Journal of Palaeogeography最新文献

{"title":"Genesis of carbonate concretions in Early Silurian shales of the Upper Yangtze area: Multi-phase constraints from deposition to diagenesis","authors":"Lei Chen,&nbsp;Shuai-Cai Wu,&nbsp;Xiu-Cheng Tan,&nbsp;Min Xiong,&nbsp;Xin Chen,&nbsp;Guan-Bao Ren,&nbsp;Chong-Jie Liao,&nbsp;Zhen-Xiang Yu,&nbsp;He-Xin Qin,&nbsp;Xue-Ying Wang","doi":"10.1016/j.jop.2026.100393","DOIUrl":"10.1016/j.jop.2026.100393","url":null,"abstract":"<div><div>Abundant carbonate concretions in Early Silurian Longmaxi Formation shales of the Upper Yangtze archive key paleoenvironmental and diagenetic information. In this study we integrate petrography, inorganic geochemistry and carbon–oxygen isotopes to constrain their origin. The concretions are dominated by low-Mg calcite with minor dolomite, pyrite and diagenetic barite. Moderately ¹³C-depleted carbonate (δ¹³C = −10.7‰ to −14.7‰) and paleotemperatures of 64–66 °C indicate early-diagenetic formation at shallow burial within the sulfate reduction zone (SRZ) and overlying sulfate–methane transition zone (SMTZ). These signatures and associated geochemical data show that dissolved inorganic carbon (DIC) was mainly supplied by organoclastic sulfate reduction (OSR) and sulfate-driven anaerobic oxidation of methane (SD-AOM). Core–rim elemental zoning records dominantly concentric growth with subordinate pervasive pore-filling cementation. Rare-earth element (REE) patterns distinguish volcanic Eu anomalies in Hirnantian–Rhuddanian host shales from subtler Eu–Yb anomalies in Aeronian concretions, consistent with modification by reducing Fe-rich pore fluids rather than by basin-wide hydrothermal overprint. High Ba and ³⁴S-enriched barite document internal Ba recycling in a paleo-SMTZ. Enhanced Hirnantian–Rhuddanian productivity and anoxia, followed by more oxygenated Aeronian conditions and greater carbonate–clay input, together with sustained OSR and SD-AOM, controlled concretion nucleation and cementation. Overall, these concretions offer a useful record of how ancient marine environments, carbon cycling and early burial processes interacted in organic-rich sediments.</div></div>","PeriodicalId":100819,"journal":{"name":"Journal of Palaeogeography","volume":"15 5","pages":"Article 100393"},"PeriodicalIF":2.0,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148935316","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Zircon petrochronology of Upper Devonian–Lower Carboniferous sandstones from Armenia: New insights into the evolution of the northeastern margin of Gondwana","authors":"Cesar Witt,&nbsp;Marc Poujol,&nbsp;Olivier Bruguier,&nbsp;Jorge Iglesias,&nbsp;Massimo Chiaradia,&nbsp;Vahram Serobyan,&nbsp;Catherine Cronier,&nbsp;Arayik Grigoryan,&nbsp;Monique Seyler,&nbsp;Taniel Danelian","doi":"10.1016/j.jop.2026.100415","DOIUrl":"10.1016/j.jop.2026.100415","url":null,"abstract":"<div><div>Zircon petrochronology provides key insights into the sedimentary evolution of ancient terranes. We analyzed ∼470 detrital zircons from two Upper Frasnian–Lower Famennian and one Upper Famennian–Visean sections of the South Armenian Block (SAB) using U–Pb geochronology, Lu–Hf and O isotopes, and trace-element geochemistry. These successions document the final episodes of siliciclastic deposition along northeastern Gondwana. All sandstones are highly quartz-rich (&gt;90%), reflecting long-distance transport. About 350 concordant U–Pb ages define older clusters (∼19%), Neoproterozoic (∼63%), and Paleozoic (18%), with peaks at ∼2.5 Ga, ∼910 Ma, ∼600 Ma, and ∼350 Ma, consistent with eastern Gondwanan provenance. Zircon ϵHf(t) (up to −30) and δ¹⁸O data (up to 12) for the 600–500 Ma and 900–700 Ma groups indicate derivation from highly evolved sources. Trace-element proxies (U/Yb, LREE/HREE, Ce/Y) display bell-shaped distributions peaking at 700–500 Ma, further pointing to a mixture of evolved and mildly juvenile sources. Zircon petrochronological constraints suggest that the main contributors were likely the sedimentary cover of the Arabian–Nubian Shield, supplemented by more distal Pan-African basement domains such as the Saharan Metacraton and Mozambique Belt. A relative scarcity of 600–500 Ma age zircons, together with recycled ϵHf(t) values, indicates only minor input from the Cadomian arc. The increase in zircon ϵHf(t), together with the marked decrease in U/Yb, LREE/HREE, and Ce/Y after 500 Ma, indicates a shift toward more oceanic-like geochemical signatures, reflecting attenuation of the continental contribution during the early rifting of northern Gondwana terranes. Taken together, the high maturity, peripheral Gondwanan setting, stratigraphic facies, age spectra, and isotopic signatures of the SAB sandstones support their interpretation as very distal representatives of the eastern Gondwana super-fan system.