Palaeogeography, Palaeoclimatology, Palaeoecology最新文献_第8页

A new regime of herbivory from diverse plant–arthropod interactions from the Middle Jurassic of northeastern China 从中国东北中侏罗世植物与节肢动物的不同互动中发现新的草食动物体系

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-09-23 DOI: 10.1016/j.palaeo.2024.112511

Lifang Xiao , Yuekun Wu , Liang Chen , Conrad C. Labandeira , Chungkun Shih , Qiaoling Ding , Dong Ren , Yongjie Wang

Qualitative and quantitative evaluation of insect herbivory is important for understanding the complex and diverse plant–insect associations in terrestrial ecosystems during the mid Mesozoic. We examined 2503 plant specimens from the Mid-Jurassic (Callovian, 165 Ma) Jiulongshan Formation, a gymnosperm-dominant, fern subdominant plant assemblage at Daohugou, northeastern China, where 149 species/morphotypes from 11 plant groups were identified. Based on the functional feeding group–damage type (FFG-DT) system, we detected a richness of 11 FFGs and 78 DTs, frequency of 2329 DTs, 8045 feeding event occurrences, and herbivory index of 3.27 %. Major consumption occurred on broad-leaved of bennettitaleans, accounting for half of all herbivory indicated by multiple indices, and ginkgoaleans, less so for narrow-leaved of conifers. The top-four feeding groups were margin feeding, piercing and sucking, oviposition, and galling; all groups displayed a pattern of narrow DT functional-breadth (22.22 %) and twofold increase of broad DT functional-breadth (48.15 %). Physical plant defenses were found on the most herbivorized plant host implying trade-offs between host physiology and insect herbivory. Compared with other gymnosperm-dominated assemblages, the elevated richness and intensity of Daohugou herbivory indicates a new regime of resource consumption that occurred by late Middle Jurassic time associated with predator and especially parasitoid diversification.

昆虫草食性的定性和定量评估对于了解中生代中期陆地生态系统中复杂多样的植物-昆虫关系非常重要。我们研究了中国东北道虎沟中侏罗世（卡勒维世，165 Ma）九龙山地层的2503株植物标本，该地层是一个以裸子植物为主、蕨类植物为辅的植物群落，共鉴定出11个植物类群的149种/型。根据功能取食群-损害类型（FFG-DT）系统，我们发现了11个功能取食群和78个损害类型，2329个损害类型，8045次取食事件，草食指数为3.27%。主要的取食发生在阔叶树和银杏树上，占多种指数显示的取食总量的一半，针叶树的窄叶取食量较少。前四类取食方式分别是边缘取食、穿刺和吮吸、产卵和瘿咬；所有取食方式都显示出窄DT功能宽度（22.22%）和宽DT功能宽度增加两倍（48.15%）的模式。植物物理防卫作用出现在食草量最大的植物寄主上，这意味着寄主生理机能与昆虫食草量之间存在权衡。与其他以裸子植物为主的生物群落相比，道虎沟草食性生物的丰富程度和强度都有所提高，这表明在中侏罗世晚期出现了一种新的资源消耗机制，与捕食者尤其是寄生虫的多样化有关。

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引用次数: 0

Synchrotron-based P K-edge XANES spectroscopy reveals the transition of phosphorus cycling in the early Cambrian ocean 基于同步加速器的 P K 边 XANES 光谱揭示了寒武纪早期海洋磷循环的转变

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-09-21 DOI: 10.1016/j.palaeo.2024.112506

Pengcheng Ju , Zhenfei Wang , Chao Chang , Zhangqin Zheng , Run Li , Wenpeng Xia , Xuyang Cao , Yigui Han , Mingyu Zhao , Chao Li , Xingliang Zhang , Kang-Jun Huang

Phosphorus, as a long-term limiting nutrient, is essential for the rapid animal diversification in the early Cambrian ocean. However, the widespread occurrence of phosphorites during this period indicates anomalous phosphorus cycling mechanisms that remain inadequately explored. To investigate the interplay between marine redox conditions and phosphorus cycling, we used geochemical proxies and synchrotron-based P K-edge X-ray Absorption Near Edge Structure (XANES) spectroscopy to analyze the Cambrian Terreneuvian Yurtus Formation (Fortunian to Stage 2) from the Tarim Block. Redox-sensitive elements, iron speciation and nitrogen isotopes reveal an expansion of the surface oxygenated waters, despite persistent ferruginous bottom waters. Moreover, a shift of phosphorus speciation was observed in bedded cherts via P K-edge XANES, suggesting a transition of phosphorus cycling. Specifically, the samples exhibit low total phosphorus contents with a high rate of carbonate-fluorapatite authigenesis in the lower Yurtus Formation. This is followed by an increase in the proportion of terrestrial-derived fluorapatite and iron-bound phosphorus, corresponding to the expansion of surface oxygenated waters. Our findings reveal a significant shift in dominant phosphorus speciation in the early Cambrian marine sediments, which is intricately linked to the coupled phosphorus‑iron‑carbon‑oxygen cycles in the Cambrian ocean.

