Sedimentary Geology最新文献

{"title":"Field observations on the characteristics of sand ripples on tidal flats","authors":"Chuang Jin ,&nbsp;Zheng Gong ,&nbsp;Ran Ge ,&nbsp;Xindi Chen","doi":"10.1016/j.sedgeo.2024.106714","DOIUrl":"10.1016/j.sedgeo.2024.106714","url":null,"abstract":"<div><p>Ripples on tidal flats significantly influence bedform roughness and near-bed turbulence, yet their dynamics in sandy and muddy environments remain incompletely understood. While laboratory studies have elucidated the effects of mud content and extracellular polymeric substances (EPSs) on ripple formation and stability, the interactions between ripple characteristics, EPS, and mud content in natural settings are more complex and not thoroughly explored. To address this gap, we conducted field studies on sand ripples at the central Jiangsu coast, China, using high-resolution drone photogrammetry to accurately measure ripple dimensions. We performed bedload sampling at both ripple crests and troughs to analyze median grain size, mud content, and EPS concentrations. Our results show that the investigated ripple wavelengths range from 34 to 46 mm, and heights vary between 2.7 and 5.3 mm. Ripples developed near tidal creeks show pronounced asymmetry. Significantly, EPS concentrations are markedly higher at the ripple crests than at the troughs, and it follows a power-law relationship with the median grain size. These results highlight the complex intricate relationship between the ripple morphology, environmental forcing conditions, and EPS content. Our findings enrich the understanding of ripple development and the factors influencing current-dominated ripples in natural environments. This research also adds to the better prediction of the bedform roughness and quantification of the near bed sediment transport.</p></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"470 ","pages":"Article 106714"},"PeriodicalIF":2.7,"publicationDate":"2024-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141713812","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":"Formation of the crust on the surface of cold-climate aeolian quartz grains – A nano-scale study","authors":"Barbara Woronko ,&nbsp;Martyna E. Górska ,&nbsp;Richard Wirth ,&nbsp;Anja Schreiber ,&nbsp;Krzysztof Kulikowski ,&nbsp;Georg Schwamborn","doi":"10.1016/j.sedgeo.2024.106715","DOIUrl":"10.1016/j.sedgeo.2024.106715","url":null,"abstract":"<div><p>Sand-sized quartz grains selected from sediments of a Pleistocene inland dune (eastern Poland) were subjected to a series of laboratory analyses, including grain-size distribution, morphoscopy analysis, microtextural analysis using scanning electron microscope (SEM) and nanostructural analysis using transmission electron microscope (TEM). The results indicate the presence of a crust on the surface of all of the studied quartz grains and a surprisingly low number of aeolian-induced mechanical microtextures. The TEM examination identifies illite-smectite assemblages as the main component of the crust, accompanied by amorphous silica, local accumulation of Fe, K, Ca, Mg oxides, and mineral particles (quartz, K-feldspar, chlorite). The thickness of the crust reaches approx. 0.1–0.2 μm and varies from the minimum on micro-protrusions up to the maximum in micro-cavities. Here, we present a new theory on the origin of the crust observed on the surface of cold-climate aeolian quartz grains. We postulate that the crust is formed within a near-surface saltation layer during active aeolian transport of sand-sized grains and clay-sized particles operating under cold-climate conditions. The development of abrasion features and the formation of the crust are interpreted here to occur simultaneously and continuously during the aeolian transport. The formation of the crust results from specific properties of aeolian transport (i.e. self-induced electrification and electrification mechanisms of quartz grains) and the quartz grains themselves (i.e. grain shape and surface microtopography).</p></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"470 ","pages":"Article 106715"},"PeriodicalIF":2.7,"publicationDate":"2024-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141622659","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":"Firmgrounds and hardgrounds in the Coniacian carbonate platform of the Iberian basin: Origin and model for development of omission surfaces in tidal environments","authors":"José F. García-Hidalgo,&nbsp;Javier Gil-Gil","doi":"10.1016/j.sedgeo.2024.106713","DOIUrl":"https://doi.org/10.1016/j.sedgeo.2024.106713","url":null,"abstract":"<div><p>Distinctive erosional and omission surfaces occur at several stratigraphic levels in the tidal carbonates of the 3rd-order Coniacian sequence (Iberian Basin). They are ancient analogs of omission surfaces developed on lithified carbonates in subaerial and coastal settings. Omission surfaces consist of (i) firmground <em>Glossifungites</em> ichnofacies (<em>Balanoglossites</em>-<em>Thalassinoides</em>); and (ii) hardground <em>Trypanites</em> ichnofacies (scalloped and planar surfaces and <em>Gastrochaenolites</em>-<em>Entobia</em> surfaces). Firmgrounds are also related to erosion or ferruginous crusts. Hardground surfaces are related to bioerosion, dissolution and physical erosion. Grain