Palaeogeography, Palaeoclimatology, Palaeoecology最新文献

Skolithos piperock from the Lower Devonian storm beds 下泥盆统风暴床中的 Skolithos piperock

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-11-14 DOI: 10.1016/j.palaeo.2024.112604

Daniel Sedorko , Dirk Knaust , Marcelo Nery Junior , Gabriel Eduardo Barea de Barros , Victor Ribeiro , Felipe Nascimento Sousa , Renato Pirani Ghilardi , Leonardo Borghi

Skolithos piperock is prevalent in Cambrian shallow marine deposits but diminishes throughout the Paleozoic. This study reports an interval with Skolithos piperock from the upper Furnas Formation (Lower Devonian), offering insights into the paleoenvironmental interpretation of nearshore sandstones. The studied section comprises eight sedimentary facies, transitioning from sandstone-dominated intervals indicative of nearshore environments to siltstone and mudstone facies representing lower energy transitional offshore conditions. Trace fossils are grouped into six ichnocoenoses, reflecting varying depositional settings from proximal to distal in the coastal zone. Notable shifts in ichnocoenosis composition, particularly the transition from Skolithos piperock to the Asterosoma ichnocoenosis, mark stratigraphic boundaries and highlight a transgressive trend between the Furnas and Ponta Grossa formations. The identification of Skolithos piperock provides evidence of storm-generated deposits and reworking activities, which can be applied to basin-scale correlations. This occurrence of a Skolithos piperock is interpreted as the result of several erosive processes triggered by storms, generating a time-averaged ichnoassemblage.

Skolithos琵琶岩在寒武纪浅海沉积中很普遍，但在整个古生代中逐渐减少。本研究报告了上福纳斯地层（下泥盆统）中含有 Skolithos piperock 的一个区段，为近岸砂岩的古环境解释提供了启示。所研究的剖面包括八个沉积层面，从表明近岸环境的砂岩为主的区间过渡到代表低能过渡近岸条件的粉砂岩和泥岩层面。痕量化石被归类为 6 个泥盆化石群，反映了沿岸带从近岸到远岸的不同沉积环境。化石群组成的显著变化，特别是从琵琶岩化石群（Skolithos piperock）向星状化石群（Asterosoma ichnocoenosis）的过渡，标志着地层的边界，突出了富尔纳斯地层和蓬塔格罗萨地层之间的递变趋势。Skolithos piperock 的发现为风暴生成的沉积物和再加工活动提供了证据，可用于盆地尺度的相关性研究。Skolithos piperock 的出现被解释为风暴引发的多个侵蚀过程的结果，产生了时间平均的蛭石组合。

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引用次数: 0

Sedimentary provenance and paleogeographic environment of a Mississippian coal-bearing unit in South China: Constraints from detrital zircon U-Pb ages and sedimentologic and geochemical evidence 华南地区一个密西西比时期含煤单元的沉积产地和古地理环境：来自碎屑锆石U-Pb年龄以及沉积学和地球化学证据的制约因素

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-11-13 DOI: 10.1016/j.palaeo.2024.112605

Yuliang Mu, Rongsong Tian, Yong Fu, Li Yang, Jiang Hu

The Mississippian Xiangbai Formation in South China is one of the oldest coal-bearing sedimentary units in China. However, the sedimentary provenance, paleogeography, and coal formation patterns of the coal-bearing strata are not well constrained. We address this key issue by using a combination of detrital zircon U-Pb data, geochemical analyses of mudstone and shale, drilling data, and geologic field observations. With the exception of the early Paleozoic orogenic events (ca. 440–420 Ma) in the eastern part of the study area, the samples from the Xiangbai Formation exhibit similar detrital zircon U-Pb age distribution with major age peaks at ca. 980–960 Ma and several subordinate age peaks at ca. 800–780 and 600–500 Ma. These detrital zircon grains mainly originated from recycled sedimentary units. Field and drilling data reveal that the Xiangbai Formation was formed in a tidal flat environment with water depth gradually increasing from the bottom to the top, indicating an overall trend of transgression. The Mississippian Xiangbai Formation was deposited in an interglacial period. The Lower Xiangbai Formation was deposited in a relatively cold paleoclimate, gradually transitioning upwards to a warm and humid climate, creating favorable conditions for coal formation. The alternation of warming and cooling climates triggered high-frequency eustatic fluctuations, which led to multiple sedimentary cycles and resulted in thin, unstable coal seams within the Xiangbai Formation. Mississippian sedimentary paleogeography, palaeoclimate, and sedimentary provenance together dominate the coal-bearing clastic sediments in southwestern South China.