磷作为一种长期的限制性营养元素，对寒武纪早期海洋动物的快速多样化至关重要。然而，这一时期磷酸盐岩的广泛出现表明磷循环机制异常，而对这一机制的探索仍然不足。为了研究海洋氧化还原条件与磷循环之间的相互作用，我们利用地球化学代用指标和基于同步辐射的 P K 边 X 射线吸收近缘结构（XANES）光谱分析了塔里木地块的寒武纪特提尼安玉尔都斯地层（福尔图安至第二阶段）。氧化还原敏感性元素、铁元素种类和氮同位素显示，尽管底层水持续含铁，但表层含氧水域却在扩大。此外，通过 P K-edge XANES，还观察到层积岩中磷的种类发生了变化，这表明磷循环发生了转变。具体地说，在尤尔图斯地层下部，样品显示总磷含量较低，碳酸盐-氟磷灰石自生速率较高。随后，源于陆地的氟磷灰石和铁结合磷的比例增加，这与地表含氧水域的扩大相对应。我们的发现揭示了早寒武纪海洋沉积物中主要磷物种的重大变化，这与寒武纪海洋中磷-铁-碳-氧的耦合循环密切相关。

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引用次数: 0

Sensitive response of erosion and weathering to the Indian Summer Monsoon changes in South Asia during Dansgaard-Oeschger oscillations 丹斯加德-奥什格振荡期间南亚地区的侵蚀和风化对印度夏季季风变化的敏感反应

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-09-21 DOI: 10.1016/j.palaeo.2024.112516

Jingrui Li , Xuefa Shi , Shengfa Liu , Fangliang Li , Xiaoming Miao , Rui Jiang , Somkiat Khokiattiwong , Narumol Kornkanitnan

Continental weathering plays a key role in regulating the long-term climate stability via negative feedback. However, whether and how erosion and weathering respond to rapid climate change (e.g millennial scale) in large river basins remains unclear, partly due to the lack of archives with robust age models and high sampling resolution. As one of the largest sediment source-to-sink systems, the Himalaya-Ganga/Brahmaputra River-Bay of Bengal system is considered as an ideal laboratory for examining the weathering-climate relationships over the past. Here we present the elemental and mineralogical data from well age-constrained core sediments in the Bay of Bengal, which document the erosion and weathering conditions in South Asia during the last glacial period. All proxies generally show larger values during glacial interstadials than the stadials, consistent with the millennial variabilities of regional sea surface temperature (SST) and the Indian Summer Monsoon (ISM) strength. We confirm that the erosion and chemical weathering signals in Ganga/Brahmaputra River basins, which sensitively respond to the ISM strength and/or temperature change, could be propagated through the large river systems and faithfully preserved in the South Asian marginal seas, without noticeable time lag on a millennial scale. Our findings provide valuable data for response of erosion and weathering dynamics in a large river basin to rapid climate changes, and highlight the immense potential of monsoon-driven continental silicate weathering in floodplains as a substantial short-term carbon sink, thus underscoring a pivotal natural carbon sequestration mechanism amidst the escalating threat of global warming.

大陆风化在通过负反馈调节长期气候稳定性方面发挥着关键作用。然而，大河流域的侵蚀和风化是否以及如何应对快速气候变化（如千年尺度）仍不清楚，部分原因是缺乏具有可靠年龄模型和高采样分辨率的档案。作为最大的沉积物源-汇系统之一，喜马拉雅-甘加/布拉马普特拉河-孟加拉湾系统被认为是研究过去风化-气候关系的理想实验室。在此，我们介绍了来自孟加拉湾年龄约束良好的岩心沉积物的元素和矿物学数据，这些数据记录了上一个冰川期南亚的侵蚀和风化条件。所有代用指标在冰川期间期的数值普遍大于冰川期末期的数值，这与区域海面温度（SST）和印度夏季季风（ISM）强度的千年变异是一致的。我们证实，恒河/布拉马普特拉河流域的侵蚀和化学风化信号对印度夏季季候风强度和/或温度变化敏感，可通过大河系统传播并忠实地保存在南亚边缘海中，不会出现明显的千年尺度时滞。我们的发现为大河流域的侵蚀和风化动力学对快速气候变化的响应提供了宝贵的数据，并凸显了季风驱动的洪泛平原大陆硅酸盐风化作为大量短期碳汇的巨大潜力，从而强调了在全球变暖的威胁不断升级的情况下一个关键的自然碳固存机制。

