Palaeogeography, Palaeoclimatology, Palaeoecology最新文献

{"title":"Monsoon and deep ocean control of organic carbon burial in the southeastern Bay of Bengal","authors":"Jingrui Li ,&nbsp;Shengfa Liu ,&nbsp;Hui Zhang ,&nbsp;Xiaoming Miao ,&nbsp;Fangliang Li ,&nbsp;Kun Guo ,&nbsp;Hongying Song ,&nbsp;Rijun Hu ,&nbsp;Rui Jiang ,&nbsp;Somkiat Khokiattiwong ,&nbsp;Narumol Kornkanitnan ,&nbsp;Xuefa Shi","doi":"10.1016/j.palaeo.2025.113163","DOIUrl":"10.1016/j.palaeo.2025.113163","url":null,"abstract":"<div><div>Marginal seas play a key role in absorbing anthropogenic CO₂, yet drivers of their glacial-interglacial carbon burial remain controversial, especially in deep water. The Bay of Bengal—a global carbon sequestration hotspot—exhibits unresolved spatial heterogeneity, with the southeastern region dominated by marine organic carbon and invaded by deep-ocean waters. Here, we reconstruct organic carbon burial history since the Last Glacial Maximum (LGM) using total organic carbon content (TOC) and isotopes (δ¹³C_org), and discuss their controlling mechanisms by reconstructing paleoproductivity, redox condition and bottom water dynamics using multi-proxy records (authigenic neodymium isotopes and uranium content, biogenic barium content). The organic carbon accumulation rate peaked during the LGM (0.75 % TOC; 200 mg cm⁻² kyr⁻¹) due to enhanced monsoon-driven vertical mixing and oxygen-depleted preservation, then declined to minimal values in the Holocene (0.21 % TOC; 27 mg cm⁻² kyr⁻¹) with enhanced bottom-water oxygenation. These shifts support a “mixing‑oxygenation” mechanism: monsoon intensity governs surface productivity and particle export, while deep-water intrusions regulate oxygen levels and the efficiency of carbon preservation. Our findings highlight the critical role of coupled surface-deep ocean processes in regulating ocean carbon sinks, and contribute to improved understanding and prediction of organic carbon burial processes in marginal sea-ocean transition zones under future global warming and intensified oceanic hypoxia.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"676 ","pages":"Article 113163"},"PeriodicalIF":2.6,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144711787","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Climate, not transport from “uplands” or “extrabasinal lowlands,” is the cause of drought-tolerant terrestrial organisms in the late Paleozoic fossil record","authors":"William A. DiMichele ,&nbsp;Robert A. Gastaldo ,&nbsp;Spencer G. Lucas ,&nbsp;Hermann W. Pfefferkorn","doi":"10.1016/j.palaeo.2025.113160","DOIUrl":"10.1016/j.palaeo.2025.113160","url":null,"abstract":"<div><div>A long-standing interpretation of the Pennsylvanian “Coal Age” tropical landscape partitions it along an elevational gradient, with wetland, drought-intolerant plants and animals occupying lowland, basinal settings, and increasingly drought-tolerant plants and animals colonizing progressively more remote areas, termed “extrabasinal lowlands” and “uplands”. This model embodies the unspoken, and long-held assumption of a broad, uniform climate across the tropics (warm and wet). The landscape environmental gradient is envisioned as the result of increasing soil drainage with distance from the shoreline and elevation. Consequently, drought-tolerant organisms found in basinal lowlands are, for the most part, assumed to have been transported there from their spatially remote habitats. Here we review a more recent model that incorporates the glacial dynamics of the Pennsylvanian Subperiod in Earth history. Changes in polar ice volume during glacial-interglacial cycles were accompanied by synchronous changes in sea level, atmospheric circulation and attendant climates, and sedimentary dynamics. In tropical basins this resulted in periods of high moisture and low seasonality, producing widespread wetlands with drought-intolerant organisms (high preservation potential), alternating with high-seasonality and variable moisture landscapes populated by organisms tolerant of seasonal dryness and drought (lower preservation potential). Seasonally dry landscapes included wetland forms persisting in wet sub-habitats, or confined to refugia. This latter Climate Model encompasses the full suite of biological, geological, and modeling results better than the unidimensional Upland Model and thus has far greater explanatory potential for the fossil record.