Sedimentary Geology最新文献

{"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}

{"title":"Sequence architecture of a Miocene marginal shelf sea influenced by tectonic activity: A case study of Eastern Yinggehai Basin, South China Sea","authors":"Zhen Wang ,&nbsp;Benzhong Xian ,&nbsp;Qian Ma ,&nbsp;Caiwei Fan ,&nbsp;Jianping Liu ,&nbsp;Qianran Wu ,&nbsp;Rongheng Tian ,&nbsp;Hui Li ,&nbsp;Ximeng Zhang ,&nbsp;Wenmiao Zhang","doi":"10.1016/j.sedgeo.2025.106879","DOIUrl":"10.1016/j.sedgeo.2025.106879","url":null,"abstract":"<div><div>While sequence stratigraphic frameworks of passive continental margins have been extensively studied, their counterparts in semi-enclosed marginal shelf seas remain poorly understood. This study investigates the sequence architecture and depositional patterns of a marginal shelf sea system through integrated analysis of 3D seismic, well-log, and core data from the Miocene succession in the Yinggehai Basin, South China Sea. The Miocene strata were subdivided into seven third-order sequences whose architectures and sedimentary associations were governed by the interplay between slope-break geometries, sea-level fluctuations, and sediment supply. Three distinct shelf sequence types (A1, A2, and B) were recognized based on spatial configurations of slope breaks and relative sea-level positions. Type A1 sequence (Huangliu Formation and Mei1 Member) consists of multiple slope breaks at basin margins and in the interior basin, with sea-level falls exceeding the elevation of interior slope breaks. The sequence preserves complete systems tracts, including early lowstand (gravity flow-dominated), late lowstand, transgressive, and highstand tracts. In contrast, Type A2 sequence (Mei2 Member), though retaining multiple slope breaks, lacks early lowstand systems tracts due to insufficient sea-level fall to expose interior slope breaks. Type B sequence (Sanya Formation) features solely basin-margin fault-controlled slope breaks and shares systems tract compositions with Type A2. Sedimentary processes vary markedly among sequence types. Type A1 sequence hosts multi-phase, large-scale gravity flow deposits encompassing submarine fans, slope-perpendicular channels, and slope-parallel channels, with maximum development during early lowstand conditions. Type A2 sequence is characterized by braided river deltas interfingering with shelf mudstones, accompanied by limited gravity flow activity. Type B sequence comprises shallow marine facies and small-scale braided deltas. Hydrocarbon implications emerge from the preferential occurrence of reservoir-quality gravity flow sands in Type A1 lowstand systems tracts, while regional seals and source rocks are associated with shelf mudstones in Type A2 and B sequences. The sequence evolution is primarily controlled by <em>syn</em>-depositional tectonics (fault reactivation, post-rift subsidence) and semi-enclosed paleogeomorphology, secondarily by sediment influx and eustasy. This framework advances predictive models for shelf-scale sequence development in restricted marine settings and provides critical insights for global hydrocarbon exploration in analogous basins.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"482 ","pages":"Article 106879"},"PeriodicalIF":2.7,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143807564","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":"Types and formation mechanisms of authigenic quartz in the Late Paleozoic alkaline lacustrine shales, NW China","authors":"Changzhi Li ,&nbsp;Zhiming Li ,&nbsp;Pei Guo ,&nbsp;Jian Wang ,&nbsp;Wangwei Liu ,&nbsp;Baozhen Zhang ,&nbsp;Meiyuan Song ,&nbsp;Kai Zhong ,&nbsp;Jinghong Xu","doi":"10.1016/j.sedgeo.2025.106880","DOIUrl":"10.1016/j.sedgeo.2025.106880","url":null,"abstract":"<div><div>Authigenic quartz controls the storage and mechanical properties of shales, and has attracted a growing attention in marine and continental shales. The silica solubility in alkaline lakes is high due to the high lake water pH (&gt;9) and thus alkaline lacustrine shales generally contain abundant authigenic quartz. However, the occurrences and formation of authigenic quartz in alkaline lacustrine shales and its impact on shales remain poorly studied. To solve these problems, we systematically studied the Late Paleozoic alkaline lacustrine Fengcheng Formation in the Mahu Sag of the Junggar Basin via optical microscope and scanning electron microscope observations and elemental analyses. Four types of authigenic quartz have been identified in the Fengcheng Formation (shales): chert nodules or bands, matrix-dispersed microquartz, mineral-replacive quartz, and veins-filling quartz. The Fengcheng Formation shales contain excess SiO₂ ranging from 11.3 % to 60.4 % based on element calculation and matrix-dispersed microquartz is the dominant type of authigenic quartz, followed by cherts. Cherts and matrix-dispersed microquartz were formed during syndepositional to early diagenetic stage, sourced from pH-driven dissolution of detrital quartz grains and transformation of volcanic materials in highly alkaline water. Both chert and matrix-dispersed microquartz formation can increase the rock strength of shales while matrix-dispersed microquartz can also form massive intercrystalline pores and protect the micropores from compaction. In contrast with marine and non-alkaline lacustrine siliceous shales, alkaline lacustrine shales have a higher abundance and more formation stages of authigenic quartz, and can form high-quality shale reservoirs with high contents of organic matter and authigenic quartz in shallow-water zone.