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引用次数: 0

Outburst floods and their impact on Chinese Neolithic cultures during the 4.2 ka BP event: Evidence from Dayeze Lake in the lower reaches of the Yellow River 公元前4.2ka时期的溃决性洪水及其对中国新石器时代文化的影响：来自黄河下游大冶泽湖的证据

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-09-21 DOI: 10.1016/j.palaeo.2024.112513

Jinjia Wu , Yuan Li , Yingying Liu , Xingxing Liu , Zhanfang Hou , Rui Zhang , Shiyue Chen

Abrupt climate fluctuations between 4.2 and 3.5 ka BP, and in particular the 4.2 ka BP event, exerted a profound impact on the global ancient civilizations. However, hydroclimatic conditions within the Asian Summer Monsoon (ASM) regions during this event remain uncertain. Here we report a multi-proxy analysis of a sediment core obtained from Dayeze Lake in the lower reaches of the Yellow River in monsoonal China, to elucidate the hydroclimatic variabilities over the past 4.2 ka. Core intervals (4.2–3.5, 1.1–0.6 cal ka BP) containing high levels of sand fraction, low-frequency magnetic susceptibility and zirconium, and low levels of organic matter and calcium oxide, reflect outburst floods from the Yellow River. This is supported by the widespread fluvial deposits and slackwater deposits preserved in archaeological sites and loess-paleosol profiles from the middle and lower reaches of the Yellow River. In contrast, various climate records, such as lake level, pollen, and tree ring data, from the marginal regions of the ASM reflect widespread droughts during the same time period. This finding highlights the significant spatial heterogeneity of hydroclimate within ASM regions associated with the 4.2 ka BP event, which may be related to migrations of the monsoonal rain belt and the West Pacific subtropical high, as well as frequent El Niño–Southern Oscillation events. Referring to archaeological data, we conclude that the decline and collapse of Chinese Neolithic cultures were related to a pattern of droughts in the marginal regions of the ASM and floods in the middle and lower reaches of the Yellow River.

公元前 4.2 至 3.5 kaP 之间的气候剧烈波动，尤其是公元前 4.2 kaP 事件，对全球古代文明产生了深远影响。然而，这一事件期间亚洲夏季季风（ASM）地区的水文气候条件仍不确定。在此，我们报告了对中国季风区黄河下游大冶泽湖沉积物岩芯的多代理分析，以阐明过去 4.2 ka 期间的水文气候变异。含有高含量砂分、低频磁感应强度和锆以及低含量有机质和氧化钙的岩芯区段（4.2-3.5，1.1-0.6 cal ka BP）反映了黄河溃决洪水。考古遗址和黄河中下游黄土-页岩剖面中保存的广泛的河流沉积和松散水沉积也证明了这一点。相比之下，ASM 边缘地区的各种气候记录（如湖泊水位、花粉和树环数据）则反映了同一时期的普遍干旱。这一发现凸显了与 4.2 ka BP 事件相关的 ASM 区域内水文气候的显著空间异质性，这可能与季风雨带和西太平洋副热带高压的迁移以及频繁的厄尔尼诺-南方涛动事件有关。根据考古资料，我们得出结论：中国新石器时代文化的衰落和崩溃与ASM边缘地区的干旱和黄河中下游的洪水模式有关。

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引用次数: 0

Large river expansion and global cooling controlled the Plio-Pleistocene weathering intensity records in East Asian margin 大河扩张和全球变冷控制了东亚边缘的上新世-更新世风化强度记录

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-09-21 DOI: 10.1016/j.palaeo.2024.112517

Fangliang Li , Shouye Yang , Daniel O. Breecker , Yulong Guo , Evan J. Ramos , Xiangtong Huang , Kai Deng , Jimin Yu , Sanzhong Li

