Marine Micropaleontology最新文献_第6页

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 : 2025-05-01 Epub 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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引用次数: 0

Siliceous plankton flux and radiolarian community structure in the highly oligotrophic Ionian Sea (Eastern Mediterranean) – Imprints of climate variability 高度寡营养伊奥尼亚海（东地中海）硅质浮游生物通量和放射虫群落结构——气候变率的印记

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-04-01 Epub 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.

本研究基于在富营养化的南爱奥尼亚海（Nestor站点）700 m深度收集的沉积物捕集器材料，首次探讨了季节和多年（2015-2017）气候变化对东地中海硅质浮游生物通量和放射虫群落结构在物种水平的影响。共鉴定出143个放射虫分类群，大部分在种水平。幼虫占放射虫总通量的35 - 70%。鉴定出39个硅藻类群，包括一些淡水种类。放射虫和硅藻与有机碳、蛋白石和总质量通量一致，在季节通量变化中表现出相当相似的模式，包括两个季节性高峰。第一次记录于2015年冬末（2月下旬）；认为这是冬末水柱混合加剧的结果。硅质浮游生物通量的第二个高峰出现在2015年和2017年夏末至初秋（8 - 9月）。这一峰值被解释为佩洛普斯反气旋环流影响减弱后局部上升流事件的结果。第三次生产力事件发生在2016年4月和5月，被解释为受到北非沙尘沉积的影响。尽管我们的沉积物捕集器数据系列不完整，但我们的数据集是有价值的，因为它是有史以来第一次对地中海多胱氨酸放射虫垂直出口率进行物种水平的研究，并结合了对地中海硅质动物园和浮游植物通量的时间动态的见解。

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引用次数: 0

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 : 2025-04-01 Epub 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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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) 钙质纳米化石Reticulofenestra oamaruensis的系统进化：南太平洋IODP U1553遗址微进化的一个例子

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-04-01 Epub 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.

南大洋（Campbell高原）的IODP 378远征队在U1553遗址恢复了一个古近系沉积剖面，该剖面在晚始新世-早渐新世区间通过多个孔（a - E）取心。地层连续性和保存良好的钙质纳米化石为研究南大洋始新世/渐新世过渡（EOT）的生物地层标志Reticulofenestra oamaruensis的种系起源提供了机会。通过对奥马鲁河鼠及其近缘种克拉特拉网（Reticulofenestra clatrata）的生物特征和形态分析，揭示了克拉特拉鼠与奥马鲁河鼠之间的中间形态。这些过渡形态被标记为Reticulofenestra过渡形态1 （R. t1）和Reticulofenestra过渡形态2 (R. t2)，它们与端元的大小不同，分别分为10-12 μm和12-14 μm两类。种内进化趋势显示，克拉特拉河鼠（R. clatrata）的尺寸逐渐增大（8 ~ 10 μm），经过以R. t1和R. t2为代表的中间步骤，最终形成oamaruensis（≥14 μm）。这两种形态都被纳入到R. oamaruensis的物种鉴定中，并在连续的层次上进入地层记录，从而划定了一个在SO生物地层学中有用的“谱系带”。在始新世/渐新世界线附近，克拉特拉河鼠和中大型奥马鲁河鼠消失。基于形态同源性、从克拉特拉河鼠到奥马鲁拉河鼠的逐渐增大的大小趋势、地层范围的连续性和相同的地理分布，我们发现了一种南方高纬度特有的种系菌株，其中克拉特拉河鼠为原型。

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引用次数: 0

Orbital-scale biotic and paleoceanographic changes in Japan Sea during the late Miocene global cooling (LMGC) 晚中新世全球变冷（LMGC）期间日本海生物和古海洋学的轨道尺度变化

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-03-01 Epub 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.