</div></div>","PeriodicalId":100819,"journal":{"name":"Journal of Palaeogeography","volume":"15 5","pages":"Article 100415"},"PeriodicalIF":2.0,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148935318","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ichnological analysis of the Paleocene–Eocene Thermal Maximum along a continental–marine transect reveals a protracted recovery at deep marine settings","authors":"Olmo Miguez-Salas,&nbsp;Luis Valero,&nbsp;Francisco J. Rodríguez-Tovar","doi":"10.1016/j.jop.2026.100414","DOIUrl":"10.1016/j.jop.2026.100414","url":null,"abstract":"<div><div>During the Paleocene–Eocene Thermal Maximum (PETM), global temperatures rose, negative carbon isotope excursion (CIE) occurred and widespread oceanic deoxygenation happened, leading to biotic turnover. Moreover, a Pre-Onset Excursion (POE) has been documented globally and claimed to be more similar to ongoing anthropogenic emissions. Understanding how these two events have affected the macrobenthic tracemaker community (e.g., polychaetes, crustaceans, echinodermata, mollusks) provides crucial information for modern and past marine benthic ecology. Here we present an ichnological analysis of both events along a continental–marine transect. The POE had a variable impact at coastal environments while a decrease in trace fossil abundance is observed at platform environments. The PETM onset marked the macrobenthic tracemaker community extinction. However, during the PETM core, abundant root trace fossil beds appeared at coastal areas, probably associated with accelerated hydrological cycles. Then, on the platform, before the CIE recovery starts, the trace fossil assemblage is reestablished, while in the deep-sea, even after the excursion is over, trace fossil abundance only partially recovers. Our study unveils a protracted recovery of the PETM, suggesting that the macrobenthic tracemaker community was under stress for a much longer period in the deep-sea environments of the Pyrenean Basin. Finally, our results indicate that the PETM had a more dramatic impact on the tracemaker community than the POE.</div></div>","PeriodicalId":100819,"journal":{"name":"Journal of Palaeogeography","volume":"15 5","pages":"Article 100414"},"PeriodicalIF":2.0,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148935375","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A tale of seismic and aseismic effects from marine to coastal sedimentation: Study from Proterozoic Vindhyan succession, India","authors":"Sabyasachi Mandal,&nbsp;Kaustav Das,&nbsp;Pronobesh Roy","doi":"10.1016/j.jop.2026.100392","DOIUrl":"10.1016/j.jop.2026.100392","url":null,"abstract":"<div><div>Syn-sedimentary liquefaction-fluidization-induced soft-sediment deformation structures (SSDS) triggered by both seismic and aseismic processes, are commonly used to infer ancient hydrodynamics condition and tectonics; however our compressive understanding of seismic and aseismic processes in sedimentation remains limited. The study explores several SSDS beds preserved in the multiple stratigraphic intervals of 1.75 Ga to 0.75 Ga Vindhyan sediment succession, India. Sedimentological study conveys that the studied carbonate to siliciclastic sediment has deposited in marine shelf to lagoon, with an exception of aeolian environment. The laterally continuous-extensive, recurrent SSDS preserved in carbonate succession of 1.6 Ga and 0.9 Ga infer that SSDS are possibly seismites. The change of depositional dynamics from lagoon to open marine at onset of seismites confirm the seismicity origin. The