华南地区的密西西比系香柏地层是中国最古老的含煤沉积单元之一。然而，该含煤地层的沉积成因、古地理和成煤模式并没有得到很好的解释。我们结合使用了碎屑锆石 U-Pb 数据、泥岩和页岩的地球化学分析、钻探数据以及野外地质观测数据，解决了这一关键问题。除了研究区东部的早古生代造山运动事件（约 440-420 Ma）之外，湘白地层的样品表现出相似的非铁质锆石 U-Pb 年龄分布，主要年龄峰值约为 980-960 Ma，并有几个年龄峰值。锆石U-Pb年龄分布相似，主要年龄峰值约为980-960 Ma，几个次要年龄峰值约为800-780 Ma和600-500 Ma。800-780和600-500 Ma。这些锆英石碎屑主要来自循环沉积单元。野外和钻探资料显示，湘白地层形成于潮平带环境中，水深由下而上逐渐增加，显示出整体的横断趋势。密西西比系祥柏地层沉积于间冰期。湘白下统沉积在相对寒冷的古气候中，逐渐向上过渡到温暖湿润的气候，为煤炭的形成创造了有利条件。气候的冷暖交替引发了高频率的阵风波动，从而导致了多次沉积循环，并在湘白地层中形成了薄而不稳定的煤层。密西西比沉积古地理、古气候和沉积成因共同主导了华南西南部的含煤碎屑沉积。

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引用次数: 0

Paleoenvironmental evolution and East Asian monsoon records through three stages of paleochannels since the mid-pleistocene in the Western Bohai Sea, North China 华北渤海西部更新世中期以来古环境演化和三个阶段古河道的东亚季风记录

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-11-12 DOI: 10.1016/j.palaeo.2024.112603

Shuyu Wu , Jun Liu , Hongxian Chu , Yongcai Feng , Meiling Yin , Lixin Pei

Three stages of paleochannels development, dating back to the Mid-Pleistocene, have been identified in the western Bohai Sea (BS) region. However, the factors controlling their sedimentary formation remain unclear. This study analyzed samples from DZQ01 and adjacent boreholes to establish a chronological framework through AMS ¹⁴C and OSL dating, complemented by grain size and geochemical analyses. End-member analysis using the Generalized Weibull method successfully separated three components: EM1, EM2, and EM3. EM3 (<26.28 μm) reflects the influence of the East Asian Summer Monsoon (EASM), while EM2 (26.28–105.1 μm) is indicative of the East Asian Winter Monsoon (EAWM). Geochemical indicators, such as the Rb/Sr ratio, reflect the impact of paleoclimatic changes. This study identified five major glaciation events since the Mid-Pleistocene. The DU6 unit recorded two glacial stages (300–272 cal. ka B.P.), characterized by a weakened EASM and a stronger EAWM. Similarly, the DU4 unit recorded two glacial stages (165–127 cal. ka B.P.), also marked by a subdued EASM and an enhanced EAWM. The DU2 unit reflects a prolonged glacial stages (71–14 cal. ka B.P.), dominated by the EAWM, resulting in cold and dry conditions. Overall, the uplift of the Tibetan Plateau and sea-level fluctuation significantly influenced the formation and evolution of paleochannels, with the sedimentary characteristics closely tied to the intensities of the East Asian Monsoon (EAM).

渤海（BS）西部地区古河道的三个发展阶段可追溯到中更新世。然而，控制其沉积形成的因素仍不清楚。本研究分析了来自 DZQ01 和邻近钻孔的样品，通过 AMS 14C 和 OSL 测定，并辅以粒度和地球化学分析，建立了年代学框架。采用广义威布尔法进行的末端成分分析成功地分离出三个成分：EM1、EM2 和 EM3。EM3（26.28 μm）反映了东亚夏季季风（EASM）的影响，而 EM2（26.28-105.1 μm）则表明了东亚冬季季风（EAWM）的影响。地球化学指标，如 Rb/Sr 比率，反映了古气候变化的影响。这项研究确定了自中新世以来的五次主要冰川事件。DU6单元记录了两个冰川阶段（公元前300-272 ka.P.），其特点是EASM减弱，EAWM增强。同样，DU4 单元记录了两个冰川期（公元前 165-127 卡），其特征也是 EASM 减弱，EAWM 增强。DU2 单元反映了一个漫长的冰川期（公元前 71-14 千年），以 EAWM 为主，造成了寒冷和干燥的条件。总体而言，青藏高原的隆升和海平面的波动极大地影响了古河道的形成和演化，其沉积特征与东亚季风的强度密切相关。