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"676 ","pages":"Article 113160"},"PeriodicalIF":2.6,"publicationDate":"2025-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144703331","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spatial evolution of westerly jets over East Asia since the Last Glacial Maximum: A Mariana Trench record","authors":"Yanning Wu ,&nbsp;Yifeng Liu ,&nbsp;Tao Wu ,&nbsp;Chun-Feng Li ,&nbsp;Wancang Zhao ,&nbsp;Taoran Song ,&nbsp;Liyan Tian","doi":"10.1016/j.palaeo.2025.113162","DOIUrl":"10.1016/j.palaeo.2025.113162","url":null,"abstract":"<div><div>Variations in the seasonal south-to-north transition of the westerly jet (WJ) relative to the Tibetan Plateau have been suggested to control the paleoclimate change over Asia. To improve the understanding of variations in the seasonal WJ transition since the Last Glacial Maximum (LGM), we examine the changes in the provenance of Asian dust in the sediments from the southern Mariana Trench using trace element compositions and Sr-Nd isotopic signatures. During the LGM with low Northern Hemisphere summer insolation, the WJ axis remained south of the Tibetan Plateau throughout the year. The southern Mariana Trench received dust from the Taklimakan Desert during most of the LGM period. However, it mainly received dust from the Mongolian Gobi Desert during some periods in the early LGM. We attributed this dust source variation to the increased Northern Hemisphere ice volume and concomitant shrinkage of the area affected by the WJ during the LGM. This dust source variation may also account for higher dust accumulation rates during the early LGM in the North Pacific Ocean than during the late LGM. As the boreal summer insolation decreased after the mid-Holocene, the timing of the seasonal WJ transition was progressively delayed, and the orientation of the jet axis shifted from southwest-northeast to west-east. We emphasize that the spatiotemporal difference in the Asian precipitation since the LGM was closely associated with the variations in the seasonal jet transition.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"676 ","pages":"Article 113162"},"PeriodicalIF":2.6,"publicationDate":"2025-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144696884","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Early to Middle Permian fusulinids from the northern Changning-Menglian Belt, western Yunnan, China: Taxonomic features and insights for Tethyan paleogeography","authors":"Hao Huang ,&nbsp;Xiaochi Jin ,&nbsp;Jianbin Zheng ,&nbsp;Zhen Yan","doi":"10.1016/j.palaeo.2025.113153","DOIUrl":"10.1016/j.palaeo.2025.113153","url":null,"abstract":"<div><div>The Changning-Menglian Belt in western Yunnan, China, which hosts probable seamount-related limestones, represents a key Tethyan suture in Asia. Fusulinids in these limestones are both age- and environment-sensitive, and thus offer insights into this belt's complex paleogeography and the hitherto understudied benthic faunas within the pelagic Tethys. This study presents late Early to Middle Permian fusulinids from the northern part of this belt, mainly collected from the Lizishu Section. Key taxa in these collections, notably <em>Neoschwagerina brevis</em> and <em>N. margaritae</em>, indicate a Roadian-Capitanian age. Furthermore, qualitative and quantitative comparison, including cluster and network analysis, reveal that Middle Permian fusulinids in this belt exhibit the highest Jaccard similarity with those of the peri-Gondwana Baoshan Block, whereas Early Permian fusulinids of this belt show closer affinity to coeval ones from Cathaysian South China. The reduced connectivity between this belt and South China differs markedly from the enhanced similarities between the peri-Gondwana and Cathaysian regions from the Early to Middle Permian. This pattern suggests that the limestone successions now preserved in this belt probably represent carbonate caps of seamounts generated at different ages within the Tethyan Ocean. The carbonates of mainly Middle Permian ages likely were situated farther from equatorial South China than their Early Permian counterparts. Specifically, the Middle Permian fusulinids of this belt may inhabit paleolatitudes akin to those of the Baoshan Block, considerably higher than Cathaysian and western peri-Gondwana localities. These findings underscore the unique role of seamounts as dynamic habitats for fusulinids and paleogeographic markers in the Tethyan Ocean.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"676 ","pages":"Article 113153"},"PeriodicalIF":2.6,"publicationDate":"2025-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144696887","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Benthic Foraminiferal recovery following a massive Submarine Landslide in the Laxmi Basin, Arabian Sea (IODP U1457)","authors":"Thulasi Thena ,&nbsp;Nisha Nair ,&nbsp;Dhananjai Kumar Pandey","doi":"10.1016/j.palaeo.2025.113150","DOIUrl":"10.1016/j.palaeo.2025.113150","url":null,"abstract":"<div><div>Submarine mass transport deposits (MTDs) are sedimentary deposits formed by transporting large amounts of sediment downslope, usually in a marine setting. Evidence of such deposits was found in the Laxmi Basin, Arabian Sea, during the