Sedimentary Geology最新文献

{"title":"Subglacial conglomerate as a sensitive recorder of the ice-sheet base conditions – An example from eastern Poland","authors":"Barbara Woronko ,&nbsp;Katarzyna Skolasińska ,&nbsp;Małgorzata Pisarska-Jamroży ,&nbsp;Karina Apolinarska ,&nbsp;Joanna Mirosław-Grabowska ,&nbsp;Karolina Ulbin ,&nbsp;Martyna E. Górska","doi":"10.1016/j.sedgeo.2025.106938","DOIUrl":"10.1016/j.sedgeo.2025.106938","url":null,"abstract":"<div><div>This study reports a unique example of an exceptionally compact and hard calcified conglomerate identified in eastern Poland for which we indicate a subglacial formation conditions. To infer its origin, we employed macro- and micro- studies (fieldwork, thin-section analysis), and determined the isotopic composition of the carbonate cements. The conglomerate, ranging in thickness from a few cm up to 70 cm, occurs between the MIS6 age till and underlying glaciofluvial deposits. Its formation is attributed to the advance of an ice sheet over glaciotectonically deformed and permafrost-affected glaciofluvial deposits within a glaciomarginal fan. These frozen deposits formed mega-scale obstacles (folds and rafts) that impeded ice movement, leading to increased subglacial water pressure and the development of a thin water film at the ice-sheet base. The studied conglomerate represents a valuable archive for reconstructing subglacial conditions under active ice sheet, as evidenced by the following features: (1) calcite precipitation on the down-glacial (lee) sides of the ground obstacles; (2) precipitation in phreatic conditions as evidence by continuous cements around mineral grains and the lacking grain-to-grain contact; (3) bipartite structure comprising sparitic and overlaying micritic cement layers; sparite formed under open-drainage subglacial conditions, whereas micritic thin layer developed during the final stage of water film freezing under closed-system; (4) carbon and oxygen isotope compositions confirming the sequential precipitation of sparite followed by micrite. Calcified conglomerates formed during the advance of the ice sheet front onto the substrate covered by permafrost, have not been described in the literature so far.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"486 ","pages":"Article 106938"},"PeriodicalIF":2.9,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144739325","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":"Sea-level controls on terrigenous sediment input to deep water of the Pearl River margin since the last glacial maximum","authors":"Kun Qi ,&nbsp;Chenglin Gong ,&nbsp;Katrine Juul Andresen ,&nbsp;Yang Zhou ,&nbsp;Yibo Geng ,&nbsp;Massine Bouchakour","doi":"10.1016/j.sedgeo.2025.106939","DOIUrl":"10.1016/j.sedgeo.2025.106939","url":null,"abstract":"<div><div>Glacio-eustatic sea-level changes since the Last Glacial Maximum (LGM) have been frequently regarded as the primary driver of terrigenous input to deep-water settings of marginal sea basins. However, on those continental margins where shelf edges lie at water depths farther exceeding 120 m, whether and how eustatic sea-level changes since the LGM have controlled terrigenous sediment input to deep water remains a topic of considerable interest. Taking the Pearl River margin that has a shelf edge with average water depth of 250 m as the study area, we use the depositional records of two piston cores on the head and mouth of a submarine canyon to reconstruct the history of terrigenous input to deep water since the LGM. We then relate the variations of terrigenous input to the contemporary eustatic sea-level changes to examine the details of the role of sea-level changes on terrigenous input. The results indicate that since the LGM there was a three-stage temporal evolution of terrigenous input to deep water on the Pearl River margin. During glacial, deglacial, and interglacial periods, terrigenous input were respectively high, decreasing, and low, correlating well with sea-level lowstands, sea-level rising, and sea-level highstands. Such tight coupling strongly suggests that glacio-eustatic sea-level changes since the LGM could still control terrigenous input to deep water on the Pearl River margin. Specifically, after the LGM, the first rapid sea-level rise, occurred in the periods of Heinrich Stadial 1 (HS1) and Bølling-Allerød (B-A), dramatically inundated the shelf, shifted the shoreline landward and thus, caused a millennial-scale drop of terrigenous input. Within the interglacial period, the sea level had risen almost to its present level and remained relatively stable, during which fluctuations in East Asian Monsoon (EAM) might have an influence on terrigenous input. Therefore, within the interglacial period, terrigenous input, though generally having low levels, showed a slight fluctuation correlated well with the changes of monsoonal climates. This study deepens our knowledge on the fundamental role of sea-level changes in sediment dispersal systems and provides implications for understanding deep-sea dynamics, especially within the context of a continental margin where shelf edges are found at much greater water depths and climatic conditions are rapidly changing.