Marine Micropaleontology最新文献_第4页

Foraminiferal image classification based on convolutional neural network considering data augmentation optimization 考虑数据增强优化的卷积神经网络有孔虫图像分类

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-06-06 DOI: 10.1016/j.marmicro.2025.102476

Jincan Wang , Muhui Zhang , Weiping Zeng , Songzhu Gu , Qingzhong Liang , Shuqin Zhou , Zimeng Gao

Foraminifera are of utmost importance in paleoclimate and marine ecosystem research, with accurate classification being equally vital. Convolutional Neural Networks (CNNs) can realize the automatic classification of foraminiferal images, but they usually rely on data augmentation to address the issue of data scarcity. Despite the widespread use of data augmentation methods, the impacts of various augmentation methods on the classification of foraminifera remain unclear. In this study, we systematically evaluated the effects of different data augmentation methods on the classification performance of CNNs using three publicly available datasets. Experiments based on the ResNet-50 architecture showed that random rotation (RR), random flipping (RF), and random erasing (RE, ratio = 0.2) significantly improved the classification accuracy. The combined model of these three methods achieved accuracies of 89.4 %, 89.7 %, and 95.7 %, and F1 scores of 72.7 %, 72.8 %, and 84.3 % in the three tasks respectively. Compared with the basic model, the accuracy (A) increased by an average of 3.2 %, and the F1 score (F1) increased by an average of 7.1 %. This study confirms that selecting and combining appropriate data augmentation methods can effectively enhance the performance of foraminiferal image classification, with the combination of RR, RF, and RE being the most effective.

有孔虫在古气候和海洋生态系统研究中具有极其重要的意义，准确的分类同样至关重要。卷积神经网络（cnn）可以实现有孔虫图像的自动分类，但通常依赖于数据增强来解决数据稀缺性问题。尽管数据增强方法被广泛使用，但各种增强方法对有孔虫分类的影响尚不清楚。在这项研究中，我们使用三个公开的数据集系统地评估了不同的数据增强方法对cnn分类性能的影响。基于ResNet-50架构的实验表明，随机旋转（RR）、随机翻转（RF）和随机擦除（RE, ratio = 0.2）显著提高了分类精度。三种方法组合模型的准确率分别为89.4%、89.7%和95.7%，F1得分分别为72.7%、72.8%和84.3%。与基本模型相比，准确率(A)平均提高3.2%，F1分数（F1）平均提高7.1%。本研究证实，选择和组合合适的数据增强方法可以有效提高有孔虫图像分类的性能，其中RR、RF和RE的组合效果最好。

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引用次数: 0

Environmental history of northwestern Vancouver Island (British Columbia, Canada) during the Holocene: A high-resolution dinoflagellate cyst record from Kyuquot Sound 加拿大不列颠哥伦比亚省温哥华岛西北部全新世环境史：奎括湾高分辨率鞭毛藻囊记录

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-06-02 DOI: 10.1016/j.marmicro.2025.102475

Pieter R. Gurdebeke , Vera Pospelova , Kenneth N. Mertens , Zhen Li , Bjarn Van Riet , Audrey Dallimore , Stephen Louwye

Environmental changes over the Holocene were reconstructed based on the analysis of dinoflagellate cyst assemblages, their absolute abundances, and morphological changes in Operculodinium centrocarpum sensu Wall & Dale 1966 from 103 sediment samples collected from Core 2012002PGC133 in Tahsish Inlet (Kyuquot Sound), a fjord on the west coast of Vancouver Island (British Columbia, Canada). Eight accelerator mass spectrometry ¹⁴C dates indicate that the record spans the last 12 ka. The cysts are well-preserved, with assemblages displaying high diversity (37 taxa). Six dinoflagellate cyst assemblage zones were identified. Zone I is dominated by Operculodinium centrocarpum sensu Wall & Dale 1966, while subsequent zones (II–IV) are characterized mainly by cysts of heterotrophic species. The uppermost zones (V–VI) show increased abundances of autotrophic taxa. The dinoflagellate cyst record reflects regional and global environmental signals. The dominance of Operculodinium centrocarpum sensu Wall & Dale 1966 during the Younger Dryas corresponds to a lower relative sea level, indicative of marsh-like conditions or proximity to the inlet head at the core site. Increased heterotrophic taxa during the late Early and Middle Holocene suggests a rising marine influence due to RSL rise, possibly enhancing primary productivity through coastal upwelling. Reduced process lengths in Operculodinium centrocarpum sensu Wall & Dale 1966 around ∼8.7 cal kyr BP indicate an abrupt change in local environmental conditions. A sharp increase in absolute cyst abundances ∼2.2 cal kyr BP, primarily driven by Spiniferites spp., is proposed to be linked with climate- and tsunami-related mechanisms.