International Ocean Discovery Program (IODP) Expedition 355. The MTDs of the Laxmi Basin include matrix-supported carbonate breccia, reworked Indus-derived sediment, material from western Indian rivers, and some from the Deccan Traps. It is estimated to have occurred during the Late Miocene period (∼11 to 9 Ma). The diverse sediment sources suggest that the region had undergone significant sedimentary loading, contributing to instability. In this study, we conducted foraminiferal analysis to examine the benthic foraminiferal groups within MTDs to gain insights into the environmental conditions during deposition and subsequent reworking. Benthic foraminiferal communities in MTDs show reduced diversity and altered abundance compared to undisturbed sediments in the region, reflecting the stress and rapid deposition associated with mass transport events. The specific group of species belonging to <em>Cibicidoides</em>, <em>Epistominella</em>, <em>Gavelinopsis</em>, and <em>Oridorsalis</em> taxa struggled to exist due to changes in sediment texture, which further primed variation in the organic matter affecting the foraminiferal food sources. The benthic foraminifera, which were considered as oxygen minimum zone (OMZ) taxa were buried, leaving behind broken fragments during the event and affecting the region's abundance, diversity, and community structure. The bottom water oxygen estimated in these sediments was less than 0.7 mL/L, revealing the dysoxic conditions that altered the sediment nutrient distribution during deposition. The diversity index shows a significant decrease during MTD, indicating that the benthic foraminiferal community is experiencing gradual recovery or shifts in species composition over time. This process is characterized by succession, where pioneer species colonize the new sediments before a more stable community establishes itself. Despite the challenges, the foraminiferal and geochemical proxies demonstrate the importance of understanding the paleoenvironmental impacts associated with MTD.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"676 ","pages":"Article 113150"},"PeriodicalIF":2.6,"publicationDate":"2025-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144696886","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Paleoecology and paleoclimate across the Early Cretaceous Xing'anling Group: New palynological and radiometric data from the Hailar Basin (NE China)","authors":"Yan Zhang ,&nbsp;Iván R. Barreiro ,&nbsp;Chuan-biao Wan ,&nbsp;Yue-wu Sun ,&nbsp;Wen-chun Ge ,&nbsp;Yun-fei Xue ,&nbsp;Ti Li ,&nbsp;Xin Zhang ,&nbsp;Chun-yang Bu ,&nbsp;Hao Zhu","doi":"10.1016/j.palaeo.2025.113156","DOIUrl":"10.1016/j.palaeo.2025.113156","url":null,"abstract":"<div><div>The Early Cretaceous marked a dynamic interval in the evolution and distribution of terrestrial floras, coinciding with significant climatic and tectonic reorganization. In China, widespread continental deposits from this period have yielded rich palynofloras that offer insights into vegetation dynamics and paleoclimate patterns across eastern Eurasia. Among these basins, the Hailar Basin in northeastern China is notable for its extensive, continuous sedimentary succession exceeding 6000 m, which preserves a detailed record of terrestrial environments. Well HD4, drilled within the Hongqi Sag of the basin, captures the most complete Early Cretaceous succession documented to date. This section comprises a transition from coarse-grained alluvial and fluvial to fine-grained lacustrine deposits, assigned to the Xing'anling Group (Tongbomiao and Nantun formations). This study presents new palynological data from Well HD4, supplemented by zircon U–Pb ages from adjacent volcanic layers, allowing the differentiation of three palynological assemblages spanning the Berriasian to early Barremian. These biostratigraphic inferences align well with new LA–ICP–MS zircon U–Pb dates from both formations. Changes in floral composition reflect a shift from megathermal, <em>Cycadopites</em>–dominated assemblages to more temperate, conifer-rich communities with increasing proportions of ferns and bryophytes. This transition likely signals environmental stabilization and a slight cooling trend. Despite this turnover, the vegetation throughout the section remained adapted to humid conditions, in line with the expansion of lacustrine systems and progressive basin subsidence during the transition from the Tongbomiao to the Nantun formations.