Sedimentary Geology最新文献

{"title":"Unravelling organic rich shale formation using geochemical proxies in the Doushantuo Formation, South China","authors":"Junfeng Zhang ,&nbsp;Detian Yan ,&nbsp;Zeyu Lu","doi":"10.1016/j.sedgeo.2026.107042","DOIUrl":"10.1016/j.sedgeo.2026.107042","url":null,"abstract":"<div><div>The black shale of the Doushantuo Formation provides important insights into the Ediacaran geological environment and organic carbon enrichment with shale gas potential and exploration. As a typical marine shale with high organic carbon content and considerable thickness, it also holds significant resource potential. In this study, shale samples from multiple water depths and depositional environments across the middle Yangtze block, were examined by well log analysis, field surveys, and lithological divisions. We identified four distinct systems tracts within the second member of Doushantuo Formation (DST-2). High-resolution total organic carbon (TOC) profiles recorded several discrete enrichment pulses. These pulses vary systematically across systems tracts and water depths. This pattern suggests changes in organic-matter supply and preservation and these changes are driven by shifts in water-column redox structure. They are also linked to episodic upwelling. Together, these factors control organic carbon accumulation. Enrichment occurred primarily during transgressive phases, driven by varying water column redox conditions and persistent upwelling. Notably, deeper-water shales showed stronger organic matter enrichment than shallow-water shales did, highlighting the importance of deep-water environments for shale gas exploration. By integrating a sequence-stratigraphic framework with high-resolution TOC data across a nearshore–offshore transect, we constrain the timing and controls of episodic organic carbon enrichment in DST-2. The results highlight transgressive-phase enrichment driven by redox stratification and persistent upwelling; and demonstrate that deep-water settings consistently hosted higher TOC and thicker organic-rich intervals, thereby refining most prospective facies and intervals for shale-gas exploration.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"494 ","pages":"Article 107042"},"PeriodicalIF":2.9,"publicationDate":"2026-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146079586","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":"Polymetallic nodules offshore NE Greenland: links to Fram Strait opening and local hydrothermal activity","authors":"Dmitrii Zastrozhnov ,&nbsp;John M. Millett ,&nbsp;Sverre Planke ,&nbsp;Stéphane Polteau ,&nbsp;Adriano Mazzini ,&nbsp;Derek Fabel ,&nbsp;Finlay Stuart ,&nbsp;Ana Carracedo ,&nbsp;Luigia Di Nicola ,&nbsp;Valerie Olive ,&nbsp;Nina Lebedeva-Ivanova ,&nbsp;Iakov Gogin ,&nbsp;Reidun Myklebust ,&nbsp;Ebbe H. Hartz","doi":"10.1016/j.sedgeo.2026.107033","DOIUrl":"10.1016/j.sedgeo.2026.107033","url":null,"abstract":"<div><div>This study presents the first documentation and analysis of polymetallic Fe–Mn seafloor nodules from offshore Northeast Greenland. Samples were collected from three sites by dredging and gravity coring along the slopes of both the outer and transform margin highs. The morphology, petrography, and whole-rock geochemistry of twenty-four nodules were determined. ¹⁰Be/⁹Be and (U–Th)/He dating were undertaken for representative samples to constrain the time of formation. Two nodule groups were identified in all studied sampling sites. Group 1 (<em>n</em> = 19) are light banded, primarily hydrogenetic nodules with notable enrichments in Mn and Fe, as well as several trace elements including rare earth elements (REE), V, Co, and Y. They have geochemical and textural similarities to Fe–Mn deposits from the Arctic Basin. ¹⁰Be/⁹Be age estimates suggest that growth initiated around 13,5 Ma, shortly after the opening of the Fram Strait, which influence deep-water circulation and inflow of nutrient-rich Arctic waters onto the NE Greenland shelf. Group 2 nodules (<em>n</em> = 5) are dense with high Fe (up to 64 wt% Fe₂O₃), low Mn content and little to no enrichment in trace elements and REEs. They are interpreted as hydrothermal in origin, with preliminary (U–Th)/He ages suggesting Quaternary formation under weak, diffuse fluid circulation in near-bottom environments of uncertain source. This study expands our understanding of seafloor mineralization in the Arctic–North Atlantic gateway, revealing that on the NE Greenland shelf this process reflects a long-term interplay between tectonic evolution, ocean circulation, and fluid-driven alteration.