Sedimentary Geology最新文献

{"title":"Holocene seismically induced soft-sediment deformation structures in the Qingshuihe Basin, northeastern Tibetan Plateau","authors":"Ting Huang ,&nbsp;Zhenhong Li ,&nbsp;Xiaopeng Dong ,&nbsp;Zhonghai Wu ,&nbsp;Linlin Kou ,&nbsp;Fang Wu","doi":"10.1016/j.sedgeo.2025.106902","DOIUrl":"10.1016/j.sedgeo.2025.106902","url":null,"abstract":"<div><div>This study focuses on the extensive development of soft-sediment deformation structures (SSDS) within the Holocene fluvial-lacustrine strata in the central and southern Qingshuihe Basin, located on the northeastern margin of the Tibetan Plateau. Through basin-wide sedimentological analysis, the study systematically examines the development characteristics, formation mechanisms, and triggering factors of SSDS across various sedimentary facies, while also exploring their relationship with regional seismic events.</div><div>The results reveal that a wide variety of SSDS are present in the basin, including small-scale faults, pseudofaults, load structures, water-escape structures, clastic dikes, deformed laminations, tension veins, and mixed accumulations. Most SSDS occur alongside syn-sedimentary faults (small-scale faults or pseudofaults) and exhibit significant directional features. SSDS in fluvial facies are more prominent than those in lacustrine facies, with the former displaying clear stratification, while the latter shows multi-phase deformation. Both fluvial and lacustrine SSDS are closely correlated in stratigraphic position and formation age with tension veins observed in loess deposits on the western side of the basin. Furthermore, the intensity of deformation exhibits a significant negative correlation with the distance from boundary faults. Most SSDS display characteristics of liquefaction, fluidization, and brittle deformation, consistent with seismic shaking.</div><div>Radiocarbon dating of 35 samples and optically stimulated luminescence (OSL) dating of 7 samples indicate that the SSDS in the southern part of the basin (6220 ± 95 a BP to 717 ± 24 a BP) are strongly associated with three major seismic events along the Haiyuan-Liupan Mountain Fault (a paleo-earthquake from 6600 ± 500 a BP to 5640 ± 540 a BP, the 1219 Guyuan M7 earthquake, and the 1306 Guyuan M7 earthquake). Meanwhile, SSDS in the central basin (11,270 ± 1100 a BP to 7728 ± 36 a BP) likely reflect three significant seismic events along the southeastern segment of the Xiangshan-Tianjingshan fault (XS-TJSF). These earthquakes are estimated to have magnitudes ranging from 6.5 to 7.3, with epicenters located in the central region of the southeastern segment of the XS-TJSF.</div><div>This study refines the criteria for identifying earthquake-induced SSDS and provides critical evidence for reconstructing the regional paleo-seismic history, thereby enhancing the understanding of the complex tectonic activity in the area.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"484 ","pages":"Article 106902"},"PeriodicalIF":2.7,"publicationDate":"2025-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144169788","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":"Origin and paleoenvironmental significance of ooids in South China during the Early Triassic hyperthermal climates","authors":"Mengqing Ye ,&nbsp;Bolin Zhang ,&nbsp;Peng Zhu ,&nbsp;Xia Wang ,&nbsp;Xianguo Lang ,&nbsp;Fengcun Xing ,&nbsp;Jingjing Liu","doi":"10.1016/j.sedgeo.2025.106901","DOIUrl":"10.1016/j.sedgeo.2025.106901","url":null,"abstract":"<div><div>The Early Triassic was a crucial period for biotic recovery immediately after the end-Permian mass extinction, with widespread development of ooid deposits around the world. However, two competing hypotheses regarding the inorganic or organic origins of ooids remain under debate. Here, we focus on the Lower Triassic Yelang Formation in the Yunfeng section of Guizhou Province and conduct sedimentological and geochemical analyses, combined with statistical analysis of ooid size and morphology, to reveal the origin of ooids and explore their formation in relation to extreme environmental changes. Our results show that hydrodynamic conditions and microbial activities are key factors influencing ooid formation. The evolution of sedimentary facies, changes in ooid size and types, and variations in ooid morphology and sorting all suggest that stronger hydrodynamic conditions favor ooid formation, leading to more abundant and larger ooid deposits. Low δ¹⁵N values (average +1.51 ‰) suggest flourishing microbes