本文通过对全壳鞭毛藻囊群、绝对丰度和形态变化的分析，重建了全新世的环境变化。从温哥华岛（加拿大不列颠哥伦比亚省）西海岸的一个峡湾tahish Inlet （Kyuquot Sound）收集的103个沉积物样本中提取了Dale 1966。8个加速器质谱14C测年表明该记录跨越了过去12 ka。包囊保存完好，组合多样性高（37个分类群）。发现了6个鞭毛藻包囊聚集带。第I区以中心果壳菌（Operculodinium centrrocarpum sensu Wall）为主；Dale 1966，而随后的区域（II-IV）主要以异养物种的囊肿为特征。最上层（V-VI）自养类群的丰度增加。鞭毛藻囊肿记录反映了区域和全球的环境信号。中心果壳菌的优势性研究新仙女木期的1966谷对应于相对较低的海平面，表明类似沼泽的条件或靠近核心位置的入口头。早全新世晚期和中全新世异养分类群的增加表明，由于RSL上升，海洋的影响增加，可能通过沿海上升流提高初级生产力。缩短了花椒的加工长度；Dale 1966年约8.7 cal kyr BP表明当地环境条件发生了突变。大约2.2 cal kyr BP的绝对囊肿丰度的急剧增加，主要是由Spiniferites spp驱动的，被认为与气候和海啸相关机制有关。

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引用次数: 0

Sedimentary record of Polysphaeridium zoharyi (cyst of Pyrodinium bahamense) in El Colorado Lagoon, Gulf of California 加利福尼亚湾El Colorado泻湖Polysphaeridium zoharyi （Pyrodinium bahamense囊肿）的沉积记录

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-05-21 DOI: 10.1016/j.marmicro.2025.102472

Tomasa Cuellar-Martinez, Rosalba Alonso-Rodríguez, Ana Carolina Ruiz-Fernández, Joan-Albert Sanchez-Cabeza

The temporal variations in abundances (cyst g⁻¹ and percentages) and fluxes (cyst cm⁻² yr⁻¹) of dinoflagellate cysts, including Polysphaeridium zoharyi from the toxic species Pyrodinium bahamense, were analyzed in a ²¹⁰Pb-dated sediment core from El Colorado Lagoon (Mexico) to investigate potential natural and/or human-driven factors, influencing the proliferation of P. bahamense, by examining the relationship between P. zoharyi abundance and geochemical indicators of sediment provenance and hydrodynamic conditions. P. zoharyi was the most abundant and frequently observed species along the core. The dominance of P. zoharyi was linked to the prevalence of terrigenous influence in most core sections, implying enhanced nutrient delivery. In recent years (∼1970s), the decrease in P. zoharyi percentages was associated with a local shift in hydrodynamic conditions, as revealed by an increase in sand content, changes in the δ¹³C and δ¹⁵N composition, and higher concentrations of marine indicator elements (Br, Ca, Na, and Sr). The change in hydrodynamic conditions suggests enhanced connectivity with the sea, likely triggered by a meteorological event. We highlight the importance of integrating multiple geochemical proxies with cyst analysis to assess changes in species assemblages and how local conditions, such as shifts in hydrodynamic conditions, that can influence species composition. This study contributes to paleoecology and phytoplankton ecology by documenting species responses to natural and anthropogenic disturbances. It confirms the recurrence and dominance of P. bahamense cysts, a toxin-producing species associated with harmful algal blooms. The findings underscore the need for continued monitoring, contingency planning, and water quality protection in coastal ecosystems.