晚中新世全球变冷；（约7.9-5.8 Ma）伴随着全球环境变化，包括季风强度、海洋环流和生物更替。最近的研究表明，日本海的环境和生物发生了剧烈的变化。日本海放射虫区系表明太平洋中部水（PCW）种三毛虫（Tricolocapsa papillosa）流入减少，亚北极种球形环虫（Cycladophora sphaeris）增加，特有优势放射虫中斑环虫（Cycladophora nakasekoi）灭绝。这些放射虫通量显示约100 kyr的偏心信号；然而，在LMGC期间，主要的古气候/古海洋信号似乎是~ 40-kyr的倾角旋回，这可能是由于采样分辨率较低而没有在放射虫通量中检测到。因此，这些放射虫通量的轨道尺度变化及其潜在的强迫机制仍不清楚。在这项研究中，我们以超过10年的分辨率建立了选定放射虫物种丰度的变化，并提出了在LMGC期间日本海古海洋学的斜向节奏变化。我们在大量的T. papillosa中检测到~ 40-kyr的旋回，这表明PCW流入日本海是由一个40-kyr的倾斜速度冰川旋回控制的。我们还在C. sphaeris丰度中检测到一个~ 40-kyr的信号，这意味着斜向冬季季风可能促进了亚北极水流入日本海。相反，C. nakasekoi丰度的变化缺乏~ 40-kyr信号。在中国湖泊沉积物的夏季风代用物中也观察到100 kyr的周期。因此，中色草有可能随着夏季风减弱而减少。

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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 来自移动基质的无孔有孔虫：隐藏的生物体和大错误-本质是肉眼看不到的

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-03-01 Epub 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.

在巴西东南部内陆大陆架进行的两个案例研究显示，附着在沉积物颗粒上或包裹在沉积物颗粒中的有孔虫的丰度和多样性出乎意料。样品用孟加拉玫瑰染色，用福尔马林固定，用三氯乙烯浮选分离游离有孔虫。筛选后，对残余部分进行了严格检查，发现了许多附着的个体和强大的凝集形式，这些凝集形式将沉积物颗粒纳入其测试中。该动物群包括很少在未固结的移动基质中记录的鲜为人知的属。浮动分数和剩余分数之间的比较揭示了显着的差异，强调当剩余分数被忽视时，对坚固和坚固形式的低估。正如稀薄曲线所示，忽略这些形式可能会损害环境和古环境的解释，特别是在高水动力区域，通常被视为动物群的挑战环境。本研究强调了将无孔有孔虫纳入动态海域生物多样性评估的重要性。我们为Murray（1973）的三元图提出了一个新的区域，即“高流体动力内海岸架”。此外，我们的研究结果表明，不适当的筛选方法可能会在分类记录中留下重大空白。许多附着有孔虫仍然是研究人员“看不见的眼睛”，往往是由于它们的形状，缺乏先验知识，或注意不足，导致低估了它们的密度和丰富程度。因此，这些生物在环境表征、分类记录，特别是在古生态学研究和监测工作中经常被忽视。

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引用次数: 0

Machine Learning for identification and classification of Foraminifera: Testing on monothalamids 有孔虫识别和分类的机器学习：单丘脑类的测试

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-03-01 Epub Date: 2025-01-18 DOI: 10.1016/j.marmicro.2025.102442

Anna Sabbatini , Francesca Caridi , Domenico Potena , Alessandra Negri

Here we propose an AI-based approach using machine learning (ML) to assist species identification and reduce morphotype redundancy in the study of monothalamous foraminifera. In fact, this group of protists, is often overlooked in taxonomic studies due to their morphological simplicity and diversity. These single-celled organisms with “soft” tests are poorly studied, with only a few species identified, while many morphotypes remain undescribed. Taxonomic research on monothalamids is limited by challenges in identification, lack of fossilization, and the time-intensive nature of the work. This gap may lead to underestimating biodiversity and hinder detecting ecosystem degradation. Despite these challenges, monothalamids play key roles in marine ecosystems, making their diversity crucial for conservation and resource management. With this in mind, we analyzed images from the scientific literature, extracting key morphological traits, such as chamber shape, shell type, composition, and aperture type, through objective human annotation to build a dataset processed by ML algorithms. Clustering techniques, such as K-Means, revealed that basic shape, followed by shell type and composition, were the primary features distinguishing clusters. This approach enabled more objective morphotype classification, improving consistency and reducing human bias.