dominated by photoautotrophic nitrogen-fixing cyanobacteria, while the C/N vs. Δ¹³C_carb-org crossplot indicates a significant contribution from eukaryotic algae. Furthermore, microstructural evidence of microbial remains and borings in ooids indicates both constructive and destructive roles of these microbes in their formation. Abundant filamentous microbial fossils and nanograin aggregates observed in ooids also provide direct evidence of biogenic signatures intrinsically related to organomineralization. A comprehensive biochemical model of ooid formation is proposed here, involving microbial-induced mineralization and biomediated carbonate precipitation. In addition, we suggest that the combined effects of exacerbated marine anoxia and extreme hyperthermal climates contributed to the widespread development of ooids during the Early Triassic.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"483 ","pages":"Article 106901"},"PeriodicalIF":2.7,"publicationDate":"2025-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144138759","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":"Middle-Late Pleistocene to Holocene sediments of the Tremithos River and related shallow-marine to non-marine coastal deposits in SE Cyprus: Products of inter-related surface uplift and glacio-eustatic controlled sea-level change","authors":"Christina Antoniou,&nbsp;Alastair H.F. Robertson","doi":"10.1016/j.sedgeo.2025.106900","DOIUrl":"10.1016/j.sedgeo.2025.106900","url":null,"abstract":"<div><div>The Pleistocene development of the Tremithos River exemplifies interacting controls of fluvial and shallow-marine sedimentation. The overall driver was domal uplift of southern Cyprus, focused on the ophiolitic Troodos Massif. Middle-Upper Pleistocene fluvial sediments accumulated under the dominant influences of glacio-eustatic and related climatic changes. Early-Middle Pleistocene is preserved as remnant surfaces and rounded erosional hills. Late Pleistocene-Holocene saw pulsed incision that deepened and narrowed the channel, mainly in the upper reaches. Meanders developed in the middle reaches. A broad, shallow channel formed in the lower reaches, passing into a coastal plain and a broad delta, affected by cyclical marine transgressions and regressions. Following incision events, coarse, poorly sorted conglomerates accumulated under high-energy stream flow in a cool, wet climate, generally correlated with glacial periods. Channel fill was mainly achieved by more persistent, lower energy stream flow in semi-braided channels, coupled with overbank deposition. Common well-rounding of highly resistant lithologies (e.g. chert) within a c. 30 km-long river suggests some recycling from older terrace deposits. Chalky colluvium formed by slope wasting of nearby chalk and marl, mainly during cool, humid periods. Reddish terra rossa paleosols mainly record relatively warm, stable, humid periods. Bedrock lithologies (e.g. diabase, chert) exerted a strong influence on clast lithology and shape. Younger fluvial deposits are coeval with Holocene shallow-marine terrigenous sediments and carbonates (including solitary coral) in coastal areas. Some previously reported shallow-marine sands are reinterpreted as aeolianites. Locally, deposition was influenced by surface uplift along a near-coastal strike-slip fault, related to oblique convergence of the Africa-Eurasia plates.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"486 ","pages":"Article 106900"},"PeriodicalIF":2.7,"publicationDate":"2025-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144562952","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":"Gastropod-rich lacustrine carbonate deposits in N Iberia: a depositional, climatic and ecological record of the Late Miocene","authors":"Zuriñe Larena ,&nbsp;Concha Arenas ,&nbsp;Josep Sanjuan ,&nbsp;Ana Pascual ,&nbsp;Mariano Larraz ,&nbsp;Xabier Murelaga ,&nbsp;Juan Ignacio Baceta","doi":"10.1016/j.sedgeo.2025.106899","DOIUrl":"10.1016/j.sedgeo.2025.106899","url":null,"abstract":"<div><div>The Tortonian Peña Adrian Formation represents the youngest depositional unit of the Miranda-Trebiño basin (Basque-Cantabrian Pyrenees), which developed on the Southern Basque-Cantabrian Pyrenees from late Eocene to Late Miocene times. The formation is a 50–160 m thick succession of alluvial detrital grading to lacustrine carbonates that contain rich and varied calcareous fossil biota (gastropods, ostracods and charophytes). The fossil association characterizes warm temperate, shallow lakes