size and textural features in <em>Balanoglossites</em> and <em>Thalassinoides</em> firmground surfaces are essentially the same, suggesting that even bathymetry could be similar. Several stages in hardgrounds consist of different, scalloped or planar surfaces related to bioerosion, dissolution and physical erosion. <em>Gastrochaenolites</em>-<em>Entobia</em> borers represent a major change in the trace fossil associations and imply different processes in their origin, being originated at slightly different depths with <em>Gastrochaenolites</em> representing shallower environments. The studied field sections display a cyclicity on the scale of meters that tentatively reflects the presence of 4th-order parasequence sets. Two kinds of sedimentary discontinuities have been used for correlation: omission surfaces and ferruginous crusts representing regional sea level falls and rises. Part of the described surfaces does not appear to have been previously recognized in older carbonate deposits. Their common presence of similar surfaces along modern coasts and in karst terrains, as well as their abundance in the Coniacian sequence, suggests that they might also be abundant in the geologic record in other sedimentary basins for defining palaeoshorelines.</p></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"470 ","pages":"Article 106713"},"PeriodicalIF":2.7,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0037073824001362/pdfft?md5=1993101c8cf4af9f4491127bb043c7e8&pid=1-s2.0-S0037073824001362-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141607193","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":"Statistical analysis of the Hurst index indicating sedimentary processes' evolution trend in the deep lacustrine mudrock sequences: A case study of the Jiyang Depression, Bohai Bay Basin, eastern China","authors":"Yueyun Wang ,&nbsp;Zhuang Ruan ,&nbsp;Bingsong Yu ,&nbsp;Zhenhuan Shen","doi":"10.1016/j.sedgeo.2024.106712","DOIUrl":"10.1016/j.sedgeo.2024.106712","url":null,"abstract":"<div><p>Quantitative identification of sedimentary processes' evolution trend has substantially influenced the exploration of lacustrine mudrocks. To explore the indicative applicability of the Hurst index (HI) for analyzing the sedimentary processes' evolution trend in a deep lacustrine sequence, lacustrine mudrocks from wells L69, FY1, and NY1 in the Jiyang Depression, eastern China are selected. The comparable fourth-order cycle is divided through lithofacies observation, total organic carbon (TOC), and natural gamma ray (GR) logs combined with previous studies. In addition, the variation of accommodation space is selected to represent the sedimentary processes' evolution trend in the lacustrine environment, characterized by the frequency of oscillation (FST) and directionality (D). Further, HI is introduced to identify the long-term persistence of the sedimentary processes' evolution trend in the lacustrine environment. Through the criteria for the series selections, the TOC series and GR logs passed the Hurst phenomenon test, and the computed HI of those two series was selected to evaluate its effectiveness toward the lacustrine sedimentary processes' evolution trend. The HI computed from the TOC series demonstrates strong negative linear relationships with FST and D, with R² in 0.833 and 0.814, respectively. Besides, the HI from the more accessible GR logs demonstrates robust negative linear relationships with FST and D, with R² in 0.981 and 0.976, respectively. The statistical analysis indicates that the content of deep lake subfacies, shale, and mudstone could affect the long-term persistence of the lacustrine mudrock sequence. Thus, the HI could be an alternative indicator to identify the imperceptible sedimentary processes' evolution trend in the deep lacustrine environment.</p></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"470 ","pages":"Article 106712"},"PeriodicalIF":2.7,"publicationDate":"2024-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141572483","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":"Dolomite occurrence within drift deposits, Maldives archipelago","authors":"","doi":"10.1016/j.sedgeo.2024.106711","DOIUrl":"10.1016/j.sedgeo.2024.106711","url":null,"abstract":"<div><p>Considerable attention has been dedicated to the sedimentological processes associated with carbonate drift and contourite deposits, but a noticeable gap exists in the understanding of the diagenetic aspects of those deposits, especially dolomitization. This study presents an examination of dolomites from Middle to Late Miocene drift deposits collected during IODP Expedition 359 to the Maldives archipelago. Multiple geochemical parameters and petrographic analysis are used to explore the potential role of closed versus open system dolomitization in the two oldest drift sequences, which are overlain by a multimillion year-long hiatus. Overall, dolomite abundance is variable, but 50 % to nearly 100 % in a 30 m thick interval below the unconformity surface at one of the examined sites. The dolomite in the study interval consists of very fine-to-fine-sized crystalline dolomite cements and mimetically replaced dolomite grains. All dolomite is non-stoichiometric (mean 42.7 ± 2.0 mol% MgCO₃) and mostly poorly ordered. Geochemical