These findings align with recent taxonomic revisions and demonstrate that applying unsupervised ML methods enhances species identification accuracy and streamlines the analysis of high-dimensional datasets.

在这里，我们提出了一种基于人工智能的方法，使用机器学习（ML）来帮助物种识别并减少单thalamous有孔虫研究中的形态冗余。事实上，这类原生生物由于其形态的简单和多样性，在分类学研究中经常被忽视。这些具有“软”测试的单细胞生物的研究很少，只有少数物种被确定，而许多形态仍然未被描述。单丘脑的分类学研究受到鉴定方面的挑战、缺乏化石和工作的时间密集性的限制。这一差距可能导致对生物多样性的低估，并阻碍对生态系统退化的检测。尽管存在这些挑战，单丘脑类在海洋生态系统中发挥着关键作用，使其多样性对养护和资源管理至关重要。考虑到这一点，我们分析了科学文献中的图像，通过客观的人工注释提取了关键的形态学特征，如腔室形状、壳类型、成分和孔径类型，构建了一个由ML算法处理的数据集。聚类技术，如K-Means，揭示了基本形状，其次是壳类型和组成，是区分聚类的主要特征。这种方法使形态学分类更加客观，提高了一致性，减少了人为偏见。这些发现与最近的分类学修订一致，并证明应用无监督机器学习方法可以提高物种识别的准确性，并简化高维数据集的分析。

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引用次数: 0

Morphometric analysis of coccolithophore genus Reticulofenestra: Insights into taxonomy and evolution during late Eocene to early Oligocene 网状球石藻属的形态测量学分析：始新世晚期至渐新世早期的分类与演化

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-03-01 Epub Date: 2025-01-10 DOI: 10.1016/j.marmicro.2024.102435

Ruigang Ma , David Bord , Xiaobo Jin , Chuanlian Liu

The coccolithophore Reticulofenestra is key to understanding late Cenozoic climate change, but taxonomic identification remains challenging. This study uses morphometric and mixture analysis to evaluate taxonomic criteria for late Eocene to early Oligocene Reticulofenestra. The method enables a systematic comparison between the taxonomic morphotypes and the components recognized through Gaussian mixture modeling of parameters of distal shield length, circularity, and central opening ratio. At the species level, a total of nine morphotypes were studied from 6700 data points collected across three study sites in the mid–low latitude Atlantic–Indian Oceans. The results demonstrate that length and circularity effectively distinguish groups, validating their uses as primary taxonomic criteria. Nevertheless, central opening ratio exhibits high intra–group variability, limiting its standalone application. In addition, our integrated data reveal three evolutionary phases: (1) initial diversification during late Eocene cooling; (2) extinction following peak diversity after the Eocene–Oligocene Transition; and (3) early Oligocene stabilization reflecting adaptation in smaller species. This work provides statistical references for the validation of semi-quantitative morphologic descriptions, which may help establish a robust framework for identifying this ecologically vital lineage and enhance our understanding of phytoplankton responses to past environmental changes. Future genomic studies will be crucial for elucidating genotype-phenotype-environment relationships in Reticulofenestra evolution.

