Sedimentary Geology最新文献

{"title":"High-resolution isotopic records for the last 200 years from cascade tufas on Kobaru Beach, Tokunoshima Island, Japan","authors":"Akira Murata ,&nbsp;Akihiro Kano ,&nbsp;Aki Sakuma ,&nbsp;Hirokazu Kato","doi":"10.1016/j.sedgeo.2025.106949","DOIUrl":"10.1016/j.sedgeo.2025.106949","url":null,"abstract":"<div><div>A stromatolitic tufa with annual growth bands and a large growth rate is a promising archive for high-resolution paleoclimate reconstruction. However, a tufa formed in a fluvial setting typically lacks continuity of deposition. To obtain a continuous record, a potential study material is a cascade-type tufa growing below a waterfall. Here, we study tufas along Kobaru Beach on Tokunoshima Island, Japan, where cascade-type tufas are developed. Oxygen and carbon isotope ratios (δ¹⁸O and δ¹³C) of tufa samples collected from three sites with different sedimentary settings provide information about precipitation patterns and water temperature. A tufa sample from a fluvial setting exhibits clear annual growth rings, rapid growth rates, and seasonal changes in isotopic composition over approximately 20 years. Tufas of the stalagmite-type and cascade-type, having less clear annual growth rings and lower growth rates, preserve continuous records over the last 200 years, the longest record from the modern tufas. The δ¹³C of the cascade-type tufa shows a decreasing trend from the 1980s, which is interpreted as a result of fossil fuel consumption and an increase in rainfall. In addition, the δ¹³C of the cascade-type tufa tends to increase in dry intervals and decrease in humid intervals. On the other hand, an approximately 20-year periodicity is observed in the δ¹⁸O. Analysis of rainwater samples implies that the δ¹⁸O of tufa reflects the seasonality of rainfall, which is inherited from the rainwater δ¹⁸O. This interpretation is verified by the consistency between the actual record and the seasonality reconstructed by the tufa δ¹⁸O. While cascade-type tufas do not provide sub-annual resolution, they serve as valuable centennial-scale climate archives, which allow us to investigate decadal-scale climate variability, such as Pacific Decadal Oscillation.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"487 ","pages":"Article 106949"},"PeriodicalIF":2.9,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144879912","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":"Signatures of hydraulic jump-related scouring in a deep-marine rift basin, Wollaston Forland Group, NE Greenland","authors":"Sten-Andreas Grundvåg ,&nbsp;Gijs A. Henstra ,&nbsp;Atle Rotevatn ,&nbsp;Eric Salomon ,&nbsp;Thomas Berg Kristensen","doi":"10.1016/j.sedgeo.2025.106944","DOIUrl":"10.1016/j.sedgeo.2025.106944","url":null,"abstract":"<div><div>Supercritical high-density turbidity currents descending steep submarine slopes often transition to subcritical flow via hydraulic jumps at the base-of-slope break, causing scouring and plunge pool formation. On the slope, scour arrays from turbulent erosion by the flow head, can develop into chutes where supercritical flow is sustained, generating cyclic steps. However, little is known about the infill of hydraulic-jump-related scours and upper flow regime bedforms in coarse-grained, deep-water slope systems. This study examines conglomerate- and sandstone-rich sediment gravity flow deposits from an Upper Jurassic–Lower Cretaceous deep-water <em>syn</em>-rift succession in Wollaston Forland, NE Greenland. These coarse-grained deposits accumulated on a steep, subaqueous fan delta slope perched on the basin-bounding fault escarpment. The upper slope, with minimal scouring, is dominated by breccia and conglomerate beds from debris falls and non-cohesive debris flows. In contrast, the lower slope exhibits extensive scouring, diverse scour-and-fill elements, and complex bedding patterns suggesting hydraulic jump-related erosion and scour filling by strongly stratified, supercritical high-density turbidity currents. Arrays of asymmetric conglomeratic scour fills, frequently exhibiting variably inclined and laterally accreted stratification, may indicate the presence of cyclic steps. Abundant conglomerate-filled scours at the slope base further suggest that gravel from the basal, inertia-driven part of the flows were trapped in plunge pools carved by their faster-moving turbulent parts. The dominance of sandstone beds on the basin floor indicates that the sand-laden turbulent flows continued basinward before coming to rest. Our findings highlight the role of flow transformation and scouring in shaping submarine slopes and controlling deep-water architecture.