shallow marine shelf siliciclastic and lagoonal carbonate succession records multiple SSDS as topmost deposition of meter-scale coarsening up sequence. Thess SSDS are interpreted as the imprint of repetitive basin subsidence, followed by sedimentation that was subsequently influenced by intrabasinal rift tectonics. The open marine carbonate shelf preserving meter-scale fining-up cycle with SSDS at base is the record of tempestite. The tidal shelf records include overturned cross-bedding and convolute laminations which are the prominent features of tidalites. Tsunami waves ingress into the costal dune field imprint producing convolute lamination, and thick muddy sediment decode as the tsunamites. This study infers that seismicity and tsunami can modify depositional regime, whereas storm, tides, intrabasinal rift tectonics continue to sustain similar sedimentation. The origin of the earthquakes may be linked to the assembly and drift of the northern and southern Indian block as well as to the interplay between tectonics and sedimentation in the Vindhyan Basin. However detailed constraints on the depostitional ages and tectonic evolution remain a key objective for future study.</div></div>","PeriodicalId":100819,"journal":{"name":"Journal of Palaeogeography","volume":"15 5","pages":"Article 100392"},"PeriodicalIF":2.0,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148935317","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hydrocarbon reservoirs in glaciogenic sediments? – The late Ordovician (Hirnantian) succession of North Africa and the Arabian Peninsula","authors":"Mats O. Molén","doi":"10.1016/j.jop.2026.100382","DOIUrl":"10.1016/j.jop.2026.100382","url":null,"abstract":"<div><div>Since the middle of the 20th century, the origin of the Hirnantian deposits of North Africa and the Arabian Peninsula have been interpreted as evidence of large-scale glaciation. In spite of this long held interpretation, a summary of documented data from this area indicates no evidence of full scale glaciation, but rather a more spasmodic or catastrophic origin of the geologic features, possible with outflow of subsurface water similar to what has been interpreted at our neighbour planet Mars. The evidence is of massive flows of water and sediment gravity flows (SGFs) connected to tectonics. The origin and transport of hydrocarbons in the area may be spasmodic, and there is no evidence of connection to continental-wide glaciation. A Diamict origin table is used to sum up the evidence of geologic features which have been interpreted to be from glaciation, and if these are better explained by glaciation or other geological processes.</div></div>","PeriodicalId":100819,"journal":{"name":"Journal of Palaeogeography","volume":"15 4","pages":"Article 100382"},"PeriodicalIF":2.0,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148553956","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Neoproterozoic rocks of the Garvellachs, Scotland","authors":"David J. Tyler","doi":"10.1016/j.jop.2026.100386","DOIUrl":"10.1016/j.jop.2026.100386","url":null,"abstract":"<div><div>Glacial features in basement rocks were first interpreted in 1871, located on the Scottish island of Islay. It was a century later that a detailed memoir of the glacial geology of Islay and the Garvellachs was published, which remains an essential source to this day. The Garvellachs are islands to the north–east of Islay, and they provide a showcase for what became known as the Port Askaig Formation. These particular rocks are of Neoproterozoic age and have been used to correlate diamictite-like sediments from localities ranging from Connemara in Ireland to the north–east of Scotland. Different views, however, have emerged about the interpretation of depositional environments.</div><div>This work has three aims: to review geological evidences and disputed interpretations; to highlight issues deserving greater attention; and to re-appraise the significance of the geology of the Garvellachs.