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引用次数: 0

Late Neogene monsoonal climate in the southeastern margin of the Tibetan Plateau revealed by leaf physiognomy evidence 叶相学证据揭示的青藏高原东南缘新元古代晚期季风气候

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-11-09 DOI: 10.1016/j.palaeo.2024.112583

Zhuo-Er Wang , Gui-Hua Chen , Rui Cao , Zhi-Hui Song , Zhao-Shuai Wang , Huai Wang , Su-Ting Ding , Jing-Yu Wu

Four fossil leaf assemblages from the Late Miocene to the early Late Pliocene of the Tengchong-Lianghe region, western Yunnan, China, are subjected to the Climate-Leaf Analysis Multivariate Program (CLAMP) and Leaf Margin Analysis (LMA) and compared with other late Neogene fossil flora from the southeastern margin of the Tibetan Plateau (SEMTP) and the eastern Himalayan foreland basins to reconstruct paleoclimate and capture ancient monsoon signature. The CLAMP-derived mean annual temperature (MAT) for the Late Neogene in Tengchong-Lianghe range from 17.9 ± 2.3 °C to 21.0 ± 2.3 °C, with the Early Pliocene being the warmest period, while the growing season precipitation (GSP) range from 1905 ± 481 mm to 2006 ± 481 mm with minimal change over time. The CLAMP and LMA results indicate a warmer and wetter climate in the late Neogene of the SEMTP and suggest that the paleoclimate in western Yunnan from the Late Miocene to early Late Pliocene was primarily influenced by global climate evolution rather than topographic changes. CLAMP results indicate that the modern pattern of the Asian Monsoon was established at least by the Late Miocene, though precipitation seasonality in the late Neogene of the SEMTP was weaker than today, likely attributed to the intensification of the East Asian Winter Monsoon driven by global cooling.

对中国云南西部腾冲-梁河地区晚中新世至晚上新世早期的4个叶片化石群进行了气候-叶片多变量分析程序（CLAMP）和叶片边缘分析（LMA），并与青藏高原东南缘（SEMTP）和喜马拉雅前陆盆地东部的其他新近纪晚期植物化石群进行了比较，以重建古气候并捕捉古季风特征。CLAMP得出的腾冲-梁河新近纪晚期年平均气温（MAT）范围为17.9±2.3 °C至21.0±2.3 °C，其中上新世早期是最温暖的时期，而生长季降水量（GSP）范围为1905±481毫米至2006±481毫米，随时间的变化极小。CLAMP和LMA结果表明，东南部海盆新近纪晚期气候较暖较湿，表明晚中新世至晚上新世早期的滇西古气候主要受全球气候演变的影响，而非地形变化。CLAMP的结果表明，至少在晚中新世，亚洲季风的现代模式已经形成，尽管东南季风区新近纪晚期的降水季节性比现在弱，这可能是由于全球变冷导致东亚冬季季风的加强。

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引用次数: 0

Reconstruction of hydroclimate variability in southern Laos from 1885 to 2019 based on Pinus latteri tree-ring data 基于 Pinus latteri 树环数据重建 1885 年至 2019 年老挝南部的水文气候变异性

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-11-08 DOI: 10.1016/j.palaeo.2024.112595

Nakhonekham Xaybouangeun , Zaw Zaw , Rao-Qiong Yang , Shankar Panthi , Dao-Xiong Gao , Viengsy Paothor , Ze-Xin Fan