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"487 ","pages":"Article 106944"},"PeriodicalIF":2.9,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144865275","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":"2025-08-01","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":"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":"2025-08-01","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":"Depositional facies, sequence stratigraphy and diagenesis of the Cambrian-Middle Ordovician siliciclastic outcrops, Tayma Region, NW Saudi Arabia: An integrated approach for reservoir characterization","authors":"Sultan A. Almalki ,&nbsp;Hamdalla A. Wanas ,&nbsp;Faisal Alqahtani ,&nbsp;Murad R. Abdulfarraj","doi":"10.1016/j.sedgeo.2025.106928","DOIUrl":"10.1016/j.sedgeo.2025.106928","url":null,"abstract":"&lt;div&gt;&lt;div&gt;This study explores how integrating depositional facies, sequence stratigraphy, and diagenetic attributes from outcropped siliciclastic rocks can enhance the characterization of reservoirs in a siliciclastic system. The Cambrian–Middle Ordovician siliciclastic outcrops in the Tayma region of northwestern Saudi Arabia are used as a case study to address this integrative approach. This represents the first integrated study of its kind for the Tayma region. The rationale for this choice is addressed herein. This work has been achieved through detailed field observations accompanied by petrographic, X-ray diffraction, and petrophysical analyses. The studied stratigraphic successions comprise the Saq Formation (the Risha and Sajir members) and the lower members of the Qassim Formation (the Hanadir and Kahfah members). Based on field observation, sixteen lithofacies were identified and grouped into six facies associations. These lithofacies and their related facies associations reflect deposition in braided fluvial, tidally influenced fluvial (upper estuarine), foreshore-upper shoreface, lower shoreface, lower shoreface-offshore transition, and offshore environments. The stacking pattern of the inferred facies and their facies associations led to the subdivision of the studied successions into three superimposed depositional sequences, including highstand-, lowstand-, and transgressive-systems tracts. Petrographic analyses indicate that the studied sandstones are primarily quartz arenites, subarkose arenites, and quartz wackes. These sandstones contain detrital components with different grain textures ranging from poorly to well sorted, subrounded to rounded, and fine- to coarse-grained. The sandstones underwent both shallow and deep burial diagenesis, including compaction, carbonate and iron cementation, clay authigenesis (kaolinite, dickite, and illite), quartz overgrowth, and dissolution of unstable feldspar and mica grains.&lt;/div&gt;&lt;div&gt;The integration of the above findings reveals that fluvial-related sandstones linked to lowstand systems tracts (LSTs), along with diagenetic features such as dissolution, mechanical compaction and partial overgrowths) display characteristic features of superior reservoir quality. In contrast, marine-related sandstones (foreshore-shoreface–offshore transition and offshore/shelf environments), typically linked to transgressive (TSTs) and highstand systems tracts (HSTs), along with diagenetic features such as cementation, illite-smectite authigenesis, and complete silica overgrowths exhibit relatively lower reservoir quality at various scales. The reasons behind these findings are discussed herein. In this context, the offshore facies of the Hanadir Shale, which are part of the transgressive systems tract (TSTs), can be recognized as potential source rocks. As a result, this study highlights that reservoir quality in siliciclastic systems is primarily controlled by depositional facies, sequence stratigraphic co","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"486 ","pages":"Article 106928"},"PeriodicalIF":2.9,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144780819","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":"2025-08-01","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":"Astronomical time scale and stratigraphic division constrained by the Milankovitch cycles and SPICE event in the Cambrian of the Xuzhou, Jiangsu Province","authors":"Zhiying Dang ,&nbsp;Yulin Shen ,&nbsp;Zuchao Wen ,&nbsp;Zhuangfu Li ,&nbsp;Feiyang Chen ,&nbsp;Yan Meng ,&nbsp;Tianyang