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"482 ","pages":"Article 106880"},"PeriodicalIF":2.7,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143823729","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":"The Balanoglossites ichnofabrics in the aftermath of the Permian-Triassic mass extinction","authors":"Pengbing Yan ,&nbsp;Xueqian Feng ,&nbsp;Shiwei Shang ,&nbsp;Zhong-Qiang Chen ,&nbsp;He Zhao ,&nbsp;Ding Zhou ,&nbsp;Zijie Zheng ,&nbsp;Zemin Zheng","doi":"10.1016/j.sedgeo.2025.106877","DOIUrl":"10.1016/j.sedgeo.2025.106877","url":null,"abstract":"<div><div>Trace fossils are widely distributed in pre-extinction Permian successions, and are also relatively common in the Lower Triassic strata. They have been used for evaluating the recovery process of marine infaunal ecosystem following the Permian-Triassic (P-Tr) mass extinction. However, one complicated ichnogenus <em>Balanoglossites</em> has not been clearly recognized and described in the Early Triassic previously, and its importance in revealing biotic recovery in the aftermath of the P-Tr mass extinction has not been evaluated. Here we documented <em>Balanoglossites</em> ichnofabrics from the Lower Triassic Yongningzhen Formation of the Yongningzhen section from Guizhou Province, South China. <em>Balanoglossites</em> is characterized by three-dimensional complex burrow system with Y-shaped and J-shaped galleries and multiple openings, and the herein described form is assigned to <em>B. triadicus</em>. Microstructures of <em>Balanoglossites</em> under SEM and EDS revealed oxidized pyrite framboids occurred merely near the burrow wall, which may be related to activities of the trace maker and symbiotic microorganism such as sulphate-reducing bacteria. Raman spectrum mapping showed that organic matter was enriched along the burrow boundaries of <em>Balanoglossites</em>, but was lacking in the burrow fill. This pattern may result from the impregnation of the burrow walls with organic mucus and bioirrigation by the trace maker. Polychaetes are considered as the most possible trace makers of <em>Balanoglossites</em>, and they were opportunistic pioneers that proliferated in the Early Triassic. The low ichnodiversity of <em>Balanoglossites</em>-bearing strata contrasts with coeval ichnoassemblages, which probably results from intense bioturbation by deeper-tier burrows that prevents the preservation of surficial to shallow-tier trace fossils. Although <em>Balanoglossites</em> is a complex burrow, its occurrence in the Early Triassic is not an indicator of the full recovery of infaunal ecosystem.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"481 ","pages":"Article 106877"},"PeriodicalIF":2.7,"publicationDate":"2025-03-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143785527","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":"Integrated investigation of rare earth elements, molecular fossils, and stable isotopes in drill cores from deep-buried strata in the Yangtze Block: Implications for the Early Cambrian sedimentary environments","authors":"Moïse Luemba ,&nbsp;Zhonghong Chen ,&nbsp;Zhi Chai ,&nbsp;Yong Chen ,&nbsp;N'nahano-Ruhindwa Heritier ,&nbsp;Raphael Matamba","doi":"10.1016/j.sedgeo.2025.106878","DOIUrl":"10.1016/j.sedgeo.2025.106878","url":null,"abstract":"<div><div>Geological records of the Lower Paleozoic indicate the co-occurrence of large-scale geo- and bio-events, including the diversification of marine complex life and widespread phosphogenesis, making the Early Cambrian aquatic environments a long-standing subject of global interest. Despite extensive research, the interplay between paleoclimate, continental chemical weathering, seawater redox conditions, and salinity during the Cambrian Explosion remains debated. To address this, we conducted geochemical analyses (e.g., XRF, ICP-MS, MRM GC–MS, and IRMS) and optical microscopy on drill cores from the Early Cambrian deep-buried strata (&gt;4 km depth) in an intrashelf basin within the Yangtze Block. Geochemical proxies, including pronounced negative cerium anomalies (as low as 0.20) and a positive pristane-to-phytane ratio excursion, indicate an expansion of oxic waters between ∼531 and 526 Ma, while widespread anoxic conditions prevailed around 531 and 526 Ma. Climate fluctuations between arid and humid periods are inferred from major elements (e.g., Al, Fe, Mn), trace element ratios (e.g., Rb/Sr, Sr/Cu), and rare earth element parameters (e.g., ΣLREE/ΣHREE, Y/Ho). High gammacerane index values (up to 0.41), the presence of <em>β</em>-carotene, elevated Sr/Ba ratio, and <em>δ</em>^<em>18</em><em>O</em> values (up to −4.87 ‰) suggest periods of high salinity and evaporative conditions during arid phases. Organic geochemical signatures, including a high carbon preference index (CPI &gt; 1) and highly negative <em>δ</em>^<em>13</em><em>C</em> values (&lt;−24 ‰), indicate a biological origin of organic matter, with measurable 2-methylhopane (up to 2.48 %) and 4-methylsterane indices (up to 20 %) suggesting contributions from primary producers such as cyanobacteria, alphaproteobacteria, and dinoflagellates. The co-occurrence of oxygenated, highly saline, and evaporative Ca-P-rich waters with the diversification of small shelly fossil assemblages (SSFs 2 and 3) suggests that the studied intrashelf basin provided a favorable setting for the emergence and diversification of complex life. These findings offer new insights into the paleoenvironmental conditions that shaped marine ecosystems during the Cambrian radiation.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"481 ","pages":"Article 106878"},"PeriodicalIF":2.7,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143768891","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}