Silicate weathering has long been considered to maintain the Earth's climate stability, yet how the weathering responds to the late Cenozoic cooling remains unclear, partly because of the complicated factors which obscure the weathering records. Large rivers in East Asia integrate continental weathering history, but how the source-to-sink system evolution affected the weathering signals need to be clarified. We compile proxy data of Nd isotopes, zircon ages and Chemical Index of Alteration (CIA) in East Asian margin and source terranes, along with new proxy data from core CSDP-2 in the shelf region, to understand the large river evolution and assess their influence on weathering proxy records. The median εNd values of East Asian marginal sediments increased from −18.8 in pre-3.6 Ma period to −11.3 since the 1.0 Ma, corresponding to the isotopic signatures in North China Craton and Northeastern (NE) Tibetan Plateau/Loess Plateau terranes, respectively. The zircon ages further confirmed the provenance shift, hinting that the modern-like Huanghe (Yellow River) system has been fully integrated during early Pleistocene, no later than ∼1.0 Ma. This integration facilitated the sediment transportation from plateaus into the continental margin. Consequently, the CIA records in marginal regions show a more significant decrease than other Asian regions, within the context of Plio-Pleistocene cooling. Our study found that the upland expansion of large river system and global cooling jointly controlled the decline in the weathering intensity records, highlighting the importance to understand the evolution of source-to-sink system before interpreting the weathering signals from the continental margin sediments.

长期以来，硅酸盐风化作用一直被认为是维持地球气候稳定的重要因素，但风化作用如何对新生代晚期的冷却做出反应仍不清楚，部分原因是复杂的因素掩盖了风化作用的记录。东亚的大江大河整合了大陆的风化历史，但是源-汇系统演化如何影响风化信号仍有待澄清。我们汇编了东亚边缘和源地的钕同位素、锆石年龄和化学蚀变指数（CIA）等代用数据，以及大陆架地区CSDP-2岩芯的新代用数据，以了解大河流演化并评估其对风化代用记录的影响。东亚边缘沉积物的εNd中值从3.6Ma以前的-18.8增加到1.0Ma以来的-11.3，分别与华北克拉通和青藏高原东北部/黄土高原陆相的同位素特征相对应。锆石年龄进一步证实了来源的转变，暗示了类似现代的黄河（黄河）水系在早更新世就已经完全整合，时间不晚于 1.0 Ma。这种整合促进了沉积物从高原进入大陆边缘。因此，在上新世-更新世变冷的背景下，边缘地区的CIA记录比其他亚洲地区的CIA记录显示了更显著的减少。我们的研究发现，大江大河系统的高地扩张和全球变冷共同控制了风化强度记录的下降，突出了在解释来自大陆边缘沉积物的风化信号之前了解源-汇系统演化的重要性。

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引用次数: 0

Multi-proxy reconstruction of climate changes from the Medieval Climate Anomaly to the Little Ice Age in Southeast China 中国东南地区从中世纪气候异常到小冰河时期气候变化的多代理重建

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-09-19 DOI: 10.1016/j.palaeo.2024.112510

Lin Zhao , Chunmei Ma , Xiaojian Zhang , Liang Li , Huayu Lu

Exploring climate fluctuations across geological eras provides crucial historical context for addressing contemporary global climate challenges. This research leverages multi-proxies records analytical techniques, including pollen and charcoal analysis, X-ray fluorescence (XRF), and assessments of humification degree and loss on ignition (LOI), alongside paleoclimate simulations based on an alpine peat bog in Jiangxi Province, Southeast China. The study aims to provide a comprehensive review of vegetation evolution, climatic shifts, East Asian summer monsoon (EASM) intensity, and the potential drivers behind EASM behavior over the past two millennia. Our findings reveal a significant transition in precipitation and temperature patterns from the Medieval Climate Anomaly (MCA, 960–1420 CE) to the Little Ice Age (LIA, 1420–1850 CE). A distinct pattern emerges, highlighting particularly wet periods occurring between 960–1050 CE, 1190–1250 CE, and 1350–1400 CE, as well as significant droughts during 1430–1550 CE, 1590–1650 CE, 1680–1720 CE, and 1750–1800 CE. When compared to our temperature reconstruction series and precipitation data, a clear correlation emerges—wet phases align with warmer period characteristic of the MCA. Based on our simulation results, we suggest that ENSO oscillations and the Indo-Pacific warm pool played a substantial role in driving climate dynamics from the MCA to the LIA.