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"486 ","pages":"Article 106939"},"PeriodicalIF":2.9,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144748723","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":"Size does not matter: Glacial record on quartz grains from Pleistocene glacial deposits in Tatra Mts. (Western Carpathians) revealed by scanning electron microscopy","authors":"Dawid Siemek ,&nbsp;Barbara Woronko ,&nbsp;Piotr Kłapyta ,&nbsp;Jerzy Zasadni ,&nbsp;Jacek Szczygieł","doi":"10.1016/j.sedgeo.2025.106937","DOIUrl":"10.1016/j.sedgeo.2025.106937","url":null,"abstract":"<div><div>Microtextures on sand-sized quartz grains can indicate their depositional environments. Glacial tills typically contain grains with abrasion and crushing microtextures, which are considered most intense in subglacial settings. These microtextures were previously thought to vary with ice thickness, transport distance, and basal shear stress. However, the conditions necessary to modify quartz grain morphology in glacial environments remain unclear. In this study, we show that glacier parameters do not directly control quartz grain comminution. We analyzed tills deposited before, during, and after the Last Glacial Maximum (LGM) from five Pleistocene glacial systems in the Tatra Mts. (Western Carpathians), identifying glacially-induced microtextures. The frequency of grains with abrasion and crushing microtextures does not correlate with glacier length (2.3–13.4 km), maximum ice thickness (100–420 m), or basal shear stress (73–151 kPa). We further demonstrate that at least two glacial stages (pre-LGM and LGM) can be distinguished within a single sample based on microtextures preservation (freshness). Additionally, we describe a newly recognized microtexture type: the rosette fracture. Our findings suggest that abrasion and crushing microtextures in warm-based glaciers are primarily influenced by substratum lithology, sediment texture, and till origin, rather than glacier size or dynamics. Even small glaciers (1–2 km²) with short transport paths (2–3 km) are capable of effectively abrading and fracturing quartz grains. Under favorable conditions, well-preserved glacial microtextures from Middle Pleistocene mountain glaciers can still be detected. Detailed SEM analysis thus provides valuable insights into past glaciations and the minimum number of glacial cycles, even in moderately glaciated mountain regions.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"486 ","pages":"Article 106937"},"PeriodicalIF":2.7,"publicationDate":"2025-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144695179","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":"Fine-grained sediments down-sagging into coarse-grained substrate: A new category of soft-sediment deformation structures and their paleoseismological implications","authors":"Yong Sik Gihm ,&nbsp;Youngbeom Cheon ,&nbsp;Kyoungtae Ko","doi":"10.1016/j.sedgeo.2025.106936","DOIUrl":"10.1016/j.sedgeo.2025.106936","url":null,"abstract":"<div><div>This study investigates a novel type of soft-sediment deformation structures (SSDS), here termed “down-sagging sediments”, characterized by the downward penetration of less dense sediments into denser sediments. This type of SSDS was identified within fluvial sedimentary successions excavated at the epicentral region of the 2017 Pohang Earthquake and two trench sites (Inbo and Yanggok) in the Korean Peninsula. This study investigated the donw sagging sediments to unravel the morphological characteristics and forming-processes together with their potential as paleoseismological indicators. Down-sagging sediments developed along boundaries between overlying sandy mud and underlying sand (Pohang and Yanggok) or overlying mud and underlying sandy mud (Inbo). These down-sagging sediments show two main varieties: (1) vertically connected bodies maintaining physical continuity with overlying fine-grained sediments and (2) detached fine-grained bodies enveloped by underlying sand or sandy mud. Vertically connected bodies formed through the passive downward penetration of overlying less dense mud into void space created by upward expelled sediments