Yang ,&nbsp;Yuhong Jing","doi":"10.1016/j.sedgeo.2025.106927","DOIUrl":"10.1016/j.sedgeo.2025.106927","url":null,"abstract":"<div><div>The lack of high-precision age constraints for the internal age of the Cambrian in North China has always affected the research and comparison of Cambrian strata worldwide. This study, using magnetic susceptibility data from the Cambrian strata of the Xuzhou area, identifies Milankovitch cycles within the sedimentary strata. By utilizing stable carbon isotope excursion curves, the lower Furongian in the study area was discerned to exhibit a Steptoean positive carbon isotope excursion (SPICE) event, lasting ∼1.6–1.8 Myr, with a peak age constrained to 494.6 ± 2.9 Ma. Using in situ Rb<img>Sr dating from glauconite grains in the base of the Mantou Formation (Stage 4), the stratigraphic age was constrained to about 513 Ma. By anchoring the identified 405-kyr calibration time series to these two ages, a relatively high-resolution astronomical time scale was constructed. The results indicate that the Cambrian Stage 4 to early Stage 10 in the Xuzhou area of North China spans from 512.30 ± 2.9 Ma to 490.03 ± 2.9 Ma, with a duration of 22.27 ± 0.2 Myr. Specifically, the basal ages of the Mantou Formation (Series 2 to Miaolingian Series; Stage 4 to early Drumian stage), Zhangxia Formation (Miaolingian to Furongian Series; early Drumian to middle Paibian stage), and Chaomidian Formation (Furongian Series; middle Paibian to early Stage 10) were determined to be 512.30 ± 2.9 Ma, 504.00 ± 2.9 Ma, and 495.74 ± 2.9 Ma, respectively, with durations of 8.30 ± 0.2 Myr, 8.26 ± 0.2 Myr, and 5.71 ± 0.2 Myr. This series of studies not only standardized the classification of lithostratigraphic units in the Xuzhou area, but also provided precise chronological evidence for exploring the climatic-biota-environmental ecological evolution during the Cambrian period.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"486 ","pages":"Article 106927"},"PeriodicalIF":2.7,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144501669","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":"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":"Refined Os isotope stratigraphy of ferromanganese crusts from the Arctic Ocean and implications for polar environmental change since the late Miocene","authors":"Natalia Konstantinova ,&nbsp;James R. Hein ,&nbsp;Liang Yi ,&nbsp;Yu Liu ,&nbsp;Hiroyuki Matsuzaki ,&nbsp;Qing Chang ,&nbsp;Akiko Makabe ,&nbsp;Harald Brekke ,&nbsp;Sergei Skolotnev ,&nbsp;Georgy Cherkashov ,&nbsp;Katsuhiko Suzuki","doi":"10.1016/j.sedgeo.2025.106942","DOIUrl":"10.1016/j.sedgeo.2025.106942","url":null,"abstract":"<div><div>The long-term environmental history of the Arctic region remains restricted due to the limited number of pre-Quaternary sedimentary records. We present the first Os isotope data of hydrogenetic ferromanganese crusts collected from four locations in the Arctic Ocean: Northwind Ridge, Mendeleev Ridge, Knipovich Ridge and Voring Spur; water depth varied from 1300 to 3851 m. The Os concentrations, ¹⁸⁷Os /¹⁸⁸Os ratios, and major- and trace-element compositions of sublayers (2–5 mm thick) show clear temporal variations. Be isotope ages determined for the Mendeleev Ridge crust were used to guide the ¹⁸⁷Os /¹⁸⁸Os ages of the Fe<img>Mn crusts, which were obtained by comparison of the ¹⁸⁷Os /¹⁸⁸Os ratios in the crusts with those of the Cenozoic seawater curve. The results greatly improve the Arctic Os isotope temporal record from Fe<img>Mn crust stratigraphy for the late Miocene and Quaternary.</div><div>Several groups of elements show similar behavior spatially (predominantly Ti, Ba, U, REE, Y, Nb, Hf, Cd, Zr, and Ni, Cu) and two groups temporally (Fe, V, As and Ca, Co, Pb, Th). The temporal history is characterized by variations in radiogenic Os isotope composition, which were associated with the long-term (&gt; 10⁵ yr) climatic trends in the region, such as late Miocene cooling, early-to-middle Pliocene warming, and Pliocene-Pleistocene Northern Hemisphere glaciation. The Fe<img>Mn crust growth rate decreased drastically in the late Miocene possibly due to changes in bottom water conditions associated with the final widening and deepening of the Fram Strait.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"486 ","pages":"Article 106942"},"PeriodicalIF":2.9,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144829085","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":"2025-08-01","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}