The climate of Southeast Asia is influenced by the Asian monsoon systems, and inter-annual hydroclimate variability exerts a significant impact on forest ecosystems and agricultural productivity in this region. To improve our understanding of long-term drought variability, this study established ring-width chronologies for Pinus latteri trees at three sites in southern Laos. Site chronologies show negative correlations with temperature and positive correlations with precipitation, the self-calibrated Palmer Drought Severity Index (scPDSI), and the Standardized Precipitation-Evapotranspiration Index (SPEI) during the dry and wet months. The regional composite chronology shows the strongest correlation (r = 0.657, p < 0.001) with SPEI during March–August, indicating that the radial growth of P. latteri in southern Laos is primarily influenced by moisture conditions during the dry-to-wet season. A well-calibrated regression model was employed to reconstruct the variability of March–August SPEI for the period 1885–2019, explaining 43.1 % of the observed SPEI variance during the calibration period 1960–2019. The reconstruction records inter-annual to decadal-scale drought variability in southern Laos including eleven extreme dry years and seven extreme wet years. Notably, the frequency of extreme dry and wet events has increased since the 1970s. The reconstruction shows spectral peaks with periodicities of 2.3–3.1 years and displays negative correlations with sea surface temperatures (SSTs) in the tropical Pacific and Indian oceans, indicating that hydroclimatic variations in southern Laos are driven by large-scale ocean-atmospheric circulations.

东南亚的气候受到亚洲季风系统的影响，年际水文气候变异对该地区的森林生态系统和农业生产力产生了重大影响。为了加深我们对长期干旱变异性的了解，本研究在老挝南部的三个地点建立了松树环宽年代学。在干旱和潮湿月份，地点年轮与温度呈负相关，与降水量、自校准帕尔默干旱严重程度指数（scPDSI）和标准化降水-蒸散指数（SPEI）呈正相关。区域复合年代学与 SPEI 在 3 月至 8 月期间的相关性最强（r = 0.657，p < 0.001），表明老挝南部 P. latteri 的径向生长主要受旱季至雨季期间水分条件的影响。采用校准良好的回归模型重建了 1885-2019 年期间 3-8 月 SPEI 的变异性，解释了 1960-2019 年校准期间 43.1%的观测 SPEI 变异。重建结果记录了老挝南部从年际到十年尺度的干旱变化，包括 11 个极端干旱年和 7 个极端潮湿年。值得注意的是，自 20 世纪 70 年代以来，极端干旱和潮湿事件的频率有所增加。重建显示了周期为 2.3-3.1 年的频谱峰值，并与热带太平洋和印度洋的海表温度（SST）呈负相关，表明老挝南部的水文气候变异是由大尺度海洋-大气环流驱动的。

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引用次数: 0

Ammonites as paleothermometers: Isotopically reconstructed temperatures of the Western Interior Seaway track global records 作为古温度计的鲑鱼：同位素重建的西内海航道温度追踪全球记录

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-11-06 DOI: 10.1016/j.palaeo.2024.112594

Jessie R.C. McCraw , Thomas S. Tobin , J. Kirk Cochran , Neil H. Landman

Ammonites are externally shelled cephalopods that were common in the North American Western Interior Seaway (WIS), and as they grew their aragonitic shells via accretion, they recorded aspects of their environment in the stable isotopic composition of their shells. While the mobility of ammonites may complicate efforts to reconstruct temperatures from their shells, they remain a potentially valuable target for paleothermometry. In this study, we reconstruct the spatial and temporal variability of WIS temperatures using a suite of ammonites (n = 113) spanning the last 25 million years of the Cretaceous along a North-South gradient ranging from the Canadian WIS to the Mississippi Embayment. We present a temporally high-resolution (∼0.6 Ma) oxygen isotope record from these ammonites that indicates cooling temperatures in the WIS of comparable magnitude (∼18 °C +/‐− 4°) to the temperature change seen in global studies, most notably cooling from the Cretaceous Thermal Maximum in the Turonian until the late Maastrichtian. Studies disagree regarding the development and strength of a latitudinal (pole-to-equator) temperature gradient during the Cretaceous; we do not see strong evidence for a latitudinal temperature gradient in the WIS. We do not observe any bias driven by ammonite morphology in our isotopic data, though we suggest that researchers consider the effects of taxonomy and ecological bias on their temperature records. As our ammonite δ¹⁸O record matches the direction and magnitude of global temperature reconstructions, our data imply that ammonites are viable targets for paleothermometry.