via fluidization. Subsequent disintegration of the vertically connected down-sagging mud by fluidized sediments is responsible for the formation of the detached down-sagging sediments. Although the present study interpreted these structures to have been formed by seismic shaking, they can potentially form at any sediment interface where fluidization is the dominant deformation mechanism. Nevertheless, at the epicentral region of the 2017 Pohang Earthquake where &gt;600 sand blows formed on alluvial plains following the earthquake, the systematic vertical zonation–progressing from upper connected down-sagging sediments with detached ones having highly irregular margins to lower detached down-sagging sediments with smooth margins–may have been formed by two sequential processes: 1) down-sagging and subsequent disintegration during the mainshock, followed by 2) frictional abrasion of the disintegrated down-sagging sediments within underlying re-liquefied sand possibly as a result of forward and backward motions during aftershocks. This sequential development pattern may represent seismic events characterized by mainshock followed by aftershocks, suggesting their potential utility as paleoseismological indicators.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"486 ","pages":"Article 106936"},"PeriodicalIF":2.9,"publicationDate":"2025-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144722517","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":"Transgressive vs. forced regressive peat accumulation: Response of fluvial-apron peatland floodplains to aggradational transgression vs. forced regression","authors":"Jincheng Liu ,&nbsp;Yan Zhang ,&nbsp;Jingqiang Tan ,&nbsp;Daiyong Cao","doi":"10.1016/j.sedgeo.2025.106935","DOIUrl":"10.1016/j.sedgeo.2025.106935","url":null,"abstract":"<div><div>Previous work suggests the possibility that peat accumulation during relative sea-level (RSL) fall may be more common in the Quaternary and geological records than is currently commonly assumed. We investigate this further based on sequence stratigraphic analysis of successive coal-bearing cyclothems from the North China Permo-Carboniferous cratonic basin. The results show that each cyclothem changes basinward from a purely fluvial sequence to a mixed marine–nonmarine sequence. It is bounded by maximum regressive surfaces, correlative paired regional composite scour and interfluvial exposure surfaces farther landward, and correlative combined wave-ravinement and maximum regressive surfaces farther basinward. Temporally, each cyclothem transitions from a transgressive through highstand to falling-stage systems tract directly followed by the transgressive systems tract of the next cyclothem without an intervening lowstand systems tract. Depending on geomorphic conditions and characteristics of RSL rise or fall, the downstream fluvial reaches during transgression can be dominated by fluvial-fan or delta-plain channel aggradation, estuarine valley degradation, or lagoonal or fluvial-apron floodplain aggradation, or they transition from one to another. The downstream fluvial reaches during forced regression typically transition from delta plain degradation-inclusive through strandplain grade to fluvial apron aggradation-sustainable. Peat accumulation can be sustained only in fluvial-apron peatland floodplains during aggradational transgression or aggradational forced regression. Forced regressive fluvial-apron floodplain coal seams typically exhibit an overall upward decrease in mineral, ash, inertinite and sporinite contents and groundwater index, along with an increase in vitrinite content, gelification, tissue preservation and vegetation indices. Reverse trends of these properties characterize transgressive fluvial-apron floodplain coal seams.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"486 ","pages":"Article 106935"},"PeriodicalIF":2.7,"publicationDate":"2025-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144614166","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":"Late Paleozoic coastal plain paleosols: Geochemical insights into soil genesis, provenance, and paleoclimate within paleoequatorial Pangea, Paradox Basin, USA","authors":"Stephanie J. White ,&nbsp;Gary E. Stinchcomb ,&nbsp;Stacy C. Atchley ,&nbsp;Stephen I. Dworkin","doi":"10.1016/j.sedgeo.2025.106934","DOIUrl":"10.1016/j.sedgeo.2025.106934","url":null,"abstract":"<div><div>Studies of ancient drylands can enhance our understanding of ecosystem responses to changing climate, but reconstructing deep-time dryland environments using paleosols is challenging because these fossil soils are often weakly developed and many proxies are not equilibrated to