</div><div>There are three main models of diamictite formation, each reflecting different depositional processes: (1) movement of grounded ice, which physically transports and deposits unsorted material; (2) glacial rainout, where debris is released from melting ice into water; and (3) mass-flow deposits, resulting from gravity-driven sediment flows that may occur independently of glacial influence. Published discussions of these models are summarised to show that the evidence has ambiguities.</div><div>This paper contributes to the discussion by focusing on four broader contextual issues. First, the global tectonic framework indicates that tectonics not only accounts for basinal subsidence exceeding 1000 m, but also actively drives processes of erosion and sediment deposition. Second, this dynamic tectonic regime can generate a wide range of sedimentary features, including those characteristic of diamictites. Third, the quartz-rich sandstones deserve a status greater than interbeds signalling interglacial phases, and they point to an active depositional system driven by tectonics. Fourth, the presence of dolostones poses a challenge for proponents of glaciation. Evidence suggests that freshly precipitated dolomite formed substantial layers of relatively pure sediment. Traditionally, dolomite is associated with warm, tropical waters, yet the Garvellachs’ dolostones represent a prominent component of the succession. The reappraisal presented here is that the Garvellachs are a witness to active tectonism in Neoproterozoic times, not glaciation.</div></div>","PeriodicalId":100819,"journal":{"name":"Journal of Palaeogeography","volume":"15 4","pages":"Article 100386"},"PeriodicalIF":2.0,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148553958","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unexpected diversity of Orbiculoidea in the northern Paraná Basin: Insights into Devonian faunal dynamics in Gondwana","authors":"Victor Rodrigues Ribeiro,&nbsp;Luiz Felipe Aquino Corrêa,&nbsp;Felipe Nascimento Sousa,&nbsp;Silane Aparecida Ferreira da Silva Caminha,&nbsp;Renato Pirani Ghilardi","doi":"10.1016/j.jop.2026.100374","DOIUrl":"10.1016/j.jop.2026.100374","url":null,"abstract":"<div><div>Recent fossil finds in the northern Paraná Basin (Brazil) allow us to reconsider the paleobiogeographic configuration of the Devonian (Pragian–Emsian) of southwestern Gondwana. Expanded distribution of <em>Orbiculoidea xinguensis</em>, associated with two new species <em>O. matogrossensis</em> sp. nov. and <em>O. triangularis</em> sp. nov., reveal a previously underestimated diversity in this basin. Morphometric analyses and comparative taxonomy were used to differentiate species within the <em>Orbiculoidea</em> genus, highlighting diagnostic features, including apex positioning, valve contour, and rugella patterns. <em>O. triangularis</em> sp. nov. presents distinct morphospaces from <em>O. matogrossensis</em> sp. nov. and <em>O. xinguensis</em>, possibly due to environmental stresses associated with transgression. The presence of <em>O. xinguensis</em>, originally restricted to the Lochkovian of the Amazon Basin, suggests initial marine connectivity between these regions during the Pragian–Emsian, facilitated by transgressive pulses that enabled faunal exchange. The co-occurrence of cosmopolitan (<em>O. baini</em> and <em>O. excentrica</em>) and endemic taxa denote a regime of moderate provincialism, with niche partitioning and speciation. The peak of diversity of the genus during the Pragian–Emsian is followed by a sharp decline in the Eifelian–Givetian in South America, and is directly correlated with transgressive events and habitat fragmentation during the Kačák Event, triggering the Lilliput effect in <em>O. baini</em> and <em>O. excentrica</em>. While marginal intracratonic basins faced local extinctions, they acted as refugia (<em>e.g.</em>, the Bokkeveld Formation of South Africa). The Paraná Basin was an active center of speciation for <em>Orbiculoidea</em>, promoting faunal exchange and biogeographic connectivity of Gondwana during the Devonian.