在El Colorado Lagoon（墨西哥）的210pb年代沉积物岩心中分析了鞭毛藻包囊的丰度（包囊g−1和百分比）和通量（包囊cm−2 yr−1）的时间变化，以研究影响P. bahamense增殖的潜在自然和/或人为驱动因素，其中包括有毒物种Pyrodinium bahamense的Polysphaeridium zoharyi。通过研究佐哈氏藻丰度与沉积物物源地球化学指标和水动力条件的关系。沿岩心分布最丰富、最常被观测到的物种为佐哈依（P. zoharyi）。P. zoharyi的优势与大多数核心部分普遍存在陆源影响有关，这意味着营养输送增强。近年来（~ 20世纪70年代），沙含量的增加、δ13C和δ15N组成的变化以及海洋指示元素（Br、Ca、Na和Sr）浓度的升高表明，zoharyi P.百分比的下降与局部水动力条件的变化有关。水动力条件的变化表明，与海洋的联系增强了，这可能是由气象事件引发的。我们强调了将多种地球化学指标与囊肿分析相结合的重要性，以评估物种组合的变化以及当地条件（如水动力条件的变化）如何影响物种组成。该研究通过记录物种对自然和人为干扰的响应，为古生态学和浮游植物生态学做出贡献。它证实了P. bahamense囊肿的复发和优势，P. bahamense囊肿是一种与有害藻华有关的产毒物种。研究结果强调了在沿海生态系统中持续监测、应急计划和水质保护的必要性。

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引用次数: 0

The genetic isolation of planktonic foraminifera in the North Pacific gyre and adjacent marginal seas 北太平洋环流及其邻近边缘海浮游有孔虫的遗传分离

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-05-21 DOI: 10.1016/j.marmicro.2025.102473

Kate F. Darling , Agnes K.M. Weiner , Atsushi Kurasawa , Takashi Toyofuku , Hiroshi Nishi , Hiroshi Kitazato

Gaining insight into the speciation processes prevailing in the modern open ocean requires a comprehensive understanding of the spatial dynamics of the planktonic species that inhabit it, calibrated against time. The high-resolution fossil record of the planktonic foraminifera not only provides such insight but also plays a crucial role in the study of past climate. Both rely on understanding how species relate to the current physical and ecological character of the oceanic water masses they inhabit. Within global single cell barcoding and metabarcoding studies of planktonic foraminifera, the North Pacific subtropical and subpolar gyres remain under-sampled, with the capacity to harbour unrecognised ecologically distinct cryptic species. Targeting this issue, Globigerina bulloides specimens were collected during 12 cruises and near shore sampling campaigns throughout the Northern Pacific and marginal seas. Using standard molecular approaches, 406 specimens were genetically characterised and combined with 42 publicly available sequences to provide a fully comprehensive overview of G. bulloides diversity throughout the North Pacific. Of ten globally recognised genotypes, six (Ia, Ic, Id, IIa, IId, IIf) inhabit the water masses south of the Subpolar Front, with only a single genotype (IIe) inhabiting the vast Subpolar gyre and marginal seas. Genetic isolation was found to prevail throughout both the western subtropical waters (Types Ic and Id) and subpolar waters (Type IIe) of the North Pacific together with the North and South Pacific eastern boundary currents (Type IId). Unlike the Atlantic, bipolarity does not occur between the North Pacific and the Southern Ocean subpolar/polar pelagic biomes.

要深入了解现代开放海洋中普遍存在的物种形成过程，需要对栖息在其中的浮游生物物种的空间动态有全面的了解，并根据时间进行校准。浮游有孔虫的高分辨率化石记录不仅提供了这样的见解，而且在研究过去的气候中起着至关重要的作用。两者都依赖于了解物种与它们所栖息的海洋水体当前的物理和生态特征之间的关系。在全球浮游有孔虫单细胞条形码和超条形码研究中，北太平洋亚热带和亚极地环流的样本仍然不足，有能力庇护未被识别的生态独特的隐物种。针对这一问题，在整个北太平洋和边缘海域进行了12次巡航和近岸取样活动，收集了球形球虫标本。使用标准的分子方法，对406个标本进行了遗传表征，并与42个公开的序列相结合，以提供整个北太平洋G. bulloides多样性的全面概述。在全球公认的十种基因型中，有六种（Ia、Ic、Id、IIa、IId、IIf）生活在亚极锋以南的水团中，只有一种基因型（IIe）生活在广阔的亚极环流和边缘海域。遗传隔离现象普遍存在于西亚热带水域（Ic型和Id型）和北太平洋亚极地水域（IIe型）以及南北太平洋东部边界流（IId型）。与大西洋不同的是，在北太平洋和南大洋的亚极地/极地远洋生物群系之间不会出现双极性。