芒虫是北美西部内海航道（WIS）中常见的头足类外壳动物，当它们通过增殖长出文石质外壳时，其外壳的稳定同位素组成记录了它们所处环境的方方面面。虽然芒虫的流动性可能会使从其外壳重建温度的工作变得复杂，但它们仍然是古温度测定的潜在目标。在这项研究中，我们利用一套从加拿大WIS到密西西比河海湾的南北梯度上跨越白垩纪最后2500万年的棘皮动物（n = 113），重建了WIS温度的时空变异性。我们展示了这些氨虫的高时间分辨率（∼0.6 Ma）氧同位素记录，结果表明加拿大西印度洋地区的降温幅度（∼18 ° C +/-- 4°）与全球研究中看到的温度变化相当，其中最显著的是图伦纪白垩纪热极盛期至马斯特里赫特晚期的降温。关于白垩纪纬度（极点到赤道）温度梯度的发展和强度，研究结果存在分歧；我们没有发现 WIS 中存在纬度温度梯度的有力证据。虽然我们建议研究人员考虑分类和生态偏差对温度记录的影响，但我们在同位素数据中没有观察到任何由鹦鹉螺形态造成的偏差。由于我们的氨虫δ18O记录与全球温度重建的方向和幅度相吻合，我们的数据意味着氨虫是古温度测定的可行目标。

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引用次数: 0

Functional diversity and resilience of bivalves after the Permian-Triassic mass extinction 二叠纪-三叠纪大灭绝后双壳类动物的功能多样性和恢复力

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-11-04 DOI: 10.1016/j.palaeo.2024.112581

Yanda Wang , Yunfei Huang , Haijun Song , Li Tian , Daoliang Chu , Jinnan Tong

The Permian-Triassic mass extinction was the largest extinction event in the Phanerozoic eon, with profound taxonomic and ecological effects on the ecosystem function. Functional diversity, a facet of biodiversity, could reflect the ecosystem function and stability. Although previous studies have shown that the functional richness of global marine organisms was decoupled from their taxonomic diversity during the mass extinctions, the evolution of functional diversity during the Permian-Triassic mass extinction and its aftermath is still under debate. The ecologically diverse clade bivalves may be more representative for understanding the evolution of functional diversity. To investigate the evolutionary dynamics of the functional diversity of bivalves, a global bivalve dataset of 8929 occurrences from the latest Permian to the Late Triassic was constructed. Functional richness, functional evenness, and functional redundancy were calculated to reflect the functional diversity in this study. Our results showed that the functional richness of bivalves was slightly affected by the Permian-Triassic mass extinction, decoupled from the significant decrease in taxonomic diversity. Meanwhile, a decrease in functional redundancy and an increase in functional evenness were observed after the mass extinction. In addition, bivalves showed high resilience to the mass extinction by maintaining the ecospace and reducing the functional redundancy. The high taxonomic diversity, high functional richness, high functional redundancy and relatively higher proportion of infaunal bivalves during the Late Triassic indicate that the Mesozoic marine revolution was already underway.

二叠纪-三叠纪生物大灭绝是新生代最大的生物灭绝事件，对生物分类学和生态系统功能产生了深远的影响。功能多样性作为生物多样性的一个方面，可以反映生态系统的功能和稳定性。尽管以往的研究表明，在生物大灭绝期间，全球海洋生物的功能丰富性与其分类学多样性脱钩，但二叠纪-三叠纪生物大灭绝期间及其后的功能多样性演化仍存在争议。在了解功能多样性的演化过程中，具有生态多样性的双壳类可能更具代表性。为了研究双壳类功能多样性的演化动态，我们构建了一个从二叠纪晚期到三叠纪晚期的全球双壳类数据集。本研究计算了功能丰富度、功能均匀度和功能冗余度，以反映功能多样性。结果表明，双壳类的功能丰富度受二叠纪-三叠纪大灭绝的影响较小，与分类多样性的显著下降无关。同时，大灭绝后功能冗余度下降，功能均匀度上升。此外，双壳类动物通过维持生态空间和减少功能冗余，在大灭绝中表现出较高的恢复能力。晚三叠世高分类多样性、高功能丰富度、高功能冗余度和相对较高的底栖双壳类比例表明，中生代海洋革命已经开始。

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引用次数: 0

The role of climate on the emergence of giant caimanines (Crocodylia, Alligatoroidea) from the Miocene western Amazonian region 气候对中新世亚马逊河流域西部出现巨型凯门鳄（鳄形目，鳄科）的影响

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-11-03 DOI: 10.1016/j.palaeo.2024.112582

Ana Laura S. Paiva , Pedro L. Godoy , Emma M. Dunne , Alexander Farnsworth , Paul J. Valdes , Daniel J. Lunt , Wilfried Klein , Max C. Langer , Annie S. Hsiou