with vegetated bottoms and well‑oxygenated and alkaline fresh waters. Integration of stratigraphic, sedimentological, paleontological and C<img>O stable isotopic data allows the differentiation of a wide range of sedimentary facies, the construction of a depositional model and the definition of distinct evolutionary phases and relation to allogenic processes. Up to 3 metre-thick facies sequences record repetitive water-level changes, likely reflecting short-term climate changes. Overall, the succession outlines an asymmetric cycle of gradual expansion and faster contraction of a shallow ramp-like lake system evolving under oscillating climatic conditions. C and O stable isotopes are consistent with decreasing salinity and increasing precipitation/evaporation balance trough time. Excellent preservation of aragonitic and bimineralic gastropods characterizes the open lacustrine deposits, whereas shell dissolution and neomorphism are distinct in the palustrine ones. This contrasting degree of preservation of calcareous biota clearly reflects changes in the physico-chemical conditions that prevailed during sedimentation and early burial. The findings add to the knowledge of carbonate lake basins, help discern the factors that controlled their evolution and highlight specific depositional and preservation conditions for gastropod-rich carbonate records.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"483 ","pages":"Article 106899"},"PeriodicalIF":2.7,"publicationDate":"2025-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144167723","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":"Impact of secondary geomorphic processes on sedimentary characteristics of alluvial fans: Implications for reservoir exploration and development","authors":"Zixiao Peng ,&nbsp;Jianhua Qu ,&nbsp;En Xie ,&nbsp;Chunqiang Chen ,&nbsp;Bang Zeng ,&nbsp;Dancheng Zhu ,&nbsp;Zhenghong Zhang","doi":"10.1016/j.sedgeo.2025.106892","DOIUrl":"10.1016/j.sedgeo.2025.106892","url":null,"abstract":"<div><div>Alluvial fans, typically characterized by a mixture of fine- and coarse-grained materials, high heterogeneity, and weakly structured organization, are formed through various depositional processes. Fan deposits are considered valuable reservoir exploration targets in the hydrocarbon field worldwide. A series of Quaternary fans in northwestern and northern China, subjected to secondary geomorphological processes of varying degrees, were analyzed. Primary geomorphic processes, characterized by lobe or sheet elements of debris flow, hyperconcentrated flow and sheet floods deposits, generally represent rapid fan aggradation and dominate the sedimentary succession of these fans. Deposition of secondary processes is mainly developed by streamflows reworking with identifiable features, such as sheet-like lag, braided/point bar, and channel elements. A lack of sediment input to the fan and the redistribution and remodification of the primary deposits characterize this process. Synsedimentary reservoir quality is significantly improved by reorganizing sorting, support styles, and bedding structures. The proportion of primary and secondary architectural elements is proposed to evaluate the relative intensity of secondary processes experienced by alluvial fans. The dominant drivers of strong secondary processes are attributed to frequent streamflow events in response to climate changes on millennial timescales. Physical properties and connectivity of alluvial fan reservoirs related to secondary processes are commonly improved compared to reservoirs directly originating from primary processes, as a deep-time example from the Karamay oilfield. The results of this study provide new insights into constructing alluvial fan models in deep-time terrestrial basins and contribute to predicting favorable reservoir distribution and adjusting development strategies for alluvial fan reservoirs worldwide.