Sedimentary Geology最新文献

{"title":"Debris aggregates in debris flows and implications for debris-flow dynamics","authors":"Yi-Xi Wen ,&nbsp;Ze-Min Xu ,&nbsp;Xiao Su ,&nbsp;Bin Li ,&nbsp;Zi-Ming Ye ,&nbsp;Gui-E Shi ,&nbsp;Jing-Kai Meng","doi":"10.1016/j.sedgeo.2025.106946","DOIUrl":"10.1016/j.sedgeo.2025.106946","url":null,"abstract":"<div><div>Sediments related to debris flows consist usually of single clasts of various sizes. A kind of composite debris, i.e., elongate debris aggregates, occurring in the Jiangjia Gully debris flows in China, is reported herein. They can occur as isolated individuals, and more commonly as clusters of a few to several hundred individuals. 2,225 measured aggregates vary in maximum and minimum dimensions from 2 to 187 cm (average 17 cm) and from 2 to 107 cm (mean 12 cm), respectively. The aggregates with an elongation ratio of ≤ 0.8 make up 63%, fat ones having a flatness ratio of ≤ 0.8 represents only 37%, and at least 53% of the aggregates are prolate spheroidal. The average convexity of 0.92 illustrates that the aggregate surfaces are smooth. Massive structure (sometimes with cobble cores), concentrically banded structure, and deformation structure are developed in aggregate interiors. Slate clasts ranging in size from clay to cobbles, which originate from landslide debris in the debris-flow source areas and moving debris-flow slurries, comprise the aggregates. Field observations of more than 30 surges show that most of the aggregates belong to the objects transported by the debris flows, and rolling process is essential to their development. Fibrous palygorskite, which acts as the rock-forming mineral of the slate bedrock and is released by slate detritus, is responsible for the widespread occurrence of the aggregates. The marked presence of the elongate aggregates indicates that the debris flows can be approximated as one-dimensional, laminar flow of homogeneous single-phase yield stress fluids. Debris aggregates in debris flows merit attention because of their significant implications for debris-flow dynamics and of facilitating sediment transfer.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"488 ","pages":"Article 106946"},"PeriodicalIF":2.9,"publicationDate":"2025-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144912003","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":"2025-08-05","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":"From Platform to Burial: Tectonic and climatic imprints on the diagenetic evolution of shallow-marine carbonate deposits (Middle Eocene), Bombay Offshore Basin, India","authors":"Sreetama Aich ,&nbsp;Cathy Hollis ,&nbsp;Sudipta Dasgupta ,&nbsp;Kumar Hemant Singh","doi":"10.1016/j.sedgeo.2025.106940","DOIUrl":"10.1016/j.sedgeo.2025.106940","url":null,"abstract":"<div><div>Conventional cores collected from a shallow tropical carbonate-ramp system reflect a diagenetic pathway that was influenced by both the globally humid, tropical climate at the middle Eocene time and the subsequent onset of Himalayan mountain building. Detailed optical, cathodoluminescence-petrographic and non-isotopic geochemical analyses were used for the study. The eogenetic processes, e.g., micritization, pyritization, isopachous and micritic cementation, early marine dolomitization, and the early stages of mechanical compaction, happened during and soon after deposition in the marine-phreatic environment. During the late Eocene, as the global climate cooled, the relative sea level fell, and the carbonate ramp underwent subaerial exposure, leading to the meteoric-phreatic diagenetic processes, e.g., neomorphism, dissolution (phase-1), pendant cementation (vadose zone), and significant calcite spar cementation (C-1). With ensuing deposition above through the early Oligocene, the effects of compaction affected the formation by truncation and fragmentation of grains, condensed packing, developing various (point-tangential, concavo-convex, and sutured) grain contacts, pressure dissolution and stylolite generation, fracturing, corrosion (phase-2 dissolution), and burial-calcitic (C-2) and non-calcitic (NC) cementation. After the early Oligocene, the basin tilted westward, a far-field consequence of the Indo-Eurasian collision. This tectonic reorganisation caused the Paleogene carbonate strata to undergo a partial exhumation and thus, they were susceptible to the influence of meteoric water mainly through the reactivation of pre-existing faults. These tectonic readjustments led to the reopening of the stylolite sets, telogenetic fracturing, and another dissolution episode (phase 3). Hence, the diagenetic pathway manifesting itself at the microscopic scale posits a clear connection with the basin's evolution. Further, the diagenetic reconstruction also corroborates the global climatic transition, from a greenhouse to a cooler ice-house condition, that took place across the Eocene-Oligocene boundary, making the study significant from a regional to global scale.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"488 ","pages":"Article 106940"},"PeriodicalIF":2.9,"publicationDate":"2025-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144916613","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":"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":"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":"Tectono-eustasy and basin morphology controls on Cretaceous facies architecture in the northeastern margin of Arabian Plate","authors":"Borhan Bagherpour ,&nbsp;Ali Faghih ,&nbsp;Hossein Vaziri-Moghaddam ,&nbsp;Hamzeh Mehrabi ,&nbsp;Mehdi Zare ,&nbsp;Adrian Immenhauser","doi":"10.1016/j.sedgeo.2025.106943","DOIUrl":"10.1016/j.sedgeo.2025.106943","url":null,"abstract":"<div><div>Basement highs and adjacent basins are significant structural elements controlling regional facies architecture. Overprinted by fluctuating sea-levels, the correlation of facies units from the crest into the flank environments is often challenging. Here, a case example of an upper Turonian–lower Campanian palaeohigh on the northeastern margin of the Arabian Plate is presented. Two stratigraphic sections (Jarhum and Qazi, respectively) compare the depositional dichotomy between crest and flank. The palaeohigh Jahrum section documents a deepening upward succession that includes brackish carbonates at the base, followed by shallow–marine carbonates, and culminates in basinal deposits. The sedimentary record of Santonian deposits in the Qazi section (flank) comprises stratigraphically thick calciturbidites, calcidebrites, slump folding, clinoforms, and channel-fill deposits, which conformably overlie deep-water deposits. This case study provides insights into processes that are rarely documented in the Tethyan realm. Data shown here exemplify the interaction between regional uplift (related to tectonic inversion) and eustatic sea–level changes. The regional correlation of the facies architecture highlights important lateral variations in facies and stratigraphic thickness controlled by bathymetry and seafloor inclination related to the geometry of the palaeohigh. We suggest that the redeposited carbonates described here are characteristic of tectonically active intervals along slope settings. Furthermore, we demonstrate that sustained carbonate production on unrimmed, distally steepened ramps supports the deposition of calciclastics. The data presented are crucial for understanding redeposition processes in Cretaceous carbonate systems along the Arabian margin and beyond.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"486 ","pages":"Article 106943"},"PeriodicalIF":2.9,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144809661","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}