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引用次数: 0

Extant benthic foraminifera from the Indonesian seas: An update of what we know so far and implications for future studies 印度尼西亚海域现存底栖有孔虫：迄今为止我们所知道的最新情况及其对未来研究的影响

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-05-01 DOI: 10.1016/j.marmicro.2025.102471

Sinatrya D. Prayudi , Suhartati M. Natsir , Michael A. Kaminski

To offer a comprehensive understanding of the diversity of benthic foraminifera in the Indonesian seas, we analyzed more than 70 years of datasets from both local and international sources. By reviewing articles covering three major biogeographical regions—Sunda Shelf, Sahul Shelf, and Wallacea—and their varying environmental conditions and depositional environments, we identified a total of 1164 species (including uncertain and genus-level identifications) belonging to 448 genera, 136 families, 14 orders, and four classes, in addition to 1116 genus-level naming (sp. and spp.). Our analysis also revealed 762 instances of taxonomic misnaming, with errors stemming from the use of unaccepted names and confusion between fossils, planktonic, and benthic assemblages. Additionally, most of the reviewed studies were found to be incomplete due to insufficient oceanographic data and a lack of detailed species counts, despite the importance of these factors in such research. This work establishes a robust baseline for future studies and highlights key issues that need to be addressed to avoid repeating past uncertainties and to promote more focused research on benthic foraminifera in the region.

为了全面了解印度尼西亚海域底栖有孔虫的多样性，我们分析了70多年来来自当地和国际来源的数据集。通过对sunda陆架、Sahul陆架和wallea陆架三个主要生物地理区域及其不同的环境条件和沉积环境的文献回顾，我们共鉴定出448属、136科、14目、4纲的1164种（包括不确定和属级鉴定），以及1116种属级命名（sp.和spp.）。我们的分析还揭示了762个分类命名错误的例子，这些错误源于使用不被接受的名称以及化石、浮游生物和底栖生物组合之间的混淆。此外，尽管这些因素在此类研究中很重要，但由于海洋学数据不足和缺乏详细的物种计数，大多数审查的研究发现是不完整的。这项工作为未来的研究奠定了坚实的基础，并强调了需要解决的关键问题，以避免重复过去的不确定性，并促进对该地区底栖有孔虫的更集中的研究。

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引用次数: 0

Early impacts of Arctic amplification in the western North Water Polynya: A 400-year perspective 北极放大对北水峡西部的早期影响：400年的视角

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-05-01 DOI: 10.1016/j.marmicro.2025.102470

Kelsey A. Koerner , Audrey Limoges , Emily Pike-Connolly , Nicolas Van Nieuwenhove , André Rochon

The North Water (NOW) polynya in northern Baffin Bay is known for persistent open water, attracting marine mammals and birds during winter. Ice bridges forming north of the NOW at constriction points in Nares Strait aid in sustaining these open water conditions. However, Arctic Amplification has weakened these ice bridges, altering water and sea ice flow into the NOW. We examined the effect of climate warming and recent ice bridge failures through 400 years of changes in the western NOW. We analyzed dinoflagellate cyst (dinocyst) assemblages in a surface sediment transect across the NOW to assess their distribution as indicators of surface water masses. We then analyzed dinocysts and geochemical proxies (carbon and nitrogen signatures) from two sediment cores in the western NOW. Results show the eastern NOW, influenced by the West Greenland Current (WGC), exhibits higher contributions of mixotrophic taxa and total dinocyst concentrations than the western region, influenced by Arctic water outflow. Sediment cores show a 300-year period of stability in the western NOW (1620–1920 CE), followed by an increase in mixotrophic taxa and total dinocyst fluxes, predating observed ice bridge failures. Around 1980 CE, higher abundances of Operculodinium centrocarpum, and cysts of Polarella glacialis and Pentapharsodinium dalei, suggest early sea ice retreat, seemingly attributable to increased WGC influence. These findings demonstrate the early impact of Arctic Amplification on the NOW, with significant changes starting in the first half of the 20th century, which contribute to understanding the timing and propagation of oceanographic changes in the polynya.