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"495 ","pages":"Article 107033"},"PeriodicalIF":2.9,"publicationDate":"2026-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146116410","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":"Mud volcanoes and synsedimentary deformation structures in Miocene lacustrine deposits over evaporites: Evidence of seismite interpretation","authors":"M.E. Sanz-Montero ,&nbsp;C. Giraldo ,&nbsp;J.P. Rodríguez-Aranda","doi":"10.1016/j.sedgeo.2026.107043","DOIUrl":"10.1016/j.sedgeo.2026.107043","url":null,"abstract":"<div><div>In continental tectonic basins, evaporite paleokarst and soft sediment deformation structures can occur together. However, distinguishing between the effects of tectonism and karst-related dissolution is challenging. Highly deformed beds overlying an evaporite paleokarst in the Miocene deposits of Madrid Basin have been studied in exceptional and laterally continuous outcrops. The paleokarst overburden is mudstone-dominated and displays closely packed fluid seepage structures in the form of mud breccias, tubes, fractures and veins networks connected to surface. At fault intersections, these features dip inwards decametric bowl-shaped to funnel-like structures bounded by circular fractures. This supports that these depressions represent collapsed mud volcanoes built at the surface by the fluid seepage features. They developed in periods of high pore pressures favoured by compressional regimes. Associated fluidization structures including in situ breccia, plastic intrusions, convolute and load forms support that earthquakes are the triggering mechanism.</div><div>The network of conduits is lithified by carbonate cements, including slickenfibers of aragonite, as well as by oxides of rare earths and iron‑manganese. The calcite and aragonite cements are highly depleted in ¹⁸O in comparison with the hosts suggesting overpressured aquifers as the source of freshwater fluids.</div><div>This analogue provides clues to identifying ancient, sagged beds as evolved fluid seepage systems and help to recognizing seismic events in lacustrine environments. Interpretations of sagging structures, common in worldwide-evaporitic paleokarst as purely dissolution-driven should be revisited considering the potential tectonic controls behind their rapid and extensive formation.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"494 ","pages":"Article 107043"},"PeriodicalIF":2.9,"publicationDate":"2026-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146079589","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":"Sedimentary evolution under high-frequency sea-level oscillations of the lower Triassic carbonate-evaporite system in Xuanhan area, Sichuan Basin: Implications for the genesis of polyhalite minerals","authors":"Fanfan Zuo ,&nbsp;Yongsheng Zhang ,&nbsp;Baoling Gui ,&nbsp;Kui Su ,&nbsp;Enyuan Xing ,&nbsp;Xinsheng Niu ,&nbsp;Yuan Peng ,&nbsp;Yan Xue","doi":"10.1016/j.sedgeo.2026.107032","DOIUrl":"10.1016/j.sedgeo.2026.107032","url":null,"abstract":"<div><div>Polyhalite is a common potassium-bearing mineral of many ancient evaporitic systems, which can provide important ore resources for agricultural development. However, the genesis of polyhalite is still debated, especially for the origin of primary type. In order to provide novel perspectives and evidence for the genesis of polyhalite minerals, detailed sedimentological and sequence stratigraphic analyses, combined with sulfur isotope stratigraphy, were carried out using Lower Triassic core data in the Xuanhan area, northeastern Sichuan Basin. Fifteen microfacies grouped into six microfacies associations were identified. Furthermore, facies cycle types were recognized and the target intervals were subdivided into six fourth-order sequences and multiple parasequences within them. The result of fourth-order sequences was further validated by sulfur isotope chemostratigraphy. Sedimentary models in the study area and a formation model for primary polyhalite were established consequently. The coupled effects of paleoenvironmental conditions, tectonic activities, and provenance supply caused by sea-level fluctuations collectively led to the precipitation of primary polyhalite in the Sichuan Basin during the Early Triassic. Specifically, primary polyhalite occurs when K⁺- and Mg²⁺-enriched concentrated brine within halite saltern mixes with external influxes carrying Ca²⁺ and SO₄²⁻ ions, a process regulated by the dynamic fluctuations of multi-order sea-levels, especially the high-frequency ones. Moreover, the margins of the halite saltern and the gypsum saltern, as well as the spatial transition zone between them, created an ideal setting that can meet the above-mentioned geochemical conditions for the precipitation of polyhalite. These results contribute to the supplementation and refinement of the formation mechanisms of polyhalite minerals, especially for the primary ones.