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"483 ","pages":"Article 106892"},"PeriodicalIF":2.7,"publicationDate":"2025-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143931367","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":"Depositional environment and redox conditions of the Moncorvo Ironstone – Unveiling the evolution of ironstones under Rheic Ocean influence","authors":"Emilio Evo Magro Correa Urbano ,&nbsp;Maria Elisa Preto Gomes ,&nbsp;Carlos Augusto Pinto de Meireles ,&nbsp;Paulo Roberto Gomes Brandão ,&nbsp;João Pedro T.M. Hippertt ,&nbsp;Ricardo Scholz ,&nbsp;Cristiano Lana","doi":"10.1016/j.sedgeo.2025.106885","DOIUrl":"10.1016/j.sedgeo.2025.106885","url":null,"abstract":"<div><div>Ironstones, as key archives of past marine environments, provide invaluable insights into Paleozoic history. Their mineralogy may reflect the physical-chemical conditions of the environment and the nature of available sediments. This study focuses on the Moncorvo Ironstone, a Lower-Middle Ordovician deposit formed during the opening of the Rheic Ocean. Here, we use an integrated approach combining sedimentology, petrology, and geochemistry to constrain the depositional settings and the redox landscape associated with the ironstone deposition. The Moncorvo Ironstone present some unusual characteristics, such as the lack of ooids, an uncommon mineralogy, and a stratigraphic thickness that can reach over &gt;45 m, a remarkable feature for an ironstone. Our investigation reveals that this iron-rich sequence is distributed in two distinct marine environments: an inner shelf and a middle to distal shelf. Each environment has a unique mineral assemblage. Despite the influence of metamorphism and deformation, evidence suggests that much of the mineralogy and texture of this deposit still preserve characteristics of the original sediments. Finally, our findings, alongside a careful assessment of the mineralogy of other ironstones of similar age, suggest a strong stratification of the Rheic Ocean throughout the Early and Middle Ordovician.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"482 ","pages":"Article 106885"},"PeriodicalIF":2.7,"publicationDate":"2025-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143922727","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 forcing of turbidite system on the northern South China Sea margin during the Late Quaternary","authors":"Xuan Zhao ,&nbsp;Wei Li ,&nbsp;Christopher J. Stevenson ,&nbsp;Qiang Zhang ,&nbsp;Shuang Li ,&nbsp;Lingyun Wu ,&nbsp;Zhiyuan Cai ,&nbsp;Xiting Liu ,&nbsp;Wenhuan Zhan","doi":"10.1016/j.sedgeo.2025.106884","DOIUrl":"10.1016/j.sedgeo.2025.106884","url":null,"abstract":"<div><div>Turbidites preserved within sedimentary sequences serve as valuable archives of sea-level and climate fluctuations that influence terrigenous sediment supply and depositional processes. However, a comprehensive understanding of how turbidite systems respond to the complex interplay of external forcing on millennial timescales remains limited. Using grain size, geochemical, and chronological data from two sediment cores in different geomorphic settings, we investigate how turbidite system growth responds to sea level, climate and tectonics along the northern South China Sea (SCS) margin. Core QDN-2, located on the northwestern SCS margin, records two turbidites deposited between 43 ka and 12 ka, followed by a cessation of activity during the Holocene. Conversely, core TXN-1 situated on the northeastern SCS margin, documents frequent turbidity currents since 12 ka. These contrasting records demonstrate that turbidite systems on the northern SCS margin can develop at any sea-level. Our findings reveal that while sea level and tectonics play a role, climate emerges as the dominant external forcing on turbidite system development in the northern SCS. Sufficient climate-induced sediment supply compensates for the influence of interception by the wide shelf and high sea level, providing the necessary material basis for the initiation of turbidity currents. The rapid delivery of terrigenous sediments through turbidity currents facilitates the preservation of these climatic signals within the turbidites. This study highlights the crucial role of climate forcing in turbidite depositional patterns, even on the wide continental shelves, and emphasizes the importance of incorporating climate variability into sequence stratigraphic interpretations.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"482 ","pages":"Article 106884"},"PeriodicalIF":2.7,"publicationDate":"2025-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143916961","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":"Effects of drying on biofilm-mediated sediment stability in intertidal mudflats: transition from biostabilization to biodestabilization","authors":"Ran Ge ,&nbsp;Yonggang Zhao ,&nbsp;Zheng Gong ,&nbsp;Suna Wang ,&nbsp;Aihong Wei ,&nbsp;Mo Peng ,&nbsp;Honglei Liu","doi":"10.1016/j.sedgeo.2025.106883","DOIUrl":"10.1016/j.sedgeo.2025.106883","url":null,"abstract":"<div><div>The presence and growth of biofilms can considerably enhance