探索不同地质年代的气候波动为应对当代全球气候挑战提供了重要的历史背景。这项研究利用多种代用指标记录分析技术，包括花粉和木炭分析、X射线荧光（XRF）、腐殖化程度和点火损失（LOI）评估，以及基于中国东南部江西省高山泥炭沼泽的古气候模拟。该研究旨在全面回顾过去两千年来的植被演变、气候转变、东亚夏季季风强度以及东亚夏季季风行为背后的潜在驱动因素。我们的研究结果表明，从中世纪气候异常（MCA，公元960-1420年）到小冰河时期（LIA，公元1420-1850年），降水和温度模式发生了重大转变。一个明显的模式出现了，突出表现在西元960-1050年、西元1190-1250年和西元1350-1400年的特别湿润时期，以及西元1430-1550年、西元1590-1650年、西元1680-1720年和西元1750-1800年的严重干旱时期。与我们的温度重建序列和降水数据相比，我们发现了一个明显的相关性--湿润阶段与 MCA 的温暖时期特征一致。根据我们的模拟结果，我们认为厄尔尼诺/南方涛动振荡和印度洋-太平洋暖池在驱动从 MCA 到 LIA 的气候动态中发挥了重要作用。

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引用次数: 0

Blue carbon storage of tidal flats and salt marshes: A comparative assessment in two Chinese coastal areas 滩涂和盐沼的蓝碳储存：两个中国沿海地区的比较评估

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-09-19 DOI: 10.1016/j.palaeo.2024.112509

Jinge Zhou , Lulu Zhang , Jingfan Zhang , Shuchai Gan , Zhe Lu , Guoming Qin , Xingyun Huang , Han Chen , Hua He , Yongxing Li , Yingwen Li , Hui Li , Faming Wang

Coastal wetlands are blue carbon (C) reservoirs and play an important role in mitigating climate change by efficiently capturing and storing organic carbon (OC). However, assessments of blue C sequestration focus primarily on soil organic carbon (SOC) inventories of vegetated coastal ecosystems and often neglect the potential of tidal flats to sequestrate C. To address the issue, a comparative assessment was carried out for two representative coastal wetlands in China: the Yellow River Delta and Yancheng coastal wetlands. The study focused on distinct types of coastal ecosystems including unvegetated tidal flats and three types of salt marshes vegetated by either Spartina alterniflora, Suaeda salsa, or Phragmites australis. We combined field sampling and data synthesis to assess the OC stock of different coastal areas and evaluate the regional OC storage. The results indicated that vegetated salt marshes exhibited higher OC stocks per unit area compared to unvegetated tidal flats in both regions. Interestingly, tidal flats in the Yellow River Delta displayed comparable OC stocks to S. salsa marsh on the Yancheng coast. The regional OC storage was estimated to be 5.64 ± 0.61 Tg C for the Yellow River Delta and 9.96 ± 1.52 Tg C for the Yancheng coast. Tidal flats with low SOC stock per unit area were the primary contributors to regional OC storage, accounting for over 75 % of the total. This predominance was attributed to the extensive distribution of tidal flats along China's coast, indicating their significant potential as blue C sinks. Overall, this study provides insights into the OC storage potential of various wetland types in China and highlights the importance of considering tidal flats in estimates of blue C sequestration.

沿海湿地是蓝碳库，通过有效捕获和储存有机碳 (OC) 在减缓气候变化方面发挥着重要作用。然而，对蓝碳封存的评估主要集中在沿海植被生态系统的土壤有机碳（SOC）清单上，往往忽视了滩涂封存碳的潜力。研究的重点是不同类型的沿岸生态系统，包括无植被滩涂和由互花叶斯巴达（Spartina alterniflora）、莎草（Suaeda salsa）或葭藻（Phragmites australis）植被覆盖的三种盐沼。我们结合实地取样和数据综合，评估了不同沿海地区的 OC 储量，并评价了区域 OC 储量。结果表明，在这两个地区，与未植被的滩涂相比，植被盐沼的单位面积 OC 储量更高。有趣的是，黄河三角洲滩涂的 OC 储量与盐城沿海的莎莎沼泽相当。据估计，黄河三角洲的区域 OC 储量为 5.64 ± 0.61 Tg C，盐城沿海为 9.96 ± 1.52 Tg C。单位面积 SOC 储量较低的滩涂是区域 OC 储量的主要来源，占总量的 75% 以上。这种优势是由于滩涂在中国沿海的广泛分布，表明其作为蓝色碳汇的巨大潜力。总之，这项研究深入揭示了中国各种湿地类型的 OC 储存潜力，并强调了在估算蓝 C 固存量时考虑滩涂的重要性。

