Sedimentary Geology最新文献

{"title":"Analysis of lake level fluctuations in the Early Cretaceous Songliao Basin supports aquifer eustacy","authors":"Zilong Wang,&nbsp;Shaobin Guo","doi":"10.1016/j.sedgeo.2024.106770","DOIUrl":"10.1016/j.sedgeo.2024.106770","url":null,"abstract":"<div><div>Clear geochronology and precise interpretation of sequence stratigraphy enhance our understanding of continental lake-level evolution. The Songliao Basin features well-preserved Cretaceous continental strata. Nevertheless, the correlation between lake-level fluctuations and global sea-level changes remains ambiguous. High-resolution gamma ray logging data were used to analyze the cyclical stratigraphy of the lower member of the Early Cretaceous Shahezi Formation in the Songliao Basin. X-ray fluorescence experiments characterized the sedimentary environment of this formation. Lake-level variations in the lower part of the Early Cretaceous Shahezi Formation were reconstructed using sedimentary noise modeling based on finely tuned gamma ray logging data. Time series analysis using the tuned gamma ray data established an astronomical timescale of approximately 2.4 Myr within the lower section of the early Cretaceous Shahezi Formation in the Songliao Basin. A volcanic ash layer dating (118.20 ± 1.5) Ma from the base of the Shahezi Formation served as an anchor point, providing an absolute astronomical timescale ranging from 115.80 to 118.20 Ma for the study region. The sedimentary model indicates that variations in paleowater depth within the lower section of the Shahezi Formation closely match fluctuations observed in the Fe/Mn index, which reflects paleowater depth changes. This introduces a novel approach to assess changes in continental lake levels. The sedimentary noise model revealed a notable obliquity cycle of about 1.2 million years, strongly associated with fluctuations in lake levels. This indicates that prolonged obliquity periods affect lake level variations. Intriguingly, when lake levels rise, global sea levels concurrently decline, highlighting an inverse relationship between these phenomena. This observation offers insights into how long-term obliquity-driven climate changes regulate sea and lake levels.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"474 ","pages":"Article 106770"},"PeriodicalIF":2.7,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142655372","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":"Quantitative characterization on multistage formation of sedimentary pyrite driven by H2S derived from biogenic process in the northeastern Ordos Basin, China","authors":"Liang Yue,&nbsp;Yangquan Jiao,&nbsp;Liqun Wu,&nbsp;Hui Rong","doi":"10.1016/j.sedgeo.2024.106768","DOIUrl":"10.1016/j.sedgeo.2024.106768","url":null,"abstract":"<div><div>Negative δ³⁴S values of sedimentary pyrite associated with organic matter are routinely assumed to be the result of biogenic process. However, the distribution and evolution of isotopic values mediated by bacteria across sedimentary strata remains poorly understood. Abundant pyrite-rich nodules (PyRNs) are distributed in the bottom of the sandstone unconformably overlying the coal in middle Jurassic strata in the northeastern Ordos Basin, providing a good opportunity to quantitatively characterize the distribution, morphology and compositions of sulfur isotope and trace element of pyrite in the sandstone influenced by organic matter in the coal. A total of 1007 PyRNs occurs within a range of 4 m from the coal. From bottom to top in the sandstone, the shape of the nodule changes from oval to round on the vertical section, and the length and number gradually decrease at the rate of ~45 mm and ~ 228 for every 1 m increase in distance, respectively. Microscopically, pyrite occurs as euhedral crystals, and trace element mapping reveals multistage growth (up to a dozen times) and a marked compositional zoning with respect to Co, Ni, As, Se and Mo. The positive correlation between Co and Ni, with ratios of Co/Ni ranging from 0.06 to 0.45, indicates that Fe and those trace elements are sourced from diagenetic fluid. The organic sulfur in coal, serving as a sulfur source, is reduced by bacteria to generate H₂³²S at a slow reduction rate. The H₂³²S migrates upwards and reacts with Fe to form pyrite in the sandstone, resulting in extremely low δ³⁴S values (from −53.9 to −43.1 ‰), which gradual decrease both from core to margin in individual grain and at the rate of 2.2 to 8.8 ‰ for every 1 m increase in distance away from the coal. This study highlights the significant variability of mineralogical (e.g., number, size, morphology) and geochemical (trace elements, sulfur isotope) characteristics of sedimentary pyrite. Results allow the relation of multistage growth of pyrite to biogenic fractionation, and provide fresh insights into biogenically derived sulfur from coals to be fixed in sandstones, which can be applied to quantitative characterization of formation processes of sedimentary minerals controlled by organic matter in sedimentary environments worldwide.