sediment stability, a phenomenon known as biostabilization. Intertidal mudflats are periodically exposed to air due to tidal cycles. During exposure, they are affected by drying, which may alter the properties of biofilms and then their sediment-stabilizing ability. However, to date, little information is available on this topic. For this, the effects of a biofilm on sediment stability were investigated over a 15-day drying period. The biofilm was obtained by culturing microorganisms isolated from intertidal sediment. Previous studies demonstrate that biofilms enhances sediment stability in two ways. On one hand, biofilms coating on the surface of sediment bed can protect surface sediment from erosion (surface protection), evidenced by an increase in the critical shear stress of sediment. On the other hand, after the detachment of surface biofilms, biofilms growing between sediment particles can hinder the erosion of bottom sediment (hindered erosion), indicated by less amount of sediment eroded following a same erosion event. Results of this study showed that during the drying process, surface protection was initially enhanced but later weakened, while hindered erosion was consistently weakened. By the end of experimental drying trials, the biofilm no longer stabilized sediment; instead, it reduced the stability of surface sediment and promoted the erosion of bottom sediment, leading to biodestabilization. After drying, the structure of the biofilm covering sediment bed became more compact, similar to that of soil crust, whereas the crust-like biofilm was gradually broken towards the end of experimental drying trials. This alteration explains the observed variations in surface protection. The weakened hindered erosion is associated with the loss of adhesion and aggregation of sediment particles as drying progressed. Moreover, many gas bubbles were generated and trapped within dried biofilm and between sediment particles, which possibly increase the buoyancy of biofilm and weaken the inter-particle bonding of sediment particles, thus leading to biodestabilization.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"482 ","pages":"Article 106883"},"PeriodicalIF":2.7,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143845022","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":"Lacustrine sedimentary evidence of cascading mountain hazards at the inner-Alpine Lake Altaussee (Eastern Alps, Austria) during the Late Holocene","authors":"Marcel Ortler ,&nbsp;Jasper Moernaut ,&nbsp;Markus Fiebig ,&nbsp;Andrea Franco ,&nbsp;Jean Nicolas Haas ,&nbsp;Irka Hajdas ,&nbsp;Philipp Haeuselmann ,&nbsp;Julia Rechenmacher ,&nbsp;Lisa-Maria Weber ,&nbsp;Erwin Heine","doi":"10.1016/j.sedgeo.2025.106881","DOIUrl":"10.1016/j.sedgeo.2025.106881","url":null,"abstract":"<div><div>Inner-Alpine or intramountainous lake systems can be formed by glacial, tectonic or landslide processes and typically present complex sediment dynamics that can drastically change over time and can be driven by various natural hazard processes. Their sedimentary archives can therefore provide insights in the past magnitude and frequency of local mountain hazards, which is key for reliable hazard assessment and understanding of mountain landscape evolution. Here we present morphological, seismic-reflection and sedimentary data from Lake Altaussee, a groundwater-fed lake surrounded by steep topography in the Eastern Alps (Austria). The slow organic-rich sedimentation is interrupted by one phase of inflow (by the Augstbach creek), resulting in clastic sediment input between ~1110–1346 cal yr CE. This inflow phase was terminated by an artificial diversion of the creek as documented in historical reports. The combination of large blocks (max. 70 m in diameter), a mass-flow deposit and megaturbidite deposited on deformed basin floor sediments points to multiple terrestrial mass movements with a total volume of ~430,000 m³ that propagated into the lake and which occurred 755–991 cal yr CE. A 3D hydrodynamic model suggests that the potential mass movement at the northern shore induced an impact wave that inundated the western shoreline with flow depth of up to 9 m and reaching up to ca. 210 m inland. Calculated speed of the backflow indicates that coarse shore sediments can be transported into the lake, which can explain the abundance of gravel/coarse sand at the base of the megaturbidite at the periphery of the basin. Moreover, such impact wave would lead to a standing lake water oscillation (seiching), which