球石藻Reticulofenestra是了解晚新生代气候变化的关键，但分类鉴定仍然具有挑战性。本研究采用形态计量学和混合分析方法，对晚始新世至早渐新世网状蕨的分类标准进行了评价。该方法能够将分类形态与通过远端屏蔽长度、圆度和中心开口比参数高斯混合建模识别的组分进行系统比较。在物种水平上，从中低纬度大西洋-印度洋三个研究地点收集的6700个数据点中，共研究了9种形态。结果表明，长度和圆度可以有效地区分类群，验证了它们作为主要分类标准的用途。然而，中心开孔率表现出较高的组内变异性，限制了其单独应用。此外，我们的综合数据揭示了三个演化阶段：(1)始新世晚期冷却时期的初始多样化；(2)始新世-渐新世过渡后的生物多样性高峰灭绝；(3)早渐新世稳定，反映了小物种的适应性。本研究为验证半定量的形态描述提供了统计参考，有助于建立一个强大的框架来识别这一生态重要的谱系，并增强我们对浮游植物对过去环境变化的响应的理解。未来的基因组研究将是阐明网纹蝶进化中基因型-表型-环境关系的关键。

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引用次数: 0

The biostratigraphy and palaeobiogeography of the Late Jurassic dinoflagellate cysts from the Binalud Mountains, NE Iran 伊朗东北部比纳鲁德山脉晚侏罗世甲藻囊的生物地层学和古生物地理

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-03-01 Epub 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.

本文研究了伊朗东北部特提斯西部比纳鲁德山脉达利柴组上部的鞭毛藻囊，该矿床主要由页岩和泥灰岩层组成。所分析的剖面产生了常见和多样的鞭毛藻囊组合，包括33属46种。这些组合与北半球晚侏罗世（晚牛津—晚铁桑世）dsj24—dsj33鞭毛藻囊带具有相关性。在这段时间内鉴定出的主要生物事件包括复合osphaeridium polonicum最后一次出现在牛津纪晚期，Ctenidodinium ornatum最后一次出现在牛津纪与kimmerid纪交界，Tubotuberella eisenackii和Scriniodinium crystallinum最后一次出现在kimmerid纪早期，Endoscrinium luridum最后一次出现在kimmerid纪与tithonian交界。鞭毛藻囊群与特提斯西部（中东、欧洲、北美东部和北非）的植物群具有很强的相似性，而与特提斯东部（澳大利亚、东亚和印度东北部）的同期植物群有显著差异，反映了晚侏罗世特提斯西部和东部之间的显著地方性差异。

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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 突尼斯海陆盆地中新世鞭毛藻囊的分布：古地理古生态重建与涨落运动

IF 1.5 4区地球科学 Q2 PALEONTOLOGY

Marine Micropaleontology

Pub Date : 2025-03-01 Epub 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).

突尼斯东北部和中东部中新世沉积主要为碎屑三角洲型。这些矿床被构造活动、地壳起伏和气候条件的变化组织成复杂的沉积序列。本研究介绍了中新世沉积物中提取的鞭毛藻囊群的演化。这些沉积物分布在1600万到530万年前。这些数据取自突尼斯东北部和中部的三个钻孔和三个区域。恐龙囊是气候变化和海平面波动的重要指标。他们的研究支持了从花粉粒分析中得到的结果。它揭示了这一时期的古生态、古地理和涨落情况。根据这些海洋微生物的生态偏好，建立了各种关联（海洋、浅海、气候等）。海洋环境的特点是含银的存在。浅海环境是由Cordosphaeridium inodes minimus的存在所定义的。同时，线虫和复盖虫对海洋环境具有浅海性。Lejeunecysta、opercullodinium、israelium、Polysphardium zoharyi、Homotryblium、Spiniferites、Cleistosphaeridium和Lingulodinium machaerophorum的丰度证实了这一点。这些结果与古水深测量和古地理相关的岩性和生物地层资料一致。恐龙囊分类群相对丰度的变化有助于追踪中新世期间海岸线的演变。Impagidinium和Cordosphaeridium inodes minimum相对丰度的变化或缺乏表明环境的变化。这种转变反映了从浅海环境（Aïn Grab组）到海洋环境（Mahmoud组）的转变。Saouaf组的特征是其底部（Unit I）的起伏下降。然而，Unit II和Unit III是由脉动的起伏上升所定义的。Somaa砂沉积在浅海和/或陆表环境中，随后返回到海洋环境（Melquart组）。

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引用次数: 0