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"676 ","pages":"Article 113156"},"PeriodicalIF":2.6,"publicationDate":"2025-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144703329","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Terminal pleistocene organic carbon anomaly in Lake Biwa sediments linked to potential anthropogenic fires: Implications for early human impact on large lake systems","authors":"Jun Inoue ,&nbsp;Toko Tanaka ,&nbsp;Maiko Ikegami","doi":"10.1016/j.palaeo.2025.113159","DOIUrl":"10.1016/j.palaeo.2025.113159","url":null,"abstract":"<div><div>Lacustrine sedimentary records serve as valuable archives for reconstructing past fire histories and associated limnological changes. Lake Biwa, the largest freshwater lake in Japan, displays a distinct anomaly in total organic carbon (TOC) concentrations around 13 ka, the origin of which remains uncertain. Previous studies have proposed a potential link between this anomaly and elevated charcoal concentrations, suggesting intensified fire activity. However, the precise temporal relationship between these phenomena remains unclear. In this study, we conducted continuous, high-resolution analyses of TOC contents and charcoal concentrations from sediment cores to investigate their association. Our results reveal a clear synchrony between the TOC anomaly and heightened charcoal concentrations around 13 ka. Quantitative analysis indicates that the direct contribution of charcoal to TOC is negligible. We propose that frequent fire activity during this period likely destabilized soils, enhancing the influx of terrestrial organic matter into the lake and driving the observed TOC anomaly. Notably, the timing of increased fire activity coincides with the earliest evidence of human settlement in the region. Given the absence of similarly elevated charcoal concentrations at other times, our findings suggest that these fires were likely anthropogenic. This study provides one of the earliest potential examples of human-induced impacts on large freshwater lake ecosystems.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"676 ","pages":"Article 113159"},"PeriodicalIF":2.6,"publicationDate":"2025-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144703327","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Devonian–Triassic tectonic evolution of the Western Qinling Orogenic Belt of central China: Insights from detrital zircon UPb chronology and rock geochemistry","authors":"Yan Zhang ,&nbsp;Shuang Dai ,&nbsp;Futian Liu ,&nbsp;Dongbao Guo ,&nbsp;Lingfeng Qin ,&nbsp;Zhongzhao Ding ,&nbsp;Yongfa Chen ,&nbsp;Xinnan Fang ,&nbsp;Xiaojun Ma ,&nbsp;Yu Wang ,&nbsp;Hua Li","doi":"10.1016/j.palaeo.2025.113155","DOIUrl":"10.1016/j.palaeo.2025.113155","url":null,"abstract":"<div><div>Analysis of the Palaeozoic tectonic evolution of the Western Qinling Orogenic Belt (WQOB) is important for understanding the development of the eastern segment of the Paleo-Tethys domain. In this paper, U<img>Pb zircon chronology and rock geochemistry of Devonian-Triassic strata in the WQOB are analyzed to shed light on the tectonic evolution of this region. Comparison of age spectra reveals that the WQOB had a significant detrital source from the northwest margin of the Yangtze Block in Early Devonian times. However, during Middle Devonian-Carboniferous times, the Middle Qilian and North Qinling orogens became the dominant source areas. A further transition occurred in Permian to Middle Triassic times when detrital sources originated from the southwest margin of the North China Block, and in late Triassic times, mixed sourcelands prevailed including the northern margin of the North China Block and the east of Middle Qilian Orogen. Based on our geochemical analysis, we identify a Devonian-Carboniferous tectonic context characterized by a stable passive continental margin, and a Permian-Triassic tectonic period involving evolution towards an unstable active continental margin. The detrital zircon age spectrum characteristics and geochemical results support the view that the Shangdan Ocean had closed before the Early Devonian and the Mianlue Ocean closed during the Late Triassic.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"676 ","pages":"Article 113155"},"PeriodicalIF":2.6,"publicationDate":"2025-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144696883","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Insights into the Cretaceous-Paleogene boundary in Central Anatolia, Turkey: A comprehensive multi-proxy study","authors":"A. Uygar Karabeyoğlu ,&nbsp;Thierry Adatte ,&nbsp;Valentin Lorenzo ,&nbsp;Jorge E. Spangenberg ,&nbsp;Eric Font","doi":"10.1016/j.palaeo.2025.113149","DOIUrl":"10.1016/j.palaeo.2025.113149","url":null,"abstract":"<div><div>The Mudurnu-Göynük Basin, Central Anatolia, Turkey, hosts a complete record of the Cretaceous-Paleogene transition. Two stratigraphic sections, Göynükw and Okçular, were logged at high resolution and analyzed using micropaleontological, mineralogical, and geochemical methods. The micropaleontological analysis allowed the identification of the uppermost Maastrichtian planktonic foraminiferal biozone CF1 (<em>Plummerita hantkeninoides</em>) and