past climate. Paleosols from the uppermost Honaker Trail Formation and lower Cutler beds (Rico and Halgaito Formations) span the Pennsylvanian-Permian transition within the Paradox Basin of southeast Utah (USA) and are an ideal setting to explore dryland paleoenvironments. Integration of bulk oxide, micro-XRF, and stable isotopic data allows for assessments of paleoclimate, provenance, and pedogenic processes. Ti/Al ratios track a broadly consistent provenance while Ti/Zr trends follow allochthonous dust contributions, possibly indicating a shift in paleowinds near the Rico-Halgaito boundary that is supported by Ti/Zr and Zr/Hf ratios from within-zircon analysis. Carbon isotopic data suggest pedogenic carbonate formation under conditions of low soil productivity while modeled MAP estimates reveal an average of 409 mm/yr ± 209. Evaluation of MAT and MAP relationships suggests that Inceptisols identified within this study could represent ancient Aridisols. We conclude that dry climatic conditions promoted an unstable landscape for the region encompassing the study interval while also precluding hydrolysis and leaching, resulting in weakly developed paleosols with abundant carbonate features and red coloration. These findings are consistent with other work from the region, pointing to dry conditions and shifting paleowinds within paleoequatorial Pangea during the Pennsylvanian-Permian transition.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"486 ","pages":"Article 106934"},"PeriodicalIF":2.7,"publicationDate":"2025-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144670520","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":"Late Quaternary oceanographic controls on sediment distribution and transportation in the Southeast Indian Ocean; insights from IODP Site U1516","authors":"Maqsood Ur Rahman ,&nbsp;Tao Jiang ,&nbsp;Muhammad Sarim ,&nbsp;Qianru Wang ,&nbsp;Cong Cheng","doi":"10.1016/j.sedgeo.2025.106930","DOIUrl":"10.1016/j.sedgeo.2025.106930","url":null,"abstract":"<div><div>The Late Quaternary is a crucial period marked by glacial-interglacial cycles that significantly impacted global paleoceanography and paleoclimate, making the reconstruction of terrigenous input in the southeastern Indian Ocean vital for understanding these shifts. We present a terrigenous sediment record from International Ocean Discovery Program Site U1516 in the offshore Mentelle Basin, reconstructing sediment provenance, transport mechanisms, and paleoclimate variability over the last 766 ky (MIS18-1). Grain-size analysis reveals a silt-dominated assemblage, with median grain size coarsening during glacial periods, reflecting enhanced winnowing of fine particles, while elevated clay concentrations suggest greater resistance to winnowing and increased supply from shallow shelves due to sea-level decline. Clay mineral assemblages show dominance of kaolinite and illite during interglacials, contrasting with peaks in smectite and chlorite during glacials. These patterns are attributed to sources in southwestern Australia transported by the Leeuwin Current, which delivered more kaolinite and illite during intensified interglacials and shifted to finer-grained smectite during weakened glacials. Elevated chlorite during glacials likely derives from deep marine settings south of Australia or Antarctica, transported via Antarctic Intermediate Water and Leeuwin Undercurrent. This variability highlights glacial-interglacial shifts in sediment routing tied to ocean circulation changes. Contrary to earlier observations of ‘dry glacials’ in southern Australia, data from Hole U1516B (illite crystallinity, chemical indices) reveal the presence of both wet and dry periods during glacials that were previously assumed to be solely dry, aligning with speleothem records but conflicting with bulk geochemical interpretations. This highlights the need for proxy-specific calibration. Interglacial periods also show intensified wetter intervals similar to those during glacials. These glacial-interglacial wetter intervals are likely driven by latitudinal shifts in the Southern Hemisphere westerly winds. This study provides new insights into glacial-interglacial transitions, linking oceanic circulation shifts, sediment transport dynamics, and hydroclimate variability in southwest Western Australia.