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"494 ","pages":"Article 107032"},"PeriodicalIF":2.9,"publicationDate":"2026-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146079588","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":"Sedimentology and sequence architecture of the inner shelf siliciclastic‑carbonate succession of the Lower to Middle Jurassic Shusha Formation, Gebel El-Maghara, North Sinai, Egypt","authors":"Mounir H. El-Azabi","doi":"10.1016/j.sedgeo.2026.107031","DOIUrl":"10.1016/j.sedgeo.2026.107031","url":null,"abstract":"<div><div>The sedimentological characteristics of Lower to Middle Jurassic deposits are poorly defined in the southern Tethys. These deposits represent shallow marine siliciclastic‑carbonate facies in Gebel El-Maghara, North Sinai, marked by vertically stacked meter-scale cycles; their origin remains unclear. They include a well-preserved example of Aalenian sediments, which are not so ubiquitous around the Tethys. An integrative sedimentological and sequence stratigraphic study provides new insights into the sedimentation patterns and stratal architecture of the siliciclastic‑carbonate cycles, representing the first cyclostratigraphic research on Uppermost Toarcian–Lower Bajocian deposits in the southern Tethys. The siliciclastic facies include shale and sandstone of barrier-island/lagoon, estuary, and beach-ridge strandplain, developed along a northwestward-dipping coast on an inner shelf during transgressive and early regressive events. The carbonate facies comprise limestone and dolostone, which formed during falling sea levels, marking late regressive events. Facies characteristics indicate the development of a passive-margin shelf in North Sinai during the latest Early Jurassic, earlier than previously assumed. The transgressive-regressive cycles reflect reciprocal sedimentation of alternating siliciclastic and carbonate systems, a relatively uncommon pattern in the geologic record. At intervals, deep incisions, along with dolomitization and ferribands, interrupt these cycles, leading to the formation of incised valleys filled with fluvial sandstones and estuarine sands deposited during sea-level rise. The incised valleys and other discontinuities divide the transgressive-regressive cycles into five distinct depositional sequences, each separated by boundaries linked to short-term eustatic sea-level falls. These falls, combined with a humid climate, largely controlled the initiation of incised valleys, resulting in sequence incompleteness, variations in cycle numbers and durations within equivalent sequences, and the preservation of lowstand deposits along the inner shelf. The clear record of global eustatic sea-level changes preserved on the passive-margin shelf enables more accurate dating of these sequences, revealing that the enclosed low-amplitude, high-frequency cycles have average durations of 54–400 kyr. These fourth- to fifth-order cycles were likely driven by climatic variations within the Milankovitch frequency band and are probably linked to global cooling intervals during the Aalenian and Bajocian.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"494 ","pages":"Article 107031"},"PeriodicalIF":2.9,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146079587","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":"Multi-phase tectonic evolution regulating multi-source provenance and spatio-temporal sedimentary migration in the Middle-Upper Ordovician, Tarim Basin (NW China)","authors":"Qian Liu ,&nbsp;Jun Wu ,&nbsp;Tailiang Fan ,&nbsp;Pengfei Wu ,&nbsp;Weiguo Zhang ,&nbsp;Suju Yang ,&nbsp;Qinqi Xu ,&nbsp;Yongtao Xia ,&nbsp;Mingjie Lan","doi":"10.1016/j.sedgeo.2026.107030","DOIUrl":"10.1016/j.sedgeo.2026.107030","url":null,"abstract":"<div><div>The Middle-Upper Ordovician succession in the Tarim Basin documents the evolution of a “reactivated cratonic basin” during the transition from a passive to a collisional continental margin. Deep exploration is hindered by extreme burial depths, limited seismic resolution, and unclear tectonic-sedimentary coupling mechanisms. This study integrates outcrops, cores, well logs, seismic data, and geochemical analyses to establish a high-resolution sequence stratigraphic framework, reconstruct the provenance evolution history, and decipher the spatio-temporal migration of sedimentary systems. Five third-order sequences (SQ1–SQ5) were identified: SQ1—upper Yijianfang and Qiaerbake Formations; SQ2—Lianglitage and lower Sangtamu Formations; SQ3–SQ5—middle–upper Sangtamu Formation. Provenance evolution exhibits a clear tectonically controlled three-stage pattern: during SQ1–SQ2, extra-basinal sources dominated, primarily from the Altyn Orogenic Belt, driven by its east-west “scissor-like” oblique collision; SQ3 was a mixed-source stage with contributions from both the Altyn Orogenic Belt and the Tazhong and Tabei paleo-uplifts, responding to intensified arc-continent collision and intra-basinal tectonic activation; SQ4–SQ5 transitioned to intra-basinal source dominance. The evolution of sedimentary systems was jointly controlled by the coupling of extra-basinal and intra-basinal tectonic dynamics, tectonically driven provenance migration, and relative sea-level fluctuations, overall showing a transition from deep-water gravity flow systems to shallow-water deltaic systems: (1) SQ1–SQ2 featured eastern submarine fans and western carbonate platforms; (2) SQ3 saw expanded eastern submarine fans and newly developed western slope turbidite fans; (3) SQ4–SQ5 were dominated by a basin-center “shelf to shelf-edge delta” system, with gradual shrinkage of the eastern deep-water fans. This study clarifies the core coupling mechanism of “tectonic activation driving provenance transformation, which in turn controls sequence distribution and sedimentary migration,” and establishes a “reactivated cratonic basin” sedimentary evolution model applicable to the Tarim type. The research results provide an important reference for the tectonic-sedimentary analysis of intracratonic collisional basins globally.