巴芬湾北部的北水多冰湖（NOW）以持续开放的水域而闻名，在冬季吸引了海洋哺乳动物和鸟类。现在在Nares海峡的收缩点以北形成的冰桥有助于维持这些开放的水域条件。然而，北极放大削弱了这些冰桥，改变了流入现在的水和海冰。我们通过400年的变化研究了气候变暖和最近冰桥坍塌对西部NOW的影响。我们分析了横跨NOW的表层沉积物样带中的鞭毛藻囊（dinocyst）组合，以评估它们作为地表水质量指标的分布。然后，我们分析了现在西部两个沉积物岩心的生物囊和地球化学指标（碳和氮特征）。结果表明，受西格陵兰洋流影响的东部NOW区混合营养类群和总dinocyst浓度的贡献高于受北极水流影响的西部地区。沉积物岩心显示，现在西部（公元1620-1920年）有300年的稳定期，随后混合营养分类群和总生物囊通量增加，早于观测到的冰桥破坏。1980年前后，Operculodinium centrrocarpum的丰度较高，Polarella glacalis和Pentapharsodinium dalei的囊泡也较高，表明早期海冰退缩，似乎可归因于WGC影响的增加。这些发现证明了北极放大对现在的早期影响，其显著变化始于20世纪上半叶，这有助于理解冰湖海洋变化的时间和传播。

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引用次数: 0

Deep-sea benthic foraminifera respond to rapid environmental changes in the central Red Sea during the last glacial period 末次冰期红海中部深海底栖有孔虫对快速环境变化的响应

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-05-01 DOI: 10.1016/j.marmicro.2025.102474

Raphaël Hubert-Huard , Yvonne Milker , Gerhard Schmiedl

This study investigates the response of deep-sea benthic foraminifera to changes in food fluxes and dissolved bottom water oxygen in the central Red Sea during the last glacial period (Marine Isotope Stages (MIS) 3 and 4). To assess variations in nutrient intrusion from the Arabian Sea and regional organic matter fluxes, we developed the Red Sea Productivity Index (RSPI) based on changes in sea level and African-Arabian monsoon intensity. We found four distinct species groups, each reflecting different ecological niches and opportunistic behavior. Overall, the fauna of MIS 3 is dominated by the generalist species Bolivina subreticulata, which co-occurs or alternates with other preferentially infaunal taxa of varying opportunistic responses. Changes in the dominance of the different species are primarily controlled by seasonal productivity and associated quantity and quality of available organic matter at the sea floor. This is reflected by a close correspondence of the RSPI and a succession of infaunal species, including Uvigerina juncea s.l., and Bolivina variabilis as the most opportunistic taxa, adapted to strong seasonal food pulses. The succession of the species groups are influenced by millennial-scale changes of the African-Arabian monsoon system and Red Sea deep-water ventilation. This suggests a close link to both low- and high-latitude Northern Hemisphere climate variability. Changes in glacial deep-water oxygenation seem to play an important role during MIS 4, when the dominance of Bolivina persiensis indicates a vertical expansion of the oxygen minimum zone. The high glacial deep-water salinities during sea-level lowstands also fostered the occurrence of miliolid taxa.

