Palaeogeography, Palaeoclimatology, Palaeoecology最新文献_第2页

The “Lochkovian-Pragian Event” re-assessed: New data from the low latitude shelf of peri-Gondwana 重新评估 "洛克维安-普拉格安事件"：来自近冈瓦纳低纬度大陆架的新数据

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-11-02 DOI: 10.1016/j.palaeo.2024.112580

Carlo Corradini , Maria G. Corriga , Monica Pondrelli , Amalia Spina , Thomas J. Suttner

In the late Lochkovian a regression is documented in several areas of the world, followed by a transgression in the early Pragian. Connected with the eustatic variation, a minor extinction event occurred (“Lochkovian-Pragian Event”), affecting several fossil groups, a strong reduction of carbonate production and sedimentary facies changes. The Carnic Alps are a key area for studying this event, because Lower Devonian rocks are widely exposed, representing diverse sedimentary environments from shallow water to relatively deep shelf. Fourteen sections were measured along the Carnic Alps across the Lochkovian-Pragian boundary. In the shallower part of the basin, both the Polinik and the Seekopf formations span the boundary, but evident erosional surfaces are observable in the field at the Lochkovian-Pragian boundary. Above the unconformity, at places the so-called megaclast horizon is present in the Seekopf Formation. In intermediate settings the Rauchkofel Fm. is unconfomably followed by the Kellerwand Fm., and different parts of the upper Lochkovian and lower Pragian are missing in the various sections. In the deeper parts of the basin the transition from the La Valute Fm. to the Findenig Fm. is slightly diachronous from the latest Lochkovian to the earliest Pragian; however, conodonts and tentaculitids are rare in the marly boundary beds, preventing a precise chronostratigraphic calibration of these levels. At places, evidence of subaerial exposure at the formational boundary is documented. In general, the hiatus seems to be larger in the western part of the Carnic Alps, in correspondence with the shallower parts of the succession, suggesting a sea level drop in the late Lochkovian, followed by a transgression in the Pragian. Data from the Carnic Alps are compared with those of other regions of North Gondwana to demonstrate that the sea-level variation at the Lochkovian-Pragian boundary are of global importance

据记载，在洛克维期晚期，世界多个地区出现了退缩，随后在普拉格期早期出现了横断。与震旦纪变迁相关联，发生了一次小规模的生物大灭绝事件（"洛克维期-普拉格期事件"），影响了多个化石群，碳酸盐生成量大幅减少，沉积面貌也发生了变化。卡尼阿尔卑斯山是研究这一事件的关键地区，因为下泥盆统岩石广泛出露，代表了从浅水到相对较深的陆架的各种沉积环境。我们沿卡尼阿尔卑斯山脉测量了 14 个横跨洛克维期-普拉格期边界的断面。在盆地较浅的地方，波利尼克地层和西科普夫地层都跨越了边界，但在洛可可维-普拉西边界的实地观察中，可以看到明显的侵蚀面。在不整合层之上，Seekopf 地层中有些地方出现了所谓的巨岩层。在中间地带，Rauchkofel 地层之后是 Kellerwand 地层，在不同的地段，上 Lochkovian 和下 Pragian 的不同部分缺失。在盆地较深的地方，从最晚的洛克维期到最早的普拉格期，从 La Valute Fm. 到 Findenig Fm. 的过渡略显不同步；然而，在泥灰质边界床中，锥齿类和触角类非常罕见，因此无法对这些层位进行精确的年代地层校准。在一些地方，有形成边界次生暴露的证据。总体而言，卡尼阿尔卑斯山西部的断裂似乎较大，与演替的较浅部分相对应，这表明海平面在洛克维期晚期下降，随后在普拉格期发生了横断。将卡尼阿尔卑斯山的数据与北冈瓦纳其他地区的数据进行了比较，以证明洛克维期-普拉格期边界的海平面变化具有全球重要性。

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引用次数: 0

Large and rapid salinity fluctuations affected the eastern Mediterranean at the Tortonian–Messinian transition 在托尔托尼-梅西尼过渡时期，地中海东部受到盐度快速大幅波动的影响

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-10-30 DOI: 10.1016/j.palaeo.2024.112568

Evangelia Besiou , Iuliana Vasiliev , George Kontakiotis , Konstantina Agiadi , Katharina Methner , Andreas Mulch , Wout Krijgsman , Assimina Antonarakou