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引用次数: 0

Extreme drought events and land surface temperature variations on the northeastern Tibetan Plateau over the last 350 ka 过去 350 ka 年青藏高原东北部的极端干旱事件和地表温度变化

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-09-19 DOI: 10.1016/j.palaeo.2024.112507

Shaohua Tian , Gaowen Dai , Guoqiao Xiao , Huan Yang , Xiaoqing Meng , Qiuzhen Yin

The northeastern Tibetan Plateau (NETP) is located in the ecologically vulnerable northwestern China, with semi-humid and semi-arid conditions. Long-term paleo-hydrological and paleo-temperature variations and their mechanisms over the NETP remain ambiguous, primarily due to the limited availability of well-dated, long-term depositional archives and suitable proxies. In this paper, we investigate climate variations and their underlying mechanisms in the region using Glycerol Dialkyl Glycerol Tetraethers (GDGTs) spanning the last 350 ka. Our results suggest that the NETP underwent substantial drying during glacial periods, with the driest period occurring during the last glacial period. The intensity of drought during glacial periods is comparable to that in the Westerlies-dominated region but differs from that in the East Asian monsoon region. This suggests that the influence of the Westerlies surpassed that of the East Asian summer monsoon (EASM), becoming the major driver of warm-season drought events on the NETP during glacial periods. Additionally, the peaks of aridity events coincide with summer insolation maxima during glacial periods, which may be related to the direct influence of local insolation on regulating evaporation. The reconstructed land surface temperatures were about 6.7 °C during interglacial periods and 2.6 °C during glacial periods, which may be linked to a combination of variations in insolation, CO₂ levels, and other internal feedback mechanisms. However, an unusual warming occurred during the last glaciation, with an average temperature of about 4.8 °C. This warming may be related to variations in soil moisture and vegetation resulting from extreme drought. Our study highlights the sensitivity of hydrological variations over the NETP to insolation and Westerlies, as well as the critical roles of soil moisture and vegetation in land surface temperature variations.

青藏高原东北部（NETP）位于生态脆弱的中国西北部，属于半湿润和半干旱地区。青藏高原的长期古水文和古气温变化及其机制仍不明确，主要原因是年代久远的长期沉积档案和合适的代用指标有限。在本文中，我们利用跨越过去 350 ka 的甘油二烷基甘油四醚（GDGTs）研究了该地区的气候变化及其内在机制。我们的研究结果表明，在冰川期，NETP 经历了严重的干旱，其中最干旱的时期出现在上一个冰川期。冰川期的干旱强度与西风带主导地区的干旱强度相当，但与东亚季风区的干旱强度不同。这表明西风的影响超过了东亚夏季季风的影响，成为冰川期暖季干旱事件的主要驱动力。此外，干旱事件的峰值与冰川期夏季日照最大值相吻合，这可能与当地日照对调节蒸发的直接影响有关。重建的陆地表面温度在间冰期约为 6.7 ℃，在冰川期约为 2.6 ℃，这可能与日照、二氧化碳水平和其他内部反馈机制的综合变化有关。然而，最后一次冰川期出现了不寻常的变暖，平均气温约为 4.8 ℃。这种变暖可能与极端干旱导致的土壤湿度和植被变化有关。我们的研究凸显了北太平洋水文变化对日照和西风的敏感性，以及土壤水分和植被在地表温度变化中的关键作用。

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引用次数: 0

Environmental changes in the Fleuve Manche paleoriver drainage system (Western Europe) linked to North Atlantic sub-millennial climate variability across Heinrich Stadial 1: Palynological evidence from the Bay of Biscay Fleuve Manche 古河流排水系统（西欧）的环境变化与跨海因里希晚期 1 的北大西洋亚千年气候多变性有关：来自比斯开湾的古植物学证据

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-09-19 DOI: 10.1016/j.palaeo.2024.112512

Aurélie Penaud , Wiem Fersi , Samuel Toucanne , Maria Fernanda Sánchez Goñi , Linda Rossignol , Filipa Naughton , Mélanie Wary , Frédérique Eynaud

