxfordian–Tithonian) in the Northern Hemisphere. Key bioevents identified in this interval included the last occurrences of <em>Compositosphaeridium polonicum</em> in the late Oxfordian, the last occurrence of <em>Ctenidodinium ornatum</em> at the Oxfordian–Kimmeridgian boundary, the last occurrences of <em>Tubotuberella eisenackii</em> and <em>Scriniodinium crystallinum</em> in the early Kimmeridgian, and the last occurrence <em>Endoscrinium luridum</em> around the Kimmeridgian–Tithonian boundary. The dinoflagellate cyst assemblages exhibit strong similarities to the flora of the western Tethys (the Middle East, Europe, eastern North America, and North Africa) and are marked differences from coeval assemblages of the eastern Tethys (Australasia, eastern Asia, and northeastern India), reflecting significant provincialism between the western and eastern Tethys during the Late Jurassic.</div></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"195 ","pages":"Article 102446"},"PeriodicalIF":1.5,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143098473","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}

引用次数: 0

Variations in the morphometric characteristics of Fragilariopsis kerguelensis in the Southwest Pacific sector of the Southern Ocean over the past 40,000 years

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-01-27 DOI: 10.1016/j.marmicro.2025.102447

Xavier Crosta, Thibault Sutre

High-throughput measurements demonstrated the presence of two morphotypes of Fragilariopsis kerguelensis in the Atlantic sector of the Southern Ocean, the proportions of which in downcore samples may be used to reconstruct past sea-surface temperatures quantitatively. We here measured the mean length, width, area, and rectangularity in core SO136–111 to assess variations in both morphotypes in the Polar Front Zone of the western Pacific sector of the Southern Ocean over the past 40,000 years. Mean length, width, and area increased rapidly at the end of the glacial period when the Polar Front migrated southward to reach the core site, ocean temperature increased, and sea ice was no longer present. In contrast, mean rectangularity decreased at the end of the glacial period, when the proportion of the cold-water, high-rectangularity morphotype declined as the ocean warmed at the core site. Downcore patterns and quantitative values of all morphometric characteristics in the southwest Pacific sector agree well with previous studies from the Atlantic sector, suggesting the presence of a similar population of F. kerguelensis in the open Southern Ocean. Nevertheless, rectangularity-based relationships can ultimately produce unrealistic estimates of sea-surface temperatures in core SO136–111 when the proportion of the high-rectangularity morphotype is too low, indicating that these approaches are now limited to temperatures below 3–4 °C.

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引用次数: 0

Distribution of Miocene dinoflagellate cysts in the paralic basins of Tunisia: Paleogeographic and paleoecological reconstruction and eustatic movements

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-01-19 DOI: 10.1016/j.marmicro.2025.102443

Nadia Ben Moktar , Amel Mahjoubi-Ghanmi , Beya Mannai-Tayech

The Miocene deposits of northeastern and central-eastern Tunisia are primarily of clastic, deltaic-type. These deposits are organized into complex sedimentary sequences shaped by tectonic activity, eustatic fluctuations, and changes in climatic conditions. This study presents the evolution of dinoflagellate cysts associations extracted from Miocene-age deposits. These deposits ranged from 16 million to 5.3 million years ago. They are taken from three boreholes and three sections in northeastern and central Tunisia. Dinocysts serve as valuable indicators of climatic variations and sea-level fluctuations. Their study supports the results obtained from the analysis of pollen grains. It sheds light on paleoecology, paleogeography, and eustatic conditions during that period.

Various associations (oceanic, neritic, climatic, etc.) were established based on the ecological preferences of these marine microorganisms. Oceanic conditions are characterized by the presence of Impagidinium. Shallow marine environments are defined by the presence of Cordosphaeridium inodes minimus. Meanwhile, Nematosphaeropis and Tectatodinium indicate a neritic to oceanic environment. It is confirmed by the abundance of Lejeunecysta, Operculodinium, israelianum, Polysphardium zoharyi, Homotryblium, Spiniferites, Cleistosphaeridium, and Lingulodinium machaerophorum. These results align with lithological and biostratigraphic data related to paleobathymetry and paleogeography.

Changes in dinocyst taxa relative abundances helped track the shoreline's evolution during the Miocene. Variations in the relative abundance of Impagidinium and Cordosphaeridium inodes minimus, or their absence, indicate environmental shifts. This shift reflects a transition from a neritic environment (Aïn Grab Formation) to an oceanic one (Mahmoud Formation). The Saouaf Formation is marked by a eustatic drop at its base (Unit I). However, Units II and III are defined by eustatic rises in pulsations. The Somaa sands were deposited in a neritic and/or epicontinental environment, followed by a return to an oceanic setting (Melquart Formation).

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引用次数: 0