Restricted marine basins are highly sensitive to climatic fluctuations, yet, paleoenvironmental responses to gateway restriction frequently remain unclear. Here, we investigate the Mediterranean Sea that experienced gradually restricted conditions starting during the late Tortonian and culminating with complete isolation from the Atlantic during the peak of the Messinian Salinity Crisis. We established sea surface temperature and salinity records during the Tortonian to Messinian transition (7.52–7.20 Ma) through coupled analysis of organic biomarkers and oxygen and carbon isotope ratios of planktonic foraminifera from the eastern Mediterranean basin (Potamida section, Crete Island, Greece). We further contrast these sea surface data with stable isotope records of benthonic foraminifera to identify periods of increased density-driven deterioration of bottom water ventilation in the basin. The combined results show that normal marine conditions, expressed by relatively warm (27.5 °C) Tortonian surface waters with normal salinity (38) prevailed until 7.36 Ma. The 7.36–7.32 Ma interval is characterized by pulses of increased bottom water salinity, that contrast the lasting normal salinity (39) at the sea surface, indicating strengthened water column stratification provoked by sluggish water circulation already prior to the Tortonian–Messinian boundary. A brief return to marine conditions, similar to the time prior to 7.36 Ma, re-appeared between 7.32 and 7.31 Ma. Between 7.31 and 7.28 Ma, a rebound to enhanced stratification took place accompanied by a high-amplitude, stepwise decrease in both sea surface temperature and sea surface salinity. Ultimately, the Tortonian–Messinian boundary was characterized by lower sea surface temperature and salinity accompanied by increased salinity and/or colder bottom waters. A ∼ 10 °C cooling episode (at 7.212 Ma) highlights the regional importance of the global Late Miocene cooling event.

受限的海洋盆地对气候波动高度敏感，然而，对门户受限的古环境反应往往仍不清楚。在此，我们对地中海进行了研究，该海域从托尔托尼晚期开始逐渐受到限制，最终在梅西尼盐度危机高峰期与大西洋完全隔绝。我们通过对地中海盆地东部（希腊克里特岛波塔米达断面）浮游有孔虫的有机生物标志物及氧和碳同位素比值的耦合分析，建立了托尔托尼至梅西尼过渡时期（7.52-7.20 Ma）的海面温度和盐度记录。我们进一步将这些海面数据与底栖有孔虫的稳定同位素记录进行对比，以确定该盆地底层水通气状况因密度增加而恶化的时期。综合结果表明，正常的海洋条件，即相对温暖（27.5 °C）、盐度正常（38）的托尔托尼亚表层海水，一直持续到 7.36 Ma。在 7.36-7.32 Ma 期间，底层水盐度呈脉冲式上升，与海面持久的正常盐度（39）形成鲜明对比，表明在托尔托尼-美西尼边界之前，由于水循环迟缓，水柱分层现象已经加强。在 7.32 至 7.31 Ma 之间，海洋条件短暂恢复，与 7.36 Ma 之前的情况相似。在 7.31 至 7.28 Ma 期间，伴随着海面温度和海面盐度的高振幅、阶梯式下降，出现了强化分层的反弹。最终，托尔托尼-梅西尼边界的特征是海面温度和盐度降低，同时盐度增加和/或底层水变冷。10 °C的降温事件（7.212 Ma）突出了全球晚中新世降温事件的区域重要性。

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引用次数: 0

Sediment source-to-sink patterns along the southeast China coast during the late Quaternary: New insights from sediment geochemistry and OSL ages in Ningde Bay 第四纪晚期中国东南沿海沉积物源-汇模式：宁德湾沉积物地球化学和OSL年龄的新见解

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-10-28 DOI: 10.1016/j.palaeo.2024.112577

Ping Liu , Jie Zhang , Yan Liu , Qianli Sun , Dan Zhang , Yue Li , Taoyuan Wei , Junjie Yu , Jilong Wang , Jing Chen

The geomorphology and environmental conditions of the southeast China coast are significantly influenced by sediment discharge from the Yangtze River, a major river located to the north. Nonetheless, the extent to which the Yangtze River affects sediment transport processes from source to sink along the southeast coast remains unclear. Our recent findings in coastal/marine deposits from the late Quaternary period (MIS5e, MIS3, and MIS1) in Ningde Bay offer new perspectives on this issue. Provenance discrimination of the late Quaternary boreholes was carried out using sediment geochemical analysis and OSL dating of fine- and medium-grained quartz. The results indicate varying provenances during sea-level fluctuation, with distal Yangtze River origins during MIS5e, MIS3, and MIS1, and a local source during MIS4. The findings also suggest that the southward transport of Yangtze sediments along the southeast China coast has occurred since MIS5e. However, OSL ages of the fine-grained quartz in the MIS3 deposit range from approximately 90 to 140 kyr, notably older than those of medium-grained quartz (40–80 kyr). This remarkable age discrepancy indicates that Yangtze-derived sediments previously deposited on the shelf of the East China Sea during MIS5 were reworked and transported southward in MIS3. This phenomenon can be elucidated by the insufficient supply of Yangtze sediments during MIS3, which could be linked to the weakened East Asian monsoon. This new source-to-sink pattern for the southeast China coast is characterized by a compensating mechanism of inner shelf old sediment in response to the inadequate supply of Yangtze sediments. This study contributes to a better understanding of the significant impacts of reduced Yangtze sediment input on its distal sedimentary systems over time.