Extant caimanines include the six modern species of caimans, which occur predominantly in South and Central America and are mostly medium-sized crocodylians. Nevertheless, the fossil record of the group reveals a significantly higher diversity, with remarkable body size variation. In particular, the giants Purussaurus and Mourasuchus, from the Miocene western Amazonian region, are two of the most prominent representatives. Previous work has demonstrated a correlation between the body size of crocodylians and abiotic factors throughout the Cenozoic; however, this relationship is poorly understood, particularly within the Caimaninae lineage. Here, we explore evolutionary body size patterns within Caimaninae, investigating the potential influence of climatic factors. Using a phylogenetically-informed method, we estimated the body size of 33 caimanine specimens, coupled with climatic variables from a General Circulation Model to reconstruct deep-time patterns. Our results indicate that giant Miocene caimanines are restricted to warmer conditions, with significantly less seasonal temperature variation. This suggests that the unmatching climatic conditions of the Miocene western Amazonian region possibly allowed the emergence of unique palaeoecosystems, favouring the sustenance of these very large crocodylians.

现存的凯门鳄包括六个现代凯门鳄物种，主要分布在南美洲和中美洲，多为中型鳄科动物。然而，化石记录显示，该类动物的多样性要高得多，体型差异显著。特别是中新世亚马逊河西部地区的巨鳄 Purussaurus 和 Mourasuchus 是其中两个最突出的代表。以往的研究表明，在整个新生代，鳄科动物的体型与非生物因素之间存在着相关性；然而，人们对这种关系还知之甚少，尤其是在凯门鳄科（Caimaninae）中。在这里，我们探讨了巨蜥科的体型进化模式，研究了气候因素的潜在影响。利用系统发育信息方法，我们估算了 33 个凯门鳄标本的体型，并结合大气环流模型中的气候变量重建了深时模式。我们的研究结果表明，巨型中新世凯门鳄局限于较温暖的环境，季节性温度变化明显较小。这表明，中新世亚马逊河西部地区不匹配的气候条件可能允许出现独特的古生态系统，有利于这些大型鳄科动物的生存。

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引用次数: 0

Improved chronostratigraphy and fine-tuned timing for Late Triassic palaeoenvironmental changes in SW Britain using coupled magnetic polarity and carbon isotope stratigraphy 利用磁极和碳同位素耦合地层学改进英国西南部晚三叠世古环境变化的年代地层学和微调时间

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-11-03 DOI: 10.1016/j.palaeo.2024.112579

Mark W. Hounslow , Julian E. Andrews

Understanding the synchronicity of global climatic, environmental, and biotic events around the Norian-Rhaetian boundary (NRB) is problematic because of major international differences in biochronology. We instead use magnetostratigraphic and global carbon isotopic changes to produce more precise global correlation. This work focusses on the base and top of the Rhaetian, with principal age control from a new late Norian to latest Rhaetian magnetostratigraphy from Lavernock (southern Wales) which can be directly correlated to the proposed NRB sections at Pignola Abriola (Italy) and Steinbergkogel (Austria). A disconformity exists in the Lavernock section in its late Norian part (Branscombe Mudstone Formation), but the NRB interval is largely complete. The magnetostratigraphy and a composite δ¹³C_org stratigraphy from three British sections, demonstrate synchronous changes in both terrestrial and marine records. This analysis indicates the older proposed definition of the NRB from Steinbergkogel is in the upper few metres of the Branscombe Mudstone Formation, while the younger NRB definition from Pignola Abriola is in the upper parts of the Blue Anchor Formation. The latest Rhaetian magnetostratigraphy from Lavernock records reverse magnetochrons UT26r and UT28r which closely pre-date and post-date the widely recognised Marshi and Spelae carbon isotope excursions, respectively. Magnetochrons UT28r and UT27r were previously recognised at St Audrie's Bay (SW England), with relationships to the Newark Supergroup which tightly constrain the first phase of CAMP eruptions to overlap the Spelae excursion. The carbon isotope excursions present in the Blue Anchor Formation lacustrine successions, demonstrate the likely atmospheric, and global spread of these perturbations.