</div></div>","PeriodicalId":100819,"journal":{"name":"Journal of Palaeogeography","volume":"15 4","pages":"Article 100374"},"PeriodicalIF":2.0,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148553955","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Early Cambrian (Age 3) archaeocyath-built reefs developed in the Hannan–Micangshan area, South China: Sedimentary features and ecological significance","authors":"Ya-Lan Li,&nbsp;Fei Li,&nbsp;Xia Wang,&nbsp;Ben Yang,&nbsp;Lei Zhang,&nbsp;Zeng-Jun Wang,&nbsp;Yang-Fan Li,&nbsp;Ying Li,&nbsp;Lu Shi,&nbsp;Chuang Zhong","doi":"10.1016/j.jop.2026.100390","DOIUrl":"10.1016/j.jop.2026.100390","url":null,"abstract":"<div><div>Early metazoan reefs provide important insights into the early development of complex marine ecosystems and life–environment co-evolution. Here we present a sedimentological investigation of the upper Xiannüdong Formation (Cambrian Stage 3) at the Xiaoshenshan section in the Hannan–Micangshan area of South China. A total of eight lithofacies and two archaeocyath-built reef types have been recognized, the latter of which were previously undocumented from South China. The first type comprises small lenticular buildups (typically 20–30 cm thick and 20–40 cm long) formed at or slightly below the fair-weather wave base (mid-ramp setting). These buildups nucleated on stacked, platelike archaeocyath skeletons and developed a dense composite framework of archaeocyaths and calcimicrobes, with shelter cavities hosting cryptic communities and associated dwellers (e.g., trilobites, echinoderms, and small shelly fossils). The second type is a shallow-water, low-relief buildup (∼60 cm high and &gt;3 m wide) formed in a moderate-energy distal inner ramp setting. Nucleated on stabilized ooid sand substrates and hosting a dweller assemblage compositionally comparable to but less abundant than that of the lenticular reefs, this reef exhibits morphological and architectural variability that likely reflects contrasting paleoenvironmental conditions and divergent ecological strategies. Together with known calcimicrobe-dominated buildups, these findings reveal greater-than-previously-recognized diversity in early Cambrian reef architecture in South China, and constrain the ecological differentiation and environmental controls that governed early metazoan reef development.</div></div>","PeriodicalId":100819,"journal":{"name":"Journal of Palaeogeography","volume":"15 4","pages":"Article 100390"},"PeriodicalIF":2.0,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148553960","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Genesis of travertine associated with mafic–intermediate volcanic source rocks: Sedimentological and geochemical insights from Xiabiaoyuan, Tengchong, SW China","authors":"Zhi-Peng Lu,&nbsp;Lian-Chao Luo,&nbsp;Hua-Guo Wen,&nbsp;Enrico Capezzuoli,&nbsp;Liang Li,&nbsp;Ya-Xian You,&nbsp;Ya-Xin Xu,&nbsp;Hui-Xuan Huang,&nbsp;Lei Du","doi":"10.1016/j.jop.2026.100391","DOIUrl":"10.1016/j.jop.2026.100391","url":null,"abstract":"<div><div>Travertine has been found to originate from various source rocks, especially carbonates and granitoids, but little is known about those derived from mafic or intermediate volcanic rocks. Therefore, detailed hydrochemical, sedimentological, and isotopic characteristics of the Xiabiaoyuan travertine system (Tengchong, SW China), which developed on Quaternary olivine trachybasalt and basaltic trachyandesite substrata, were investigated here. The travertine build-up is confined within an area approximately fifty-five meters wide and thirty-five meters long, with a height of about seven meters. The spring water is of meteoric origin and exhibits a relatively low water temperature (between 23.6 °C and 29.5 °C) and exceptionally high [Mg²⁺]/[Ca²⁺] (varying from 16.6 to 46.3) ratio, which is attributed to olivine-rich aquifer rocks. Four depositional environments were identified from the vent to the distal area (vent pool, discharge pool, gentle smooth slope, and terraced slope), with travertine deposition occurring in the latter three. The travertine was composed entirely of aragonite and five lithotypes were identified, including reed travertine, crystalline crust, paper-thin raft travertine, coated bubble travertine, and filamentous boundstone. Changes in depositional environments led to the formation of these diverse lithofacies. Travertine formation is primarily driven by CO₂ degassing, while the exclusive presence of aragonite is attributed to the