中国东南沿海的地貌和环境条件受到长江这一北方大河泥沙排放的显著影响。然而，长江对东南沿海沉积物从源到汇的输移过程的影响程度仍不清楚。我们最近在宁德湾第四纪晚期（MIS5e、MIS3 和 MIS1）沿海/海洋沉积物中的发现为这一问题提供了新的视角。利用沉积物地球化学分析和细粒、中粒石英的 OSL 测年，对第四纪晚期钻孔进行了产地判别。结果表明，海平面波动期间的来源各不相同，在MIS5e、MIS3和MIS1期间来源于长江远端，而在MIS4期间来源于本地。研究结果还表明，自 MIS5e 以来，中国东南沿海的长江沉积物一直在向南迁移。然而，MIS3沉积中细粒石英的OSL年龄约为90-140 kyr，明显早于中粒石英（40-80 kyr）。这一明显的年龄差异表明，MIS5期间沉积在东海大陆架上的长江源沉积物在MIS3期间被重新加工并向南迁移。这一现象可解释为 MIS3 期间长江沉积物供应不足，这可能与东亚季风减弱有关。中国东南沿海这种新的源-汇模式的特点是内陆架老沉积物对长江沉积物供应不足的补偿机制。这项研究有助于更好地理解长江沉积物输入量减少对其远端沉积系统的重大影响。

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引用次数: 0

Using detrital zircon UPb geochronology to track the provenance of Miocene sediments in the northern Pearl River Mouth Basin, South China Sea 利用碎屑锆石UPb地质年代学追踪南海珠江口盆地北部中新世沉积物的出处

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-10-24 DOI: 10.1016/j.palaeo.2024.112567

Chang Zhong , Xiaoyin Tang , Xinyan Zhao , Shengbiao Hu

The Late Cenozoic provenance study of the Pearl River Mouth Basin (PRMB) holds significant implications for understanding the tectonic-climatic interactions, drainage evolution, and oceanic circulation in the northern South China Sea. However, the Miocene sediment routing system remains poorly understood due to the paucity of zircon geochronological data and the effects of sediment mixing and homogenization. This study reconstructs the ancient source-to-sink system by means of detrital zircon analyses from the northern PRMB and zircon age-based mixture modeling of well-defined provenance end-members. The results disclose varied and complex source-to-sink scenarios since the Early Miocene, involving three primary contributors: the Pearl River drainage system, coastal SE China, and Taiwan Island. In combination with seismic facies and climatic proxies, the intensive addition of Precambrian zircons suggests that, during the Middle and Late Miocene, progressive drainage expansion within the Yangtze Block likely contributed to the increasing sediment supply from the western Pearl River drainage system. Furthermore, the provenance shift in the northern PRMB, as indicated by the Mesozoic ages, may reflect a response to the activation of oceanic circulation and intensification of the East Asian monsoon. Additionally, though less significant, contributions from the Hainan and Luzon Island are also observed, indicating the input of the branch of the Kuroshio Current during the Late Miocene.

珠江口盆地晚新生代的成因研究对了解南海北部的构造-气候相互作用、排水演化和大洋环流具有重要意义。然而，由于锆石地质年代数据的缺乏以及沉积物混合和同质化的影响，人们对中新世沉积物溯源系统的了解仍然很有限。本研究通过对珠江口东岸北部的碎屑锆石进行分析，并对定义明确的来源末体进行基于锆石年龄的混合建模，重建了古老的源-汇系统。研究结果表明，自早中新世以来，从源到汇的情况复杂多样，主要涉及三个方面：珠江水系、中国东南沿海和台湾岛。结合地震剖面和气候代用指标，前寒武纪锆石的大量加入表明，在中新世中期和晚期，长江地块内逐渐扩大的排水范围很可能是珠江流域西部沉积物供应增加的原因。此外，中生代年龄所显示的珠江口北岸的产地变化可能反映了大洋环流的启动和东亚季风的加强。此外，还观察到海南岛和吕宋岛的贡献，虽然不那么重要，但也表明黑潮分支在晚中新世期间的输入。