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"473 ","pages":"Article 106768"},"PeriodicalIF":2.7,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142658920","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":"Benthic response to event deposition and environmental disturbance in a shoreface to subaqueous delta system: Ichnology of the Silurian-Devonian Furada Formation of Asturias, Spain","authors":"Katherine Thue ,&nbsp;Luis A. Buatois ,&nbsp;M. Gabriela Mángano ,&nbsp;Mateo Ornia","doi":"10.1016/j.sedgeo.2024.106767","DOIUrl":"10.1016/j.sedgeo.2024.106767","url":null,"abstract":"<div><div>The Furada Formation of Asturias, Spain, represents a clastic shallow-marine unit deposited during the middle Silurian to the Early Devonian. This formation contains abundant evidence of event deposition and non-uniform distribution of bioturbation structures representing a benthic response to multiple stressors. The 170-m-thick succession was measured and described, and the ichnotaxa were recorded and associated with five sedimentary facies. Most shallow-marine environments are characterized by periodic events of environmental disturbance, mainly by episodic deposition, which may be recorded by a change in both the degree of bioturbation and ichnodiversity. The general depositional setting for this formation has been previously interpreted as a wave-dominated and storm-influenced shallow-marine environment. However, sedimentologic features described in this study, such as anomalous heterolithic and mudstone units, representing fluid mud layers, hyperpycnal flow deposits and plume collapse accumulations, suggest the influence of fluvial discharge, making it a more complex depositional setting. The proposed model comprises an inner sandy shoreface belt flanked seawards by a muddy subaqueous delta platform. The trace-fossil assemblages of this formation reflect environmental stress factors introduced by the interplay of storms and fluvial input (e.g., high sedimentation rate, fluctuating hydrodynamic energy, decreased substrate consolidation), resulting in reduced ichnodiversity and low abundance. From an ichnofacies perspective, the shoreface complex is characterized by the <em>Cruziana</em> Ichnofacies, whereas the subaqueous delta platform is represented by the <em>Phycosiphon</em> Ichnofacies. Integration of sedimentologic and ichnologic datasets allows for a refined depositional interpretation of the formation and greater understanding of the environmental diversity of wave-and river-influenced shallow-marine clastic systems, including the responses of the middle Paleozoic shallow-marine benthos to event sedimentation and environmental disturbance. This study is one of the first detailed documentations of the ichnology of subaqueous deltas.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"473 ","pages":"Article 106767"},"PeriodicalIF":2.7,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142658817","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Distribution of transitional flow deposits in sedimentary environments of mixed sand-mud turbidite system","authors":"Piotr Łapcik","doi":"10.1016/j.sedgeo.2024.106766","DOIUrl":"10.1016/j.sedgeo.2024.106766","url":null,"abstract":"<div><div>Predicting facies distribution in turbidite systems is essential for resource exploration and identifying geohazards from an economic standpoint. Models that describe facies distribution depend heavily on understanding the mechanisms of particle transport and deposition. These processes are closely tied to the volume, concentration, and composition of sediment gravity flows, which display a range of behaviours between turbulent and laminar flow extremes. Recently, there has been a rise in studies on transitional flow deposits, although they remain much less understood than fully turbulent or laminar flows.</div><div>For the first time, the distribution of Structured sandstone–mudstone associated with transitional flow deposits has been quantitatively presented for various sedimentary environments within the turbidite system. The distribution of Structured sandstone–mudstone was analysed for six areas of the Ropianka Fm (Skole Nappe, Polish Outer Carpathians) across twelve sedimentary environments, including channels, channel-levees, channel-mouths, and sub-environments of the depositional lobe. An increased amount of Structured sandstone–mudstone was observed in proximal settings away from the transport axis and in the distal parts of the turbidite system. It was found that flow transformation can occur in both proximal and distal zones of the turbidite system. Structured sandstone–mudstone in proximal zones is more often deposited from diluted mud-laden flows of small volume, where fine-grained cohesive material likely underwent vertical segregation. In contrast, Structured sandstone–mudstone formed basinward tend to be initially formed by larger flows. In proximal part of depositional lobe setting, the flow transformation due to longitudinal or longitudinal and vertical segregation of fine-grained cohesive material occurs slowly. At this point the velocity of sediment gravity flow is too high and the concentration of cohesive particles is too low for common development of cohesive bonds. Flow transformation accelerates in lobe fringe and lobe distal fringe/interlobe, due to flow deceleration, changes in sand-to-mud ratio, and the time required for development of cohesive bonds and the transition to a transitional flow regime, leading to increased deposition of Structured sandstone–mudstone distally.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"473 ","pages":"Article 106766"},"PeriodicalIF":2.7,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142658842","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}