本文研究了末次冰期红海中部深海底栖有孔虫对食物通量和溶解氧变化的响应（海洋同位素阶段（MIS） 3和4）。为了评估来自阿拉伯海的养分入侵和区域有机质通量的变化，我们基于海平面和非洲-阿拉伯季风强度的变化建立了红海生产力指数（RSPI）。我们发现了四个不同的物种群体，每个群体都反映了不同的生态位和机会主义行为。总体而言，MIS 3区系以多面手物种Bolivina subreticulata为主，与其他具有不同机会性反应的优先动物类群共存或交替存在。不同物种优势地位的变化主要受季节生产力和海底可利用有机质的相关数量和质量的控制。这反映在RSPI与一系列水生物种的密切对应关系上，包括Uvigerina juncea s.l.和Bolivina variabilis作为最具机会主义的分类群，适应强烈的季节性食物脉冲。物种群的演替受非洲-阿拉伯季风系统的千年尺度变化和红海深水通风的影响。这表明与北半球低纬度和高纬度气候变化有密切联系。冰川深水氧合的变化似乎在MIS 4期间发挥了重要作用，当Bolivina persiensis的优势表明氧最小带的垂直扩展时。在海平面低洼时，高的冰川深水盐度也促进了百万生物类群的发生。

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引用次数: 0

Benthic ostracods as environmental proxies in Nile Delta Coastal Lagoon 尼罗河三角洲沿海泻湖底栖介形类环境指标研究

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-04-23 DOI: 10.1016/j.marmicro.2025.102469

Sherif M. El Baz , Abd-ElMonsef A. El-Badry , Pamela Hallock , Ahmed M. BadrElDin

The coastal Nile Delta wetlands are essential in the protection of the cultivated deltaic land against sea level rise and are major resources for biodiversity and fisheries productivity. The Manzala Lagoon ranks highly polluted among the lacustrine coastal environments of the Nile Delta of Egypt. The environmental quality of the lagoon plummeted a few decades ago with the increase in massive quantities of untreated mixed discharges (agricultural, industrial, and municipal). To evaluate the environmental status of the lagoon requires both geochemical analyses and bioindicators. Total organic carbon and concentrations of seven potentially toxic elements (Pb, Cu, Cd, Zn, Ni, Co, Fe) were determined in 25 sediment samples collected during summer 2014, from which three pollution indices were calculated (Contamination Factor, Degree of Contamination, and Pollution Loading Index). In addition, ostracod assemblages were assessed in the very-fine and fine sand-size fractions of the sediments. The lagoonal environment is characterized by low total dissolved solids, abundant organic matter, heavy metal contamination by Pb, Co, Ni, and especially Cd, and low diversity ostracod assemblages. Six fresh- and brackish water ostracod species were documented, but the assemblage was overwhelmingly dominated (>98 %) by stress-tolerant Cyprideis torosa. While this species correlated strongly with total dissolved solids and fine sediment textures, overall, the limited ostracod diversity and dominance of a stress-tolerant species reflects the compromised ecological quality of Manzala Lagoon.

尼罗河三角洲沿海湿地对于保护三角洲耕地免受海平面上升的影响至关重要，也是生物多样性和渔业生产力的主要资源。Manzala泻湖在埃及尼罗河三角洲的湖泊沿岸环境中污染严重。几十年前，随着大量未经处理的混合排放物（农业、工业和市政）的增加，泻湖的环境质量急剧下降。评价泻湖的环境状况需要地球化学分析和生物指标。测定了2014年夏季采集的25份沉积物样品的总有机碳和7种潜在有毒元素（Pb、Cu、Cd、Zn、Ni、Co、Fe）浓度，并计算了污染系数、污染程度和污染负荷指数3个污染指标。此外，在沉积物的极细和细砂级组分中评估介形虫组合。泻湖环境具有总溶解固形物少、有机质丰富、重金属受Pb、Co、Ni、特别是Cd污染、介形虫组合多样性低的特点。记录了6种淡水和半咸水介形类，但该组合绝大多数（> 98%）为耐应力的扁扁螺（cydeis torosa）。虽然该物种与总溶解固体和细沉积物结构密切相关，但总体而言，有限的介形虫多样性和耐应力物种的优势反映了Manzala泻湖生态质量的下降。

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引用次数: 0

Ostracod and foraminiferal assemblages in Tébessa (Northeast Algeria): Insights into Santonian cooling effects Tébessa（阿尔及利亚东北部）的底栖动物和有孔虫组合：洞察桑顿纪的冷却效应