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引用次数: 0

Timing and origin of the Lomagundi-Jatuli Event: Insights from UPb geochronology, C-O-Fe isotopes and REE compositions from the Jingshan Group, North China Craton 洛马昆迪-贾图里事件的时间和起源：来自华北克拉通京山群的UPb地质年代、C-O-Fe同位素和REE成分的启示

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-10-24 DOI: 10.1016/j.palaeo.2024.112574

Yuanlin Chen , Huan Li , Shangyi Gu , Gary G. Lash , Dadou Li , Chaoyang Zheng , Ligong Wang , Liu'an Duan

The Lomagundi-Jatuli Event (LJE) represents perhaps the largest and longest positive carbon isotope excursion of Earth history. However, the synchroneity, scale, and linkage of the LJE to Earth's early history of atmospheric oxygenation remain controversial. Strata of the Paleoproterozoic Jingshan Group of the North China Craton that preserve the isotopic record of the LJE excursion in marble layers and abundant graphite deposits provide an opportunity to elucidate the significance of the LJE. Carbon isotopic values (δ¹³C_V-PDB) of the LJE based on analysis of 20 samples of the Lugezhuang Formation, lower Jingshan Group, range from −0.8 to +9.6 ‰ and display positive co-variance with stable oxygen isotope values (δ¹⁸O_V-PDB). The positive carbon isotope excursion is constrained to 2140.6 ± 8.5 Ma (MSWD = 0.82, n = 25) based on magmatic zircon UPb geochronology of biotite granulite. Variation of facies-dependent carbon isotope values, the presence of graphite deposits of the Douya Formation, upper Jingshan Group, and the absence of a Ce anomaly in PAAS normalized REE patterns of marble samples suggest that the positive carbon isotope excursion is not linked to a marked increase of organic carbon burial and associated significant atmosphere oxygenation. Elevated concentrations of iron and PAAS-normalized middle REE enrichment of analyzed Jingshan Group marble samples point to anoxic and ferruginous oceanic conditions during accumulation of Jingshan Group carbonate. A positive Eu anomaly (average = 1.58), low La (average = 0.23), (Nd/Yb)_N (average = 1.27), and Y/Ho (average = 36.6) anomalies, and negative iron isotope values (average δ⁵⁶Fe = −0.12 ‰) are consistent with accumulation of Paleoproterozoic Jingshan Group carbonate in a restricted marine setting that was affected by high temperature hydrothermal fluids. Enrichment of the studied samples in heavy carbon isotope suggests elevated bio-productivity in the restricted, redox stratified marine setting in which Jingshan Group carbonate accumulated. Thus, it is likely that the positive stable carbon isotope excursion associated with Jingshan Group strata as well as other contemporaneous isotope excursions are local signals that are linked to a global perturbation of the carbon cycle.

Lomagundi-Jatuli 事件（LJE）可能是地球历史上规模最大、时间最长的碳同位素正偏移。然而，LJE 的同步性、规模以及与地球早期大气含氧历史的联系仍存在争议。华北克拉通古生代景山群地层中的大理岩层和丰富的石墨沉积中保存了 LJE 偏移的同位素记录，为阐明 LJE 的意义提供了机会。根据对京山下统鲁各庄组20个样品的分析，LJE的碳同位素值（δ13CV-PDB）在-0.8至+9.6‰之间，并与稳定氧同位素值（δ18OV-PDB）呈正共变关系。根据生物花岗岩的岩浆锆石UPb地质年代学，碳同位素的正偏移被限制在2140.6 ± 8.5 Ma (MSWD = 0.82, n = 25)。与岩相相关的碳同位素值的变化、京山组上统豆芽地层石墨沉积的存在以及大理岩样品的PAAS归一化REE模式中没有Ce异常，都表明碳同位素的正偏移与有机碳埋藏的明显增加以及相关的大气含氧量的显著增加无关。所分析的京山群大理岩样品中铁浓度的升高和PAAS归一化中REE的富集表明，在京山群碳酸盐岩堆积过程中存在缺氧和铁质海洋条件。正的Eu异常（平均=1.58），低的La（平均=0.23）、(Nd/Yb)N（平均=1.27）和Y/Ho（平均=36.6）异常，以及负的铁同位素值（平均δ56Fe=-0.12‰），都与古近纪京山群碳酸盐岩在受高温热液影响的限制性海洋环境中堆积一致。所研究样本重碳同位素的富集表明，京山群碳酸盐岩在受限的氧化还原分层海洋环境中的生物生产率较高。因此，与景山群地层相关的正稳定碳同位素偏移以及其他同期同位素偏移很可能是与全球碳循环扰动相关的局部信号。