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"493 ","pages":"Article 107030"},"PeriodicalIF":2.9,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145981697","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":"Influence of geomorphological dynamics and associated mineralogical structures on carbon mineralization processes within different surfaces of sand ramps","authors":"Mohsen Kargarian,&nbsp;Neda Mohseni,&nbsp;Reza Hosseinzadeh","doi":"10.1016/j.sedgeo.2026.107029","DOIUrl":"10.1016/j.sedgeo.2026.107029","url":null,"abstract":"<div><div>Sand ramps are recognized as critical archives for reconstructing Late Quaternary environmental changes, including sediment supply, paleoclimate, and soil carbon dynamics. We investigated the influence of geomorphic processes, weathering, and mineralogical dynamics on the mechanisms controlling the sequestration and mineralization of soil organic carbon (SOC) within falling and climbing sand ramps. Analyses including XRD, XRF, SEM, granulometry, physicochemical attributes, and weathering indices were conducted on sand ramps in central Iran. The abundance of carbonate minerals, sand-sized sediments, well-sorted clastic aggregates, and symmetrical grain distribution, combined with high roundness and minimal quartz corrosion, suggests that falling surfaces remain relatively intact with limited evidence of weathering. Despite the presence of carbonate minerals on falling sand ramps, the lower proportion of clay minerals and fine particles resulted in weaker organic matter binding compared to climbing surfaces. Conversely, the higher frequency of secondary clay minerals, poor sediment sorting, high angularity, and the formation of micro-scale features on granites indicate long-term exposure of climbing surfaces to chemical weathering. The elevated presence of illite, kaolinite, montmorillonite, as well as Fe₂O₃ and Al₂O₃ oxides, supported pedogenic processes and promoted microaggregate-associated carbon, rendering SOC less accessible to microbial mineralization. The findings indicate that climbing sand ramps represent a stabilized, pedogenically altered colluvial-aeolian apron overlying the granite, where primary sedimentary structures have been obscured by chemical weathering and clay illuviation. This contrasts with the structurally intact, gravity-dominated falling ramps. These results suggest that localized variations in geomorphic and weathering processes, alongside mineralogical composition, significantly influence the biogeochemical mechanisms controlling SOC mineralization throughout the evolution of sand ramps, offering valuable insights into carbon dynamics in arid and semi-arid regions.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"494 ","pages":"Article 107029"},"PeriodicalIF":2.9,"publicationDate":"2026-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145982104","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":"A novel mechanism of uranium mineralization: The role of zircon adsorption at the Qigequan deposit, Qaidam Basin, NW China","authors":"Yi-Han Lin ,&nbsp;Ming-Sen Fan ,&nbsp;Pei Ni ,&nbsp;Jun-Yi Pan ,&nbsp;Zhe Chi ,&nbsp;Zhi-Lin Cheng ,&nbsp;Wen-Yi Wu ,&nbsp;Chen Zhang ,&nbsp;Bing-De Qi ,&nbsp;Xue-Bin Wei","doi":"10.1016/j.sedgeo.2026.107027","DOIUrl":"10.1016/j.sedgeo.2026.107027","url":null,"abstract":"<div><div>Uranium mineralization in sandstone-hosted deposits is influenced by the adsorption capacity of minerals, especially in basin fluids with sub-saturation uranium concentrations. This study investigates the Qigequan sandstone-type uranium deposit in the Qaidam Basin, focusing on uranium distribution and adsorption behavior in zircon. Samples were analyzed using TIMA, BSE, CL imaging, EDS, and EPMA. Results show zircon is abundant in both matrix and clastic components, with uranium occurring in three forms: U1 (in growth zones or inclusions), U2 (in fractures), and U3 (on grain rims). U1 is a magmatic or early hydrothermal product with low U/Th, while U2 and U3 are associated with surface adsorption by mineralizing fluids and have high U/Th. By contrast, uranium minerals unrelated to zircon (i.e., Other-U) have different Th and U characteristics. EPMA mapping reveals that absorbed uranium around rims correlates with elements like Th, Y, Mg, and Ti. Zircon demonstrates a stronger and more selective uranium adsorption capacity than other accessory minerals, despite their higher abundance. We suggest that uranium is absorbed by zircon through a physical-chemical adsorption mechanism, primarily controlled by pH changes caused by the mixing of mildly alkaline oil-gas-related fluids and supergene oxidized fluids. These findings highlight the significant role of zircon as a uranium adsorbent in sandstone-hosted uranium deposits and suggest that surface adsorption, in addition to classical precipitation due to fluid supersaturation, is an important pathway for uranium enrichment. This mechanism offers new insights into uranium mineralization and may refine genetic models of sandstone-type uranium deposits.