is further attested by regular lamination and oscillating grain-size parameters at the base of the main silty unit of the megaturbidite. A persistent change in sediment dynamics around a main subaqueous karst spring pit occurred at 165 cal yr BCE–222 cal yr CE when repeated sediment expulsions from the spring pit started to build up a crater rim. This onset of sediment expulsions is directly overlying a soft-sediment deformation structure (micro-faults). A good age correlation of the two major Altaussee events (i: multiple mass movements, ii: onset of sediment expulsions from spring pit) to large mass-transport deposits in the sedimentary record of the nearby Lake Hallstatt let us hypothesize that two large earthquakes took place in the Late Holocene that led to a multitude of morphological and sedimentary responses in the Upper Traun region. Our findings provide the first indication of an impact wave on a natural lake in the Eastern Alps, highlighting the potential for hazard cascades that remain undocumented in historical records, underscoring the need for reassessing natural hazard risks in alpine lake environments.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"482 ","pages":"Article 106881"},"PeriodicalIF":2.7,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143851899","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":"Environmental and oceanographic evolution in the Southern Qiangtang Basin (eastern Tethys) during the latest Pliensbachian to early Toarcian (Early Jurassic)","authors":"Changjun Ji ,&nbsp;Ahmed Mansour ,&nbsp;Yun Chen ,&nbsp;Zhenhan Wu ,&nbsp;Mohamed S. Ahmed ,&nbsp;Wolfgang Ruebsam ,&nbsp;Guoqing Xia","doi":"10.1016/j.sedgeo.2025.106882","DOIUrl":"10.1016/j.sedgeo.2025.106882","url":null,"abstract":"<div><div>The late Pliensbachian-early Toarcian (Early Jurassic) interval is marked by significant climatic changes that affected environmental and paleoceanographic conditions, impacting biogeochemical cycles, as well as marine and terrestrial ecosystems. The most profound environmental changes occurred across the Pliensbachian/Toarcian boundary (P/T B) and in the early Toarcian. Both events align with phases of increased greenhouse gas emissions, global warming, sea-level rises, intensified hydrological cycles, and continental weathering. The Toarcian coincides with the expansion of oxygen-deficient conditions in oceanic and at various shelf areas, marking the Toarcian Oceanic Anoxic Event (T-OAE). In this study, we present high-resolution inorganic geochemical data from the Qixiangcuo section of the Southern Qiangtang Basin, which records both the P/T B and early Toarcian events. The section studied reflects a shallow shelf environment in northeastern part of the Tethys Ocean. Element ratios, such as Ti/Al and Zr/Al, interpreted as sediment grain size proxies, reveal characteristic changes that can be linked to the interplay between sea-level changes and shifts in continental weathering and terrigenous sediment influx. Secular trends in these grain-size proxies reflect sea-level dynamics during the late Pliensbachian-early Toarcian, with notable transgressions at the P/T B and early Toarcian. The early Toarcian event further coincides with increased terrigenous material in response to an intensified hydrological cycle, as evidenced by transient increases in grain-size proxies and higher paleo-weathering indices (e.g., ln(Al₂O₃/Na₂O)). Despite the increased nutrient flux to the paleo-shelf sea, enrichment factors (EF) of productivity proxies (Zn_EF, Cu_EF, Ba_EF, Ni_EF) do not show increases in organic matter export to the sediments. Thus, organic matter-lean sediments (total organic carbon &lt;0.5 wt%) have accumulated in the Southern Qiangtang Basin during the latest Pliensbachian-early Toarcian. The lack of enrichment in redox-sensitive elements, such as Mo, V, and U in the sedimentary rocks of the Qixiangcuo section, points to a well‑oxygenated environment. Accordingly, although the T-CIE is identified in the study section, the T-OAE did not develop in this paleogeographic area. The new data thereby highlight the role of local-regional paleoenvironmental and paleoceanographic parameters as important factors contributing to the genesis of the T-OAE and the burial of organic carbon in marine sediments.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"482 ","pages":"Article 106882"},"PeriodicalIF":2.7,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143823730","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}