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引用次数: 0

Linking the PETM and North Atlantic volcanism using tellurium in sediments 利用沉积物中的碲将 PETM 与北大西洋火山活动联系起来

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-10-24 DOI: 10.1016/j.palaeo.2024.112575

N.B. Baumann , M. Regelous , T. Adatte , N.R. Thibault , A. Regelous , B.P. Schultz , A. Fantasia , H. Madsen , K.M. Haase

The Paleocene – Eocene Thermal Maximum (PETM) was a short period (∼170 kyr) of global temperature rise starting at 55.93 Ma, which occurred during the breakup of the North Atlantic and the emplacement of the North Atlantic Igneous Province (NAIP). Recently, mercury (Hg) concentrations in sediments have been used in an attempt to connect the eruptive history of the NAIP with environmental change during this period, at a higher resolution than possible using geochronology. Here we present sedimentary tellurium (Te) as a novel proxy to further reconstruct NAIP volcanism at high resolution. We measured 45 trace elements in 401 sediment samples from 3 sections across the PETM in the northern hemisphere. All study sites exhibit an increase in Te concentrations and Te/Th ratios close to the onset of the PETM and remain high until the end of the main North Atlantic ash phase about 1 Myr later. The trace element data indicate that changes in sediment lithology or in environmental conditions do not influence sedimentary Te concentrations suggesting a volcanic source instead. We used existing age models to remove the effect of changes in sedimentation rate and calculated volcanic Te fluxes. Our Te data suggest increased volcanism in the latest Paleocene and early Eocene. This fits existing radiometric ages of the NAIP, which demonstrate that a more than 5 km thickness of lava in eastern Greenland and the Faroes was erupted within about 1 Myr between ∼56 to ∼55 Ma. All our study sites show similar Te flux variations across the PETM. In contrast, sedimentary mercury (Hg) profiles from these and other sites are less consistent. Tellurium in sediments may represent a useful proxy to reconstruct NAIP volcanism.

古新世-始新世热极盛期（PETM）是全球温度上升的一个短暂时期（∼170 kyr），始于 55.93 Ma，发生在北大西洋断裂和北大西洋火成岩带（NAIP）形成期间。最近，人们利用沉积物中的汞（Hg）浓度，试图将北大西洋火成岩带（NAIP）的喷发历史与这一时期的环境变化联系起来，其分辨率比地质年代学要高。在此，我们将沉积碲（Te）作为一种新的替代物，进一步以高分辨率重建 NAIP 火山活动。我们测量了北半球 PETM 3 个断面 401 个沉积物样本中的 45 种微量元素。所有研究地点的碲浓度和碲/钍比值在接近 PETM 开始时都有所上升，并在约 1 Myr 后的北大西洋主要火山灰阶段结束前一直保持较高水平。痕量元素数据表明，沉积物岩性或环境条件的变化并不影响沉积物中 Te 的浓度，这表明沉积物来源于火山。我们利用现有的年龄模型去除沉积速率变化的影响，并计算出火山Te通量。我们的 Te 数据表明，在古新世晚期和始新世早期，火山活动有所增加。这与 NAIP 现有的辐射年龄相吻合，后者表明格陵兰岛东部和法罗群岛超过 5 公里厚的熔岩是在∼56 至∼55 Ma 之间约 1 Myr 内喷发的。我们的所有研究地点在整个 PETM 期间都显示出类似的 Te 通量变化。相比之下，这些地点和其他地点的沉积汞（Hg）剖面则不太一致。沉积物中的碲可能是重建 NAIP 火山活动的有用替代物。

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引用次数: 0

Widespread coastal upwelling along the marginal Yangtze Platform (South China) during the early Cambrian: Implications for hyper-enrichment of organic matter 寒武纪早期长江地台（华南）边缘广泛的沿岸上升流：对有机质超富集的影响

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-10-23 DOI: 10.1016/j.palaeo.2024.112569