Marine microfossils (dinoflagellate cysts and planktonic foraminifera) and geochemical (XRF-Ti/Ca)-based climatic records from a core (MD13–3438) located off the Fleuve Manche (FM) paleo-mouth have revealed that sustained warm summer sea surface temperatures (SSTs) during sub-millennial climate changes within HS1 (∼18–14.7 ka) may have played a key role in the FM regime related to the European Ice Sheet (EIS) melting rate. In this study, we have analyzed the MD13–3438 pollen content over the HS1 at a mean resolution of ∼50 years to test whether vegetation-based air temperatures were coupled to SSTs face to this rapid climate variability. First, our results highlight two major phases of pollen sources at site MD13–3438, preventing the pollen record to be interpreted as a continuous record of the evolution of vegetation and climate occupying a single watershed across HS1. The first phase, i.e. the HS1-a interval (∼18–16.8 ka), is marked by strong occurrences of boreal pollen taxa (especially Picea-Abies). Considering their spatial distribution and the coalescence of the British and Scandinavian ice sheets into the North Sea during the Last Glacial Maximum, these taxa probably originated from the North European Plain, i.e., eastern FM tributaries (east of the Rhine River), where cool-humid conditions generally prevailed. Then, the second phase, i.e. the HS1-b interval (∼16.8–14.7 ka BP), is characterized by a deceleration of the EIS retreat and the drop of boreal pollen values at site MD13–3438 further signing a less influence of the upstream FM drainage system and thus a better characterization of pollen sources related with western FM tributaries. Superimposed to these two HS1 main phases, pollen fluctuations are concomitant with sub-millennial variability in the EIS deglaciation intensity. During the early HS1 (HS1-a), we discuss two short-term increases in the ratio between deciduous trees (Quercus-Corylus-Alnus) and herbaceous plants (Plantago-Amaranthaceae-Artemisia). These events are coeval with phases of increasing dinocyst-based SST seasonality (i.e. through summer SST amplification). We associate these events with lower contribution of the upstream FM catchment as well as, possibly, atmospheric warming and regional sea-level positive oscillations. The HS1-b is composed of three main phases that appear more influenced by the downstream FM drainage system. HS1-b1 (16.8–16.3 ka BP) corresponds to the driest and coldest conditions west of the Rhine River. HS1-b2 (16.3–15.5 ka BP) is coeval with large arrivals of iceberg from the Hudson strait in the Bay of Biscay and thus likely to a major sea-level positive oscillation associated with a phase of FM valley reworking. HS1-b3 (15.5–14.7 ka BP) corresponds to persistent arid conditions that preceded the subsequent more humid conditions recorded from 14.7 ka BP at the start of the Bölling-Alleröd.

位于 Fleuve Manche（FM）古海口附近的一个岩芯（MD13-3438）中的海洋微化石（甲藻胞囊和浮游有孔虫）和基于地球化学（XRF-Ti/Ca）的气候记录显示，在 HS1（∼18-14.7 ka）可能在与欧洲冰盖（EIS）融化率有关的调频机制中发挥了关键作用。在本研究中，我们以 50 年的平均分辨率对 HS1 上的 MD13-3438 花粉含量进行了分析，以检验植被气温是否与面对这种快速气候变异的 SST 相耦合。首先，我们的研究结果强调了 MD13-3438 站点花粉来源的两个主要阶段，这使得花粉记录无法被解释为整个 HS1 单一流域植被和气候演变的连续记录。第一阶段，即 HS1-a 区间（∼18-16.8 ka），北方花粉类群（尤其是松柏类）大量出现。考虑到这些类群的空间分布以及末次冰期英国和斯堪的纳维亚冰原汇入北海的情况，这些类群很可能起源于北欧平原，即 FM 东部支流（莱茵河以东），那里普遍凉爽潮湿。然后，第二阶段，即 HS1-b 区间（16.8-14.7 ka BP）的特征是 EIS 退缩减速，MD13-3438 站点的北方花粉值下降，这进一步表明 FM 上游排水系统的影响减弱，因此与 FM 西部支流相关的花粉来源特征更加明显。与 HS1 的这两个主要阶段相叠加，花粉的波动与 EIS 退化强度的亚千年变化同时发生。在 HS1 早期（HS1-a），我们讨论了落叶乔木（栎树-桉树-欧鼠李树）和草本植物（车前草-马齿苋-蒿草）之间比例的两次短期增长。这些事件与基于二孢子囊的海温季节性增加阶段（即通过夏季海温放大）同时发生。我们认为这些事件与上游调频汇水区的贡献较低有关，也可能与大气变暖和区域海平面正振荡有关。HS1-b 由三个主要阶段组成，似乎受下游调频排水系统的影响较大。HS1-b1（16.8-16.3 ka BP）对应莱茵河以西最干旱、最寒冷的时期。HS1-b2（16.3-15.5 ka BP）与来自比斯开湾哈德逊海峡的大量冰山的到来同时发生，因此很可能是与调频河谷再加工阶段相关的一次重大海平面正振荡。HS1-b3（15.5-14.7 ka BP）与持续干旱的条件相对应，在此之前，从 14.7 ka BP 开始，博林-阿勒罗德开始出现较为潮湿的条件。