attributes include relatively invariant δ¹³C (+1.3 ‰ to +1.7 ‰ VPDB) and relatively high Sr concentrations in dolomite cements (mean 505 ppm) and dolomitized grains (mean 784 ppm). δ¹⁸O values and the constraints of burial histories indicate dolomitization in normal marine seawater at burial depths of 0 to 300 m and temperatures of ∼10 °C–14 °C below an ocean water column 100 to 400 m deep. Sr-isotope ages suggest dolomitization of the most extensively dolomitized interval below the unconformity occurred between 12.3 Ma and 6.7 Ma. Overall, the geochemical data and previously published δ³⁴S_CAS data suggest a closed, diffusion-dominated system created most of the dolomite. However, the youngest dolomite's age and bulk rock Sr isotope ages of calcitic rocks at the base of the drift deposits can only be explained by the advective flux of seawater through all the drift deposits. Furthermore, the geological context, including permeable facies, ocean current patterns, and other indicators, such as the absence of hardground or permeability barriers, suggests that some open system dolomitization may have also occurred.</p></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"470 ","pages":"Article 106711"},"PeriodicalIF":2.7,"publicationDate":"2024-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141572384","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":"Geochemistry characterization of diagenesis from Mishrif reservoir rocks in the Central Mesopotamian Basin, Iraq: Implication for the differential diagenesis and petroleum significance","authors":"Huan Wang ,&nbsp;Lirong Dou ,&nbsp;Xingyang Zhang ,&nbsp;Jiquan Yin ,&nbsp;Beiwei Luo ,&nbsp;Anjiang Shen ,&nbsp;Yu Ji ,&nbsp;Yifan Song","doi":"10.1016/j.sedgeo.2024.106710","DOIUrl":"10.1016/j.sedgeo.2024.106710","url":null,"abstract":"&lt;div&gt;&lt;p&gt;The Cenomanian Mishrif Formation is one of the most important carbonate reservoirs in the Mesopotamian Basin. Detailed petrographic analysis, aided by geochemistry and burial history establishment on Mishrif carbonates from the AD oilfield, located at the margins of the Central Mesopotamian Basin of Iraq, presents a distinctive differential diagenetic mechanism that significantly impacts reservoir quality and exhibits a pronounced relationship with tectonic evolution and hydrocarbon accumulation. Analyses of petrographic features, carbon‑oxygen isotopes, and minor and rare-earth elements reveal that echinoderm shells and rim calcites are results of marine waters; sparry calcites, matrix, and vein calcites from host rock primarily precipitate from meteoric fluid; microspars and vein calcites in the concretionary limestone are derived from brine water. The development of concretionary limestone mainly involves a complex process that comprises extensive bioturbation in marine waters, substantial fabric-selective dissolution in the meteoric zone, and significant sparry calcites occluded dissolved spaces in shallow burial environments. Winding and skew seams of argillaceous sediment around concretionary limestones, as well as the excellent preservation of skeletal remains inside the concretionary zone, manifest that the development of the concretionary limestone accomplished during the early diagenesis stage and pre-compaction. These centimeter-to-decimeter scaled concretionary limestones intermixed with host rock holding abundant open porosities shape the Mishrif reservoir and result in an inconspicuous, dual permeability system. The burial history, integrated with the diagenetic sequence and tectonic evolution, elucidates four stages that clarify interactions of diagenesis, porosity preservation, and hydrocarbon accumulation. The Cenomanian to Turonian period was a critical stage for the development of effective reservoir capacity. The end of the Cretaceous, marked by the contraction of the Neo-Tethys and the complete closure of the South Neo-Tethys, witnessed an early hydrocarbon accumulation event that enhanced reservoir porosity preservation. During the Paleocene to the Early Miocene epoch, the Neo-Tethys tended to be closing. As a result, the Mishrif Formation experienced shallow burial and generated typical concretionary limestone, which provided a rigid framework against compaction. From the Early Miocene to the present, the total closure of the Neo-Tethys and the Zagros Orogeny initiated a significant late oil-filling event that acted as the main accumulation moment, coinciding with efficient trap development and other optimal petroleum conditions. This study contributes to (1) comprehending the genesis of the differential diagenesis and its effect on pore structures and reservoir heterogeneity, and (2) linking diagenetic sequence to tectonic evolution and hydrocarbon accumulation of foreland basins evolved from Neo-Tethys tectonics.