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"486 ","pages":"Article 106930"},"PeriodicalIF":2.7,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144580848","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":"Giant lacustrine bioherms in the northeastern Qinghai-Tibet Plateau (western Qaidam Basin) during the Early–Middle Miocene: Carbonate fabrics, growth patterns, and environmental significance","authors":"Hui Xie ,&nbsp;Fei Li ,&nbsp;Xiang Li ,&nbsp;Jiangong Wang ,&nbsp;Chaojin Lu ,&nbsp;Yuefeng Shen ,&nbsp;Yalan Li ,&nbsp;Zengjun Wang ,&nbsp;Tianshu Zhang ,&nbsp;Yangfan Li ,&nbsp;Tao Wu ,&nbsp;Ying Li","doi":"10.1016/j.sedgeo.2025.106932","DOIUrl":"10.1016/j.sedgeo.2025.106932","url":null,"abstract":"<div><div>The development of lacustrine carbonate bioherms in the Qaidam Basin provides critical insights into the influence of the Qinghai-Tibetan Plateau (QTP) uplift and climate change on Asian interior lake ecosystems. Two distinct, successively developed phases of carbonate bioherm proliferation, each extending laterally for over 3 km, have been identified within the Lower to Middle Miocene siliciclastic-dominated strata of the western Qaidam Basin, northeastern Tibetan Plateau. These bioherms exhibit diverse morphologies—ranging from large domical structures (&gt;3 m high) to smaller hemispherical and inverted conical forms (&lt;1 m)—and are arranged either as biostromes within a single stratigraphic level or in complex, vertically stacked patterns. Green algae (<em>Cladophorites</em> and problematic <em>Chlorellopsis</em>) and putative calcimicrobes were the primary bioherm builders. The dominant alga <em>Cladophorites</em> primarily formed radially branching and dense-reticular frameworks. Putative calcified filamentous and spherical microbes, acting alone or in association with green algae, formed foundational cores or substrates. These were subsequently encased by stromatolitic crusts, which aggraded iteratively from lithified microbial mats via microbially induced mineralization. The frameworks contain abundant microsparitic (4–30 μm) calcite crusts and laminated fibrous calcite cements, complemented by fringing dolomite cement crusts at the margins; these features collectively enhanced the lithification and preservation of the bioherm structures. Through multi-scale petrographic and sedimentological analysis, ten distinct lithofacies were identified within the bioherms and adjacent strata. Based on the spatial and temporal distribution of these lithofacies, a three-stage evolutionary model is proposed for the bioherms, which includes: (1) an initiation stage on littoral quartz sand bars and ooid/peloid shoals; (2) a development stage during a gradual transgression; and (3) a termination stage marked by the deposition of littoral muds or distal sublittoral silts. The proliferation of large, algal-microbial bioherms in the plateau-type Qaidam Basin required a specific set of environmental conditions: warm, fresh-to-brackish waters, sufficient accommodation space, high alkalinity, and abundant nutrients. We propose a model highlighting the integrated effects of an enhanced hydrological cycle across the QTP, catalyzed by the Miocene Climatic Optimum. The spread of these carbonate bioherms into the typically cold, arid, and saline lacustrine environments of the QTP serves as a significant indicator of this extreme warming event, providing valuable insights into potential biological and sedimentological feedback mechanisms under analogous present-day warming conditions.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"486 ","pages":"Article 106932"},"PeriodicalIF":2.7,"publicationDate":"2025-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144695180","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":"Constructive and destructive processes affecting a tufa system in semi-arid Sierras Pampeanas, Argentina","authors":"Santiago Centorbi ,&nbsp;R. Agustin Mors ,&nbsp;Ricardo A. Astini ,&nbsp;Fernando J. Gomez ,&nbsp;Brenda Y. Alvarez","doi":"10.1016/j.sedgeo.2025.106931","DOIUrl":"10.1016/j.sedgeo.2025.106931","url":null,"abstract":"<div><div>This study focuses on a modern tufa system developing under a semi-arid climate at mid-latitude in the Sierras Pampeanas of central Argentina, currently undergoing degradation. The research integrates a geomorphological, sedimentological, mineralogical, and hydrochemical approach to analyze constructive and destructive processes in tufa systems and their preservation potential in the stratigraphic record. The tufa features a 12.2-m-high, semi-conical structure, perched in a waterfall at the confluence of the Los Quebrachitos stream and Cabana River, overlying crystalline basement rocks rich in marble belts. The main lithofacies identified are: biohermal tufa, laminated tufa crusts, sandy tufa. Additionally, rubble tufa deposits occur at the base of the waterfall. Biohermal tufas are dominated by phytohermal components and associated invertebrate remains, with irregular clotted-micrite and peloidal fabrics. At the