Jinku Li , Ping Gao , Xianming Xiao , Gary G. Lash , Shuangjian Li , Wei Liu

Early Cambrian Earth history witnessed significant changes in marine environments and biological evolution contemporaneous with extensive accumulation of organic-rich shale. However, major factors controlling hyper-enrichment of organic matter (OM) of lower Cambrian shale deposits remain controversial. Black shale of the lower Cambrian Niutitang Formation (NTT) of the marginal Yangtze Platform (South China) deposited during the Cambrian middle Age 2 are especially organic-rich, with total organic carbon (TOC) concentrations of as much as 13.0 wt%. Geochemical evidence suggests that cool, dry paleo-climatic conditions that prevailed on the Yangtze Platform during the Cambrian Fortunian-late Age 2, induced vigorous coastal upwelling. Paleo-productivity level assessments indicate that the magnitude of primary productivity contemporaneous with deposition of the NTT shale deposits exceeded that of modern upwelling systems (e.g., Peruvian Margin). The widespread occurrence of phosphate nodules within these deposits and decreased Co-EF × Mn-EF values of associated lower Cambrian black shale successions deposited along the margin of the Yangtze carbonate platform suggest extensive coastal upwelling. Widespread and strong coastal upwelling in tandem with elevated surface water primary productivity and anoxic (even euxinic) bottom water conditions are manifested by deposition of OM hyper-enriched black shale during Cambrian Fortunian to middle Age 2 time. However, weakened seasonal upwelling that appears to have prevailed during the late Cambrian Age 2 was accompanied by accumulation of NTT shale deposits of diminished TOC content. In summary, this study provides robust evidence of extensive coastal upwelling along the marginal Yangtze Platform during early Cambrian time that favored accumulation of OM hyper-enriched shale. These results help to elucidate the distribution of high-quality lower Cambrian natural gas source rocks in South China.

早寒武纪地球历史见证了海洋环境和生物进化的重大变化，与此同时，富含有机质的页岩大量堆积。然而，控制下寒武统页岩沉积有机质（OM）超富集的主要因素仍存在争议。华南边缘长江地台下寒武统牛蹄塘地层（NTT）沉积于寒武纪中2世的黑色页岩尤其富含有机质，总有机碳（TOC）浓度高达13.0 wt%。地球化学证据表明，寒武纪富屯系-晚2世期间长江地台普遍存在凉爽、干燥的古气候条件，诱发了活跃的沿岸上升流。古生产力水平评估表明，与 NTT 页岩沉积同时代的初级生产力水平超过了现代上升流系统（如秘鲁边缘）。这些沉积物中磷酸盐结核的广泛出现，以及沿长江碳酸盐岩平台边缘沉积的相关下寒武统黑色页岩沉积的 Co-EF × Mn-EF 值的降低，都表明了广泛的沿岸上升流。在寒武纪富屯系至第二纪中期，广泛而强烈的沿岸上升流与表层水初级生产力的提高和缺氧（甚至缺氧）的底层水条件共同作用，沉积了高OM富集的黑色页岩。然而，寒武纪第 2 纪晚期似乎普遍存在的季节性上升流减弱，伴随着 TOC 含量降低的 NTT 页岩沉积物的积累。总之，本研究提供了有力的证据，表明在寒武纪早期，沿边缘长江地台的广泛沿岸上升流有利于 OM 超富集页岩的堆积。这些结果有助于阐明华南地区优质下寒武统天然气源岩的分布。

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引用次数: 0

Terrestrial response to the Early Cretaceous Weissert Event: Insights from carbon isotope records of organic matter and leaf wax n-alkanes in an inland East Asian lake 早白垩世魏塞特事件的陆地响应：从一个东亚内陆湖的有机物和叶蜡正构烷烃的碳同位素记录中获得的启示

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-10-22 DOI: 10.1016/j.palaeo.2024.112570

Xiaoning Tong , Jianfang Hu , Yanhong Pan , Zuohuan Qin , Dangpeng Xi , Ping’an Peng , Thomas J. Algeo

The Weissert Event (WE), a significant Early Cretaceous environmental disruption, is recognized globally in marine carbonate records for its positive carbon isotope excursion (CIE), organic matter (OM) enrichment, and widespread anoxia. However, records of its terrestrial impact are sparse. This study examines carbon isotope compositions (δ¹³C) from the lacustrine facies of North China's Dabeigou Formation (Yushuxia section, Luanping Basin). The synchronous positive CIEs of total organic carbon (TOC) and C₂₇–C₃₁ n-alkanes within Members 2 to 3 of the Dabeigou Formation corroborate the Weissert Event, marking its first terrestrial observation in North China. Ratios of the isoprenoids pristane and phytane (Pr/Ph), C_org/P ratios and enrichment factors (EFs) of redox-sensitive trace metals (Mo and U) indicate transient anoxic conditions within a mainly oxic-suboxic setting from the late Valanginian to early Hauterivian, which were unfavorable for OM preservation. This highlights that although a global positive CIE occurred during the Weissert Event, anoxia and/or high TOC deposition in inland lakes were not inherent features.