the lowermost Danian biozones P0, Pα, P1a, P1b, and P1c. The Cretaceous-Paleogene boundary (KPB) at both sites corresponds to a sharp extinction of the large, ornate planktonic foraminifera (e.g., <em>Globotruncana</em>, <em>Racemiguembelina</em>, <em>Planoglobulina</em>), negative shifts in carbon and oxygen isotope ratios (δ¹³C_carb and δ¹⁸O_carb), decreases in calcite and smectite contents, increases in quartz, phyllosilicates, kaolinite and illite contents, peaks in mercury (Hg), tellurium (Te) and trace element contents. Furthermore, magnetic susceptibility values decrease continuously throughout the Maastrichtian CF1 Zone, and this decrease even accelerates before the KPB, coinciding with an increase in Hg and Te contents. This accelerated decline in magnetic susceptibility values may correspond to one of the major Deccan eruptions that formed the Poladpur Formation. The new dataset suggests that environmental change began in the uppermost Maastrichtian and culminated in the KPB. The total ecosystem recovery may have occurred a few hundred thousand years after the KPB, as supported by the reappearance of the larger planktonic foraminifera and δ¹³C_carb values similar to those before the KPB.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"676 ","pages":"Article 113149"},"PeriodicalIF":2.6,"publicationDate":"2025-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144703330","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Strong coupling between the carbon and nitrogen cycles, environmental change, and organic carbon enrichment during the early–middle Eocene","authors":"Chuan Xu ,&nbsp;Guangrong Peng ,&nbsp;Pei Liu ,&nbsp;Ye He ,&nbsp;Peimeng Jia ,&nbsp;Xuanlong Shan ,&nbsp;Guoli Hao ,&nbsp;Mengrong Shen ,&nbsp;Kang Li","doi":"10.1016/j.palaeo.2025.113145","DOIUrl":"10.1016/j.palaeo.2025.113145","url":null,"abstract":"<div><div>The early–middle Eocene constitutes a key stage of the Phanerozoic because it represents the last long-lived greenhouse period in Earth's history. The identification of the mechanisms underlying the associated geochemical carbon and nitrogen cycles can help us understand the environmental effects of global warming during the early–middle Eocene. There is currently notable interest in marine systems, but little is known regarding the geochemical cycling of carbon and nitrogen in lake systems during the early–middle Eocene. To address this problem, we systematically analyzed carbon and nitrogen isotopes in organic-rich lacustrine mudstones of the lower–middle Eocene Wenchang Formation in the Pearl River Mouth Basin (South China). We then determined the paleoclimate disturbances and historical paleoenvironmental information recorded in the sediments and established a conceptual environmental and biogeochemical model of the Wenchang Formation on the basis of the carbon and nitrogen cycles. The carbon isotope data revealed that the geochemical carbon cycle was affected mainly by the concentration of dissolved CO₂ and input from chemoautotrophs in lake water and that negative δ¹³C_org values provide evidence for positive feedback to the warm paleoclimate and high atmospheric <em>p</em>CO₂ levels during the early–middle Eocene. Enhanced chemical weathering promoted an increase in primary productivity and intensified the lacustrine reducing environment, thereby forming a feedback loop between productivity and hypoxia. This mechanism driving the warm and humid climate was particularly significant in Units I and III of the Wenchang Formation. With decreasing atmospheric <em>p</em>CO₂ level, the positive excursions of δ¹³C_org suggest the existence of a cooling interval in the climate (during the deposition of Units II and IV). A salinization event led to the occurrence of an anoxic and brackish water column under the influence of a strongly restricted environment during these periods, while the positive excursion of δ¹⁵N suggested an increased denitrification rate. The positive excursions of δ¹⁵N and δ¹³C_carb were significantly associated with increasing total organic carbon (TOC) contents, which suggests that the increase in nitrate concentration was synchronous with the intensification of the lacustrine reducing environment and the increase in bioproductivity. Elucidating the strong coupling among the carbon and nitrogen cycles, environmental changes, and organic carbon enrichment during the early–middle Eocene can provide key constraints for understanding the mechanisms driving the carbon and nitrogen cycles and organic matter enrichment in lakes during the paleoclimate warming period.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"676 ","pages":"Article 113145"},"PeriodicalIF":2.6,"publicationDate":"2025-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144696970","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}