microscale, microbial activity becomes more significant, where cyanobacteria, diatoms, and exopolymeric substances contribute to the development of irregular laminated fabrics. Laminated tufa crusts consist of alternating micritic, microsparitic, and sparitic low-Mg calcite layers. The Los Quebrachitos stream, classified as fresh (total dissolved solids between 81.57 and 79.5 mg/L), slightly alkaline (pH between 7.9 and 8.3) waters, has a calcium-bicarbonate composition (Ca²⁺ between 23.10 and 26.16 mg/L, carbonate alkalinity between 95.95 and 112.18 mg/L). Flow rate variations, due to rainfall, appear to control the carbonate saturation state of waters in the Los Quebrachitos system. During dry season, the combined effects of aeration, low pressure, and jet flow enhance CO₂ degassing, enabling slightly saturated conditions with respect to calcite (Ω_cal = 1.1), promoting tiny water droplets evaporation, and thereby, inducing calcite precipitation. Conversely, increased rainfall dilutes water, reducing total dissolved solids and calcite saturation. Currently, the tufa system is in a destructive phase, showing gravitational collapse, bio-fracturing from tree root colonization, and surface erosion-dissolution features. The ongoing destructive processes seem to exceed the precipitation rates in this depleted carbonate system, mainly due to changes in climate conditions.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"486 ","pages":"Article 106931"},"PeriodicalIF":2.7,"publicationDate":"2025-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144589079","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":"High-resolution sequence stratigraphy of Upper Jurassic lacustrine cycles in the Parnaíba Basin, Brazil: Unraveling basin evolution through climate and thermal subsidence","authors":"Argel de Assis Nunes Sodré ,&nbsp;Afonso César Rodrigues Nogueira ,&nbsp;Juliana Charão Marques ,&nbsp;João Vicente Tavares Calandrini de Azevedo ,&nbsp;Renan Fernandes dos Santos ,&nbsp;Luiz Saturnino Andrade ,&nbsp;Leandro Freitas Sepeda ,&nbsp;Pedro Guilherme Assunção Oliveira","doi":"10.1016/j.sedgeo.2025.106933","DOIUrl":"10.1016/j.sedgeo.2025.106933","url":null,"abstract":"<div><div>Palaeolakes of the Late Jurassic, in West Gondwana, were critically shaped by thermal subsidence, driven by isostatic adjustment, isotherm downgrading, and the cooling of mafic magma associated with the Central Atlantic Magmatic Province (CAMP) around 201 Ma. These key processes are recorded in the Pastos Bons Formation, located within the Parnaíba Basin in northeastern Brazil. Although this sedimentary succession has recently been examined from a palaeoenvironmental perspective, a significant gap remains in characterizing its stacking patterns through the lens of high-resolution sequence stratigraphy (HRSS). Therefore, there remains a lack of clarity regarding the interplay between climatic and thermal subsidence and its influence on sedimentation and lake level fluctuations. Hence, we identified twenty sedimentary facies, grouped into six facies associations: central lake (FA1), hyperpycnal littoral delta (FA2), lakeshore (FA3), alluvial fan (FA4), fluvial (FA5), and delta front (FA6). The HRSS framework reveals three medium-frequency sequences, representing clusters of high-frequency T-R (transgressive-regressive) sequences, controlled by long-term climatic changes: sequence-1 (Seq-1), sequence-2 (Seq-2), and sequence-3 (Seq-3). Seq-1 and Seq-2 exhibit a higher proportion of transgressive system tract (TST) than regressive system tract (RST), and they demonstrate dramatic fluctuations in lake level. In contrast, Seq-3 shows a predominance of the regressive systems tract (RST) over the transgressive systems tract (TST), reflecting greater stability in lake level. The medium-frequency framework reveals that the Pastos Bons Formation is characterized by a balanced-fill lacustrine basin (Seq-1 and Seq-2) overlaid by an overfilled lacustrine basin (Seq-3). The low-frequency chronostratigraphic framework, composed of clusters of medium-frequency T-R sequences (seismic scale), indicates that post-CAMP thermal subsidence presents a primary control on the configuration, size, shape, and accommodation potential of the lacustrine basin. Post-CAMP subsidence along the Equatorial Atlantic margins during the Late Jurassic period played a key role in shaping the palaeogeography of West Gondwana, promoting the development of lacustrine basins.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"486 ","pages":"Article 106933"},"PeriodicalIF":2.7,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144604350","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}