魏塞特事件（Weissert Event，WE）是早白垩世的一次重大环境破坏事件，其碳同位素正偏移（CIE）、有机质（OM）富集和大面积缺氧现象在全球海洋碳酸盐记录中得到公认。然而，有关其对陆地影响的记录却很少。本研究考察了华北大北沟组（滦平盆地榆树峡段）湖沼面层的碳同位素组成（δ13C）。大北沟组2-3层内总有机碳（TOC）和C27-C31正构烷烃的同步正CIE值证实了魏塞特事件，这也是华北地区首次在陆地上观测到魏塞特事件。异戊烷pristane和phytane的比率（Pr/Ph）、Corg/P比率以及对氧化还原反应敏感的痕量金属（Mo和U）的富集因子（EFs）表明，从瓦朗基元晚期到豪特里维元早期，在以缺氧-亚缺氧为主的环境中存在瞬时缺氧条件，不利于OM的保存。这突出表明，虽然魏塞特事件期间出现了全球性的正CIE，但缺氧和/或内陆湖的高TOC沉积并不是其固有特征。

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引用次数: 0

Salinity impacts on n-alkanes in lake sediments of the Badain Jaran Desert, Northwestern China: Implications for paleoclimate reconstruction 盐度对中国西北部巴丹吉林沙漠湖泊沉积物中正烷烃的影响：对古气候重建的影响

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-10-22 DOI: 10.1016/j.palaeo.2024.112571

Meng Li , Zhuolun Li , Shipei Dong , Lin Chen , Xianbao Su , Chen'ao Lu , Aifeng Zhou , Nai'ang Wang

n-Alkanes in lake sediments are essential biomarkers for paleoclimate research, yet the influence of lake salinity on their distribution remains unclear. This study investigates this relationship by analyzing sediments from eight lakes in the Badain Jaran Desert, all subject to similar climatic conditions but varying in salinity. Soil samples from the shoreline vegetation belt and suspended particle matter (SPM) were collected to identify the origin of plant input in the lake sediments. Additionally, sediment samples from the littoral zone to the lake center were all gathered to evaluate the salinity effects at different water depths. Key indexes such as content, the proportion of aquatic macrophyte (P_aq), average chain length (ACL), and carbon preference index (CPI) of n-alkanes were examined to elucidate salinity effects. The result showed that the surrounding vegetation belt is the primary source of n-alkanes in lake sediments, with minimal contributions from SPM. Increased salinity was found to decrease CPI in the littoral zone, while also reducing P_aq and increasing ACL in the lake bottom sediments. Changes of P_aq, ACL and CPI in sediments are not attribute to variations in vegetation belt input but rather suggest that high salinity enhances n-alkane degradation, particularly favoring the degradation of mid-chain compounds in lake bottom sediments. Consequently, the reliability of n-alkane indexes as indicators of aquatic macrophyte in deep lake cores may be compromised by salinity. This study underscores the importance of accounting for salinity effects when using n-alkanes in reconstructing paleoclimate and suggests that their potential as indicators of lake salinization merits further attention.

湖泊沉积物中的正烷烃是古气候研究的重要生物标志物，但湖泊盐度对其分布的影响仍不清楚。本研究通过分析巴丹吉林沙漠八个湖泊的沉积物来研究这种关系，这些湖泊的气候条件相似，但盐度不同。研究人员收集了湖岸植被带的土壤样本和悬浮颗粒物质 (SPM)，以确定湖泊沉积物中植物输入的来源。此外，还收集了从沿岸带到湖心的所有沉积物样本，以评估不同水深的盐度影响。研究了正构烷烃的含量、水生大型植物比例（Paq）、平均链长（ACL）和碳偏好指数（CPI）等关键指标，以阐明盐度效应。结果表明，周围植被带是湖泊沉积物中正烷烃的主要来源，而 SPM 的贡献极小。盐度升高会降低沿岸带的 CPI，同时也会降低 Paq，增加湖底沉积物中的 ACL。沉积物中 Paq、ACL 和 CPI 的变化与植被带输入量的变化无关，而是表明高盐度增强了正烷烃的降解，尤其有利于湖底沉积物中中链化合物的降解。因此，正烷烃指数作为深湖岩心中水生大型植物指标的可靠性可能会受到盐度的影响。这项研究强调了利用正构烷烃重建古气候时考虑盐度影响的重要性，并表明正构烷烃作为湖泊盐化指标的潜力值得进一步关注。