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"493 ","pages":"Article 107027"},"PeriodicalIF":2.9,"publicationDate":"2026-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145950266","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":"A best-practices guide to X-ray diffraction studies of sedimentary carbonates","authors":"Georgina Lukoczki ,&nbsp;David L. Bish ,&nbsp;Jay M. Gregg","doi":"10.1016/j.sedgeo.2026.107028","DOIUrl":"10.1016/j.sedgeo.2026.107028","url":null,"abstract":"<div><div>The accurate identification of sedimentary dolomites and related Ca-Mg carbonates is critical for understanding their formation and, by extension, the evolution of Earth's oceans and climate. However, the literature contains numerous examples of misapplication and misinterpretation of X-ray diffraction (XRD) data. For instance, experimental studies claiming successful low-temperature dolomite synthesis have frequently misidentified very high-Mg calcite (VHMC) or other phases as dolomite due to incorrect evaluation of XRD data. Rigorous analytical standards are needed to avoid misinterpretations and to advance the understanding of sedimentary dolomite formation. This paper provides a best-practices guide for powder XRD analysis of trigonal carbonate minerals, with particular emphasis on Rietveld refinement methods for evaluating cation ordering, unit-cell parameters, crystallite size, strain, and stoichiometry. Recommendations are presented for sample preparation, data collection, and analysis, aimed at improving the reliability of carbonate mineral identification and characterization, with particular emphasis on dolomite. Additionally, the nomenclature and classification challenges in distinguishing calcite, high-Mg calcite, VHMC, protodolomite, dolomite, ferroan dolomite, and ankerite are addressed. Finally, the implications of dolomite mineralogy for interpreting past environmental conditions are critically assessed, highlighting the pervasive effects of recrystallization over geological timescales.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"493 ","pages":"Article 107028"},"PeriodicalIF":2.9,"publicationDate":"2026-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145950267","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":"Steep nested clinoforms in the mixed siliciclastic‐carbonate Eocene Sobrarbe Deltaic Complex, Aínsa Basin, Spain","authors":"Leticia Rodriguez-Blanco ,&nbsp;Miquel Poyatos-Moré ,&nbsp;Ivar Midtkandal ,&nbsp;Ingrid Anell","doi":"10.1016/j.sedgeo.2025.107019","DOIUrl":"10.1016/j.sedgeo.2025.107019","url":null,"abstract":"<div><div>This study investigates and discusses the processes controlling the development of nested clinoforms in outcrops of the Eocene Sobrarbe Deltaic Complex of the Aínsa Basin, and demonstrates that early cementation in fine-grained sediments can help preserving steep deltaic foresets. Small-scale clinoforms (few 10s of m thick, few 100s of m long) record the higher-frequency cycles of delta progradation and the coetaneous development of a carbonate factory, while large-scale clinoforms (several 10s of m thick, few km long) record longer-term high-energy processes on the shelf and slope, including the reworking of previous deltaic/shelf deposits. Detailed lithological analysis across three of the high-frequency cycles reveals a downdip transition along the small-scale clinothems from subaqueous channels to distal delta front and shelf settings. The coarsest grain sizes are restricted to the proximal delta plain deposits evidencing some periods of limited coarse sediment transfer to deeper waters, enabling the development of coeval carbonate production on the delta front/shelf. Early cementation of carbonate-rich horizons preserved the relatively steep, yet fine-grained clinoform slopes and prevented their collapse. Observation of steep cemented foresets in fine-grained lithologies challenges a univocal relation between delta slope and grain size. In addition, we propose that early cementation is linked to in-situ carbonate production, which implies faunal adaptation probably favored by hiatuses in sedimentation between successive stages of delta progradation. The study also emphasizes the importance of recognizing heterogeneity in such mixed siliciclastic‑carbonate environments, and contributes to the understanding of depositional processes and sedimentary architecture in shallow-marine prograding systems.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"493 ","pages":"Article 107019"},"PeriodicalIF":2.9,"publicationDate":"2026-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145981698","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}