由于生物年代学方面的巨大国际差异，要理解纪-雷新世边界（NRB）附近全球气候、环境和生物事件的同步性是一个难题。我们转而使用磁地层学和全球碳同位素变化来产生更精确的全球相关性。这项工作的重点是雷蒂纪的底部和顶部，主要的年龄控制来自拉弗诺克（威尔士南部）新的晚纪至最新雷蒂纪磁地层，该地层可与皮尼奥拉-阿布里奥拉（意大利）和斯坦伯格科格尔（奥地利）的拟议 NRB 断面直接相关。拉弗诺克断面在其晚纪部分（布兰斯科姆泥岩地层）存在一个断裂，但北回归线区间基本完整。英国三个断面的磁地层学和综合 δ13Corg 地层学显示了陆地和海洋记录的同步变化。分析表明，Steinbergkogel 提出的较早的 NRB 定义位于 Branscombe 泥岩层的上部几米处，而 Pignola Abriola 提出的较早的 NRB 定义位于蓝锚层的上部。拉弗诺克（Lavernock）最新的雷蒂期磁地层记录了反向磁ochron UT26r 和 UT28r，它们分别紧跟在广为人知的马西（Marshi）和斯佩莱（Spelae）碳同位素偏移之前和之后。磁ochrons UT28r 和 UT27r 以前在 St Audrie's Bay（英格兰西南部）得到过确认，它们与 Newark 超群的关系严格限制了 CAMP 喷发的第一阶段与 Spelae 偏移的重叠。蓝锚地层湖沼演替中出现的碳同位素偏移表明，这些扰动可能在大气中和全球范围内扩散。

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引用次数: 0

Meteorological influences on marine chemistry during the Cryogenian Sturtian glaciation 低碳史图尔特冰川时期气象对海洋化学的影响

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-11-03 DOI: 10.1016/j.palaeo.2024.112573

Shengxian Zhu , Xianguo Lang , Kun Zhao , Chaochao Xing , Mingcai Hou

The Cryogenian Sturtian glaciation (717–660 Ma) represents the most extreme icehouse climate condition in Earth's history, during which the global ocean was completely frozen, known as the Snowball Earth event. It is widely accepted that such a global freeze could result in persistent anoxic and ferruginous marine conditions. Here, we report on a Sturtian-aged storm-prone shelf (ca. 678 Ma) in South China, characterized by dynamic fluctuations in marine redox conditions. We observe a sequence of transitions from euxinic (anoxic and H₂S-enriched) to ferruginous (anoxic but iron-rich), and finally to oxic conditions on this shelf. The euxinic deposits frequently exhibit hummocky/swaley cross-bedding structures (HCS/SCS) and contain high levels of authigenic francolite. In contrast, the ferruginous interval displays rare occurrences of HCS/SCS and lower amounts of authigenic francolite. Conversely, the oxic deposits show no evidence of storm activity. These results suggest that the strong storm waves played a crucial role in facilitating the upwelling of phosphorus-enriched deep water, thereby creating favorable nutrient conditions that stimulated primary productivity and microbial sulfate reduction (MSR). These findings underscore the significant influence of local meteorological conditions, particularly storm activity, on marine redox changes. Furthermore, dynamic storm-induced currents combined with marine redox conditions indicate the presence of an unfrozen sea with active biogeochemical cycles during the Cryogenian Sturtian glaciation. This study confirms the complex interactions among meteorology, oceanography, and Earth's climate system during extreme glacial events.

冰河时期（717-660 Ma）代表了地球历史上最极端的冰室气候条件，在此期间全球海洋完全冻结，被称为 "雪球地球 "事件。人们普遍认为，这样的全球冰冻会导致持续的缺氧和铁锈海洋条件。在此，我们报告了华南一个斯都尔纪风暴易发大陆架（约 678 Ma）的情况，其特征是海洋氧化还原条件的动态波动。我们观察到该大陆架从缺氧（缺氧和富含 H2S）到铁锈色（缺氧但富含铁），最后到缺氧条件的一系列转变。缺氧沉积物经常呈现驼峰状/漩涡状交叉层理结构（HCS/SCS），并含有大量自生钫石。与此相反，铁砾岩层间很少出现驼峰状/漩涡状交叉层结构，自生钫石的含量也较低。相反，含氧沉积物则没有风暴活动的迹象。这些结果表明，强烈的风暴潮在促进富磷深水上涌方面发挥了关键作用，从而创造了有利的营养条件，刺激了初级生产力和微生物硫酸盐还原（MSR）。这些发现强调了当地气象条件，特别是风暴活动对海洋氧化还原变化的重要影响。此外，由风暴引起的动态海流与海洋氧化还原条件相结合，表明在低冰期的斯图尔特冰川中存在着一个生物地球化学循环活跃的不冻海。这项研究证实了极端冰川事件期间气象学、海洋学和地球气候系统之间复杂的相互作用。

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引用次数: 0