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引用次数: 0

Reliability of the Strontium Isotope Stratigraphy approach in marginal seas: Insights from the Miocene Paratethys 边缘海锶同位素地层学方法的可靠性：中新世帕拉特提斯海的启示

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-10-22 DOI: 10.1016/j.palaeo.2024.112566

Katarína Holcová , Filip Scheiner , Lukáš Ackerman , Rastislav Milovský , Natália Hudáčková , Šárka Hladilová , Slavomír Nehyba , Danuta Peryt

The robustness of the Strontium Isotope Stratigraphy (SIS) as a chemostratigraphic tool was tested in the Miocene epicontinental Central Paratethys using new ⁸⁷Sr/⁸⁶Sr results obtained for 129 foraminiferal tests and various marine invertebrate shells that were converted to numerical ages using the global ⁸⁷Sr/⁸⁶Sr curve for the Phanerozoic open oceans. These ages were compared with those expected from either magnetostratigraphic, radiometric or biostratigraphic studies applied to selected sections from different Central Paratethys basins. The results from different basins showed variations in ⁸⁷Sr/⁸⁶Sr values for specific time intervals; therefore, it is not possible to construct a unique ⁸⁷Sr/⁸⁶Sr curve for the Central Paratethys region that can be used for chemostratigraphic purposes. The ⁸⁷Sr/⁸⁶Sr signal in semi-enclosed basins tends to reflect the lithology of the source areas. For example, marine basins surrounded by areas of Mesozoic carbonate rock cover are associated with a reduced ⁸⁷Sr/⁸⁶Sr signal compared to the global ⁸⁷Sr/⁸⁶Sr signal primarily due to the drainage of these Mesozoic carbonate rocks and transfer of their specific Sr signal. By contrast, areas affected by continental runoff from crystalline terrains in combination with limited connection to surrounding marine domains were found to show an elevated ⁸⁷Sr/⁸⁶Sr signal compared to the global one. Additionally, it was demonstrated that infaunal, eutrophic and hypoxic species (foraminiferal genus Uvigerina and molluscs) show a shift towards a relatively higher ⁸⁷Sr/⁸⁶Sr signal. Therefore, our data show that variable ⁸⁷Sr/⁸⁶Sr patterns occur in semi-enclosed domains, primarily reflecting local settings and thus hampering reliable SIS ages. In particular, the best SIS results in the studied Paratethys area occur during periods of maximum marine connectivity, when other (biostratigraphic) methods can be applied, and then become unreliable as connectivity diminishes.

在中新世上大陆中帕拉特提斯地区，利用对 129 个有孔虫测试和各种海洋无脊椎动物贝壳进行的 87Sr/86Sr 新结果，测试了锶同位素地层学（SIS）作为化合地层学工具的稳健性，并利用新生代开阔洋的全球 87Sr/86Sr 曲线将这些结果转换为数字年龄。将这些年龄与磁地层学、辐射测量学或生物地层学研究中的预期年龄进行了比较，这些研究适用于中帕拉特提斯不同盆地的选定剖面。不同盆地的 87Sr/86Sr 值在特定时间间隔内存在差异；因此，无法为中帕拉特提斯地区构建一条独特的 87Sr/86Sr 曲线，用于化合地层学目的。半封闭盆地中的 87Sr/86Sr 信号往往反映了源区的岩性。例如，与全球 87Sr/86Sr 信号相比，被中生代碳酸盐岩覆盖区域所包围的海洋盆地的 87Sr/86Sr 信号会减弱，这主要是由于这些中生代碳酸盐岩的排水及其特定 Sr 信号的转移。与此相反，受结晶地形大陆径流影响的地区，加上与周围海域的联系有限，87Sr/86Sr 信号高于全球 87Sr/86Sr 信号。此外，研究还表明，底栖生物、富营养化和缺氧物种（有孔虫属 Uvigerina 和软体动物）的 87Sr/86Sr 信号相对较高。因此，我们的数据表明，在半封闭海域出现了多变的 87Sr/86Sr 模式，主要反映了当地的环境，从而妨碍了可靠的 SIS 年龄。特别是，在所研究的帕拉特提斯地区，最好的 SIS 结果出现在海洋连通性最强的时期，此时可以采用其他（生物地层学）方法，而随着连通性的减弱，SIS 结果就变得不可靠了。

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引用次数: 0