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-04-14 DOI: 10.1016/j.marmicro.2025.102468

Sakina Nemouchi , Sihem Salmi-Laouar , Ahmed Awad Abdelhady , Amor Deghaichia , Mostafa M. Sayed , Youssef Bazeen , Michael Hesemann , Mohamed Ahmed , Mabrouk Boughdiri

A well-exposed Coniacian-Santonian stratigraphic section in the Bir Mokadam Mountains, west of Tébessa (Algeria), was investigated through biostratigraphic and paleoenvironmental analyses focusing on planktic foraminifera and ostracods, respectively. The studied interval encompasses deposits from the Essen Formation, consisting predominantly of clayey marls. A total of 318 samples were collected and examined, leading to the identification of 26 planktic foraminiferal species distributed across 11 genera. The Coniacian is characterized by the presence of the Dicarinella primitiva and Marginotruncana sinuosa biozones, whereas the Santonian is distinguished by Sigalia carpatica, Dicarinella asymetrica, and Globotruncanita elevata biozones. The quantitative analyses revealed significant differences between the Coniacian and Santonian stages. The Coniacian and the lower parts of the Santonian exhibit higher diversity, characterized by a greater abundance of smooth ostracods, keeled and globular foraminifera. In contrast, the upper part of the Santonian is marked by a notable decrease in diversity and an increase in dominance of the ostracods and the also the planktonic foraminifera, indicating a less balanced ecological structure. The decline in diversity is herein tentatively attributed to a climate cooling and/or bottom-water minor dysoxia. Notably, there is a negative relationship between ostracod and foraminiferal abundances, the cause of which remains unclear and requires further investigations.

通过生物地层学和古环境分析，研究了阿尔及利亚tsamuessa西部Bir Mokadam山脉的coniian - santonian地层剖面，研究了浮游有孔虫和介形虫。研究的层段包括埃森组的沉积物，主要由粘土泥灰岩组成。共采集318份样本，鉴定出浮游有孔虫26种，分属11属。Coniacian以Dicarinella primitiva和Marginotruncana sinuosa生物带为特征，而san antonian则以Sigalia carpatica、Dicarinella asymetrica和Globotruncanita elevata生物带为特征。定量分析表明，康尼亚纪和圣东纪之间存在显著差异。Coniacian和Santonian的下部表现出较高的多样性，以光滑介形虫、龙骨虫和球状有孔虫为特征。而在三东统上部，介形类和浮游有孔虫的多样性明显减少，优势度明显增加，生态结构不平衡。多样性的减少暂时归因于气候变冷和/或底水轻度缺氧。值得注意的是，介形类和有孔虫丰度之间存在负相关关系，其原因尚不清楚，需要进一步调查。

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Are there marine sedimentary losses and transgressions in the Southeast Bohai Sea during MIS 2-MIS 3? 2- 3期渤海东南部是否存在海相沉积损失和海侵？

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.

渤海浅海陆架区以海侵-回归旋回为主的沉积构型包含了全球海平面、气候和局部构造的信息。然而，以往在轨道时间尺度上对该地区早更新世的海侵-回归旋回的研究很少。本文对渤海32.49 m (93kyr BP) HZK02岩心进行了沉积学、古生物学综合研究，建立了AMS 14C和5个OSL年龄模型。与以往渤海地区花粉研究结果进行比较，结果表明，渤海地区在5 - 5层发生了两次显著的海侵，即2层顶部和1层上部，有大量来自陆架近岸浅海的有孔虫，与以松属和栎属为主的乔木花粉相对应。而在海平面显著下降的MIS 4、MIS 5b等较冷时期，陆生草本植物以蒿属和藜科植物为主，对应于MIS 5b、MIS 5a、MIS 4和MIS 3等陆生沉积层中有孔虫的稀少。研究发现，在8.18 ~ 6.10 m深度，仅2.08 m深度，沉积速率非常高，持续时间从6.41万~ 1.05万yr BP，这可能是MIS 3和MIS 2沉积缺失的原因。海侵信号主要出现在2号沉积物的上部，3号沉积物几乎没有海侵信号。

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