high [Mg²⁺]/[Ca²⁺]. Our isotopic analyses indicate 1) a thermogene origin of the travertine, with parent CO₂ mainly of magmatic origin, and 2) a mixed Sr origin from mafic–intermediate volcanic rocks and their underlying Cretaceous–Paleogene granitoids. Based on these, a formation model, from subsurface fluid circulation to surface travertine deposition, was constructed. Overall, this study suggests that mafic–intermediate volcanic source rocks strongly influenced the characteristics of travertine, particularly in terms of its mineralogical and ⁸⁷Sr/⁸⁶Sr characteristics. This first comprehensive sedimentological and isotopic study of travertine linked to mafic–intermediate volcanic source rocks may offer new insights into travertine genesis in similar settings and into the reconstruction of (paleo-)hydrogeological aquifer lithology in (paleo-)spring systems.</div></div>","PeriodicalId":100819,"journal":{"name":"Journal of Palaeogeography","volume":"15 4","pages":"Article 100391"},"PeriodicalIF":2.0,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148634267","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sedimentary environment and organic matter enrichment mechanisms of Lower Cretaceous source rocks in the Hari Sag, Yingen-Ejinaqi Basin","authors":"Zhi-Jun Chen,&nbsp;Ya-Xiong Zhang,&nbsp;Deng-Feng Wei,&nbsp;Yong-Hong He,&nbsp;Xiao-Yin Bai,&nbsp;Yi-Guo Chen","doi":"10.1016/j.jop.2026.100372","DOIUrl":"10.1016/j.jop.2026.100372","url":null,"abstract":"<div><div>In this study, we examined the Hari Sag in the Yingen-Ejinaqi Basin as a case study to investigate the factors controlling organic matter (OM) enrichment and the related mechanisms in small- to medium-sized faulted lake basins in northern China. Based on TOC and elemental geochemistry data from mudstone samples, we reconstructed the sedimentary environment and its evolution of the study area during the Early Cretaceous. We further investigated the mechanisms of OM enrichment in the source rocks and developed a corresponding enrichment model. The results reveal the sedimentary environment and evolutionary characteristics of the Early Cretaceous in the study area. Paleoclimate of the study area shifted from semi-humid to arid, and finally to semi-humid. Meanwhile, the redox conditions of the water column evolved from oxidizing to weakly oxidizing (or weakly reducing), then returned to oxidizing, and finally shifted to weakly oxidizing (or weakly reducing). Paleosalinity increased overall from fresh water to saline water conditions. Specifically the paleowater depth was relatively deep during the deposition of the first and second members of the Bayingobi Formation (K₁b¹ and K₁b²), relatively shallow during the deposition of the third member of the Bayingobi Formation (K₁b³) and the Suhongtu Formation (K₁s), and reached its maximum during the deposition of the Yingen Formation (K₁y). Synsedimentary hydrothermal activity was common during the Early Cretaceous in the study area, with varying intensities among different stratigraphic intervals. Changes in regional tectonic and climatic environments jointly influenced the paleosalinity and the paleowater depth, and other factors, determining the lake paleoproductivity of each stratigraphic interval in the study area. Redox conditions and paleosalinity influenced OM preservation, thereby determining the degree of OM enrichment in each interval. Synsedimentary hydrothermal activity also enhanced OM enrichment to a certain extent, and variations in hydrothermal intensity across different sedimentary periods led to differences in OM enrichment. Based on this, we further established an OM enrichment model for small- to medium-sized faulted lake basins dominated by tectonic movement, paleoclimate, and hydrothermal sedimentation. Our findings provide a reference for similar studies and offer a basis for source rock prediction in analogous small- to medium-sized faulted lake basins.</div></div>","PeriodicalId":100819,"journal":{"name":"Journal of Palaeogeography","volume":"15 4","pages":"Article 100372"},"PeriodicalIF":2.0,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148553957","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}