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引用次数: 0

Multiple controls on the preservation of organic matter in the lower Mississippian Luzhai Formation black shale in southern China 中国南方密西西比系下统鹿寨组黑色页岩中有机质保存的多重控制因素

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology

Pub Date : 2024-09-19 DOI: 10.1016/j.palaeo.2024.112508

Zeyang Liu , Hui Tian , Bradley B. Sageman , Yaowen Wu , Tengfei Li , Xinyu Wang , Wenpan Cen , Jiyu Chen

The early Carboniferous experienced profound climate cooling that drove the Earth's climate from a mid-Paleozoic greenhouse into the Late Paleozoic Ice Age. Several climate cooling events have been reported, including the Tournaisian and Visean (early to mid-Early Carboniferous). In this study, we perform multi-proxy analyses (organic carbon isotopes, nitrogen isotopes, major and trace elements and organic petrology/geochemistry) of samples from an early Carboniferous section in Nandan region (Guangxi, China). Our goal is to investigate the global carbon‑nitrogen cycle, and associated oceanic productivity and redox perturbations, during a key climatic transition interval, as well as the controls on organic matter enrichment in the sediments. The carbon and nitrogen isotope profiles of the Nandan section record major perturbations during the mid-Tournaisian and early Visean. The mid-Tournaisian carbon isotope excursion (TICE) is marked by a positive δ¹³C_org shift of 1.8 ‰ (from −27.7 ‰ to −25.9 ‰), correlating with a positive δ¹⁵N shift. The early Visean carbon isotope excursion (VICE) is characterized by a positive shift in δ¹³C_org (from −28.2 to −25.5 ‰, with an excursion magnitude of 2.7 ‰), but associated with a negative shift in δ¹⁵N (from +5 ‰ to +4 ‰). The positive δ¹³C_org excursions during these events most likely reflect enhanced organic matter burial with expansion of anoxic seafloor in the global ocean. The drop in nitrogen isotope values in the early Visean is interpreted to be linked with less denitrification under more oxic conditions. The decrease of organic matter contents up section is consistent with the shift to more oxic conditions and increased sedimentary dilution caused by sea-level fall, which is ultimately controlled by orogenic events and climate cooling.

早石炭纪经历了严重的气候变冷，使地球气候从古生代中期的温室气候进入晚古生代的冰河时期。据报道，发生过几次气候变冷事件，包括图尔奈斯期和维西期（早石炭世至早石炭世中期）。在本研究中，我们对南丹地区（中国广西）早石炭世剖面的样品进行了多代理分析（有机碳同位素、氮同位素、主要元素和痕量元素以及有机岩石学/地球化学）。我们的目标是研究在一个关键的气候转变时期的全球碳氮循环、相关的海洋生产力和氧化还原扰动，以及对沉积物中有机物富集的控制。南丹剖面的碳氮同位素剖面记录了图尔奈斯中期和维谢安早期的重大扰动。图尔奈斯中期碳同位素偏移（TICE）的特征是δ13Corg正偏移1.8‰（从-27.7‰到-25.9‰），与δ15N正偏移相关。早期维西期碳同位素偏移（VICE）的特征是δ13Corg的正偏移（从-28.2‰到-25.5‰，偏移幅度为2.7‰），但与δ15N的负偏移（从+5‰到+4‰）相关。在这些事件中，δ13Corg 的正向偏移很可能反映了全球海洋缺氧海底扩张时有机物埋藏的增加。据解释，早期维西期氮同位素值的下降与缺氧条件下反硝化作用减弱有关。上断面有机质含量的减少与海平面下降导致的更多缺氧条件和沉积稀释的增加相一致，而这最终受造山运动和气候变冷的控制。

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引用次数: 0