&lt;","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"470 ","pages":"Article 106710"},"PeriodicalIF":2.7,"publicationDate":"2024-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141503809","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":"Sediment colour as a marker of syn-depositional and early diagenetic processes in glaciofluvial sediments","authors":"Daniel Šimíček ,&nbsp;Ondřej Bábek ,&nbsp;Hedvika Weinerová ,&nbsp;Lukáš Ackerman ,&nbsp;Jaroslav Kapusta ,&nbsp;Tomáš Magna","doi":"10.1016/j.sedgeo.2024.106703","DOIUrl":"10.1016/j.sedgeo.2024.106703","url":null,"abstract":"<div><p>The continental red beds, encompassing a broad spectrum of genetic types, can serve as important palaeoclimatological and palaeoenvironmental archives. The origin of sediment colouration is a complex process involving abiotic processes (e.g., breakdown of original and precipitation of newly-formed minerals), which, together with biogenic factors, lead to mobilisation of redox-sensitive elements and precipitation of Fe- and Mn-(oxy)hydroxides. There is still discussion about the interpretation of the continental red beds as palaeoclimatological archives or the colour patterns reflecting ancient redox gradients. The layers coloured in red, yellow or black can be found in the Quaternary glaciofluvial sediments in the Czech Republic. We are using a combination of field study with multi-spectral petrophysical, petrological and geochemical analyses to investigate the mechanism and timing of the origin of coloured coatings in glaciofluvial sediments, and causes of cycling of Fe, Mn, and other redox sensitive elements and isotopes. The results show that both syn-depositional and early diagenetic processes are responsible for the origin of colour patterns in the Quaternary glaciofluvial sediments. The stable molybdenum and iron isotope fractionation is primarily driven by the breakdown of the primary Fe and Mn-bearing silicates and the precipitation of the secondary Fe- and Mn-(oxy)hydroxides, such as goethite and birnessite. These precipitates are the main components of colouring coatings on the detrital grains and are able to bind other redox-sensitive elements, such as Cu, As, Mo, U, and REEs. The textural patterns and geochemistry suggest that the colour features were developed in the time range of decades to several thousand years after the deposition along ancient subsurface redox gradients due to changes in groundwater flow associated with primary lithology, glaciotectonics, and seasonal changes in the active layer of permafrost. The coatings show morphological features (rods, botryoids) and geochemical signatures (e.g., increased P contents) suggesting involvement of microorganisms to their precipitation.</p></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"470 ","pages":"Article 106703"},"PeriodicalIF":2.7,"publicationDate":"2024-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141399520","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":"Diagenetic variability in Tertiary, syn-rift mixed siliciclastic‑carbonate depositional system (Lower Musayr Formation), Red Sea, Saudi Arabia","authors":"Arif Hussain ,&nbsp;Abdulwahab Bello ,&nbsp;Muhammad Naveed Butt ,&nbsp;Muhammad Hammad Malik ,&nbsp;Ardiansyah Koeshidayatullah ,&nbsp;Abduljamiu Amao ,&nbsp;Cornel Olariu ,&nbsp;Khalid Al-Ramadan","doi":"10.1016/j.sedgeo.2024.106699","DOIUrl":"10.1016/j.sedgeo.2024.106699","url":null,"abstract":"<div><p>Mixed siliciclastic‑carbonate depositional systems are prone to differential diagenesis due to lithological heterogeneity. However, unlike pure carbonate and/or siliciclastic counterparts, the diagenesis within mixed clastic‑carbonate successions remains poorly known. This study integrates sedimentological and petrographic analysis with porosity-permeability measurements to understand diagenetic variability and its impact on fluid flow in the Oligocene-Miocene mixed clastic‑carbonate system (lower part of Musayr Fm) in Midyan Basin, Red Sea, Saudi Arabia. Sedimentological observations highlight that siliciclastic intervals comprise conglomerates, coarse- to fine-grained sandstones and subordinate mudstones whereas mixed siliciclastic‑carbonate intervals are composed of shell, ooids and microbialites-dominated facies. Petrographic analysis indicates presence of several diagenetic processes in siliciclastic intervals including dissolution of unstable silicate grains (feldspar), formation of pore filling and/or grain-replacive kaolinite, precipitation of calcite and/or dolomite, and replacement of dolomite by silica. The siliciclastic strata exhibit minimal compaction fabrics with no stylolites and are characterized by higher permeability (average = 1884 md) and porosity (average = 18.7 %). On the other hand, mixed siliciclastic‑carbonate intervals underwent micritization, sparry calcite formation, dolomitization of micrite and bioclasts, and replacement of sparry calcite by pyrite and Fe-oxides. Wavy stylolite seams were also observed in ooid facies reflecting moderate chemical compaction. In addition, the porosity (average = 6.6 %) and permeability (average = 93 md) are magnitudes lower than siliciclastic counterparts. Significant differences between porosity and permeability of siliciclastic and mixed intervals are partly linked to relatively intense diagenetic alteration (higher cementation and chemical compaction) in mixed units. Understanding such diagenetic heterogeneity in mixed systems has important implications for identification of reservoir and non-reservoir zones and may provide useful insights for hydrocarbon exploration and carbon sequestration in the analogous strata in the subsurface.</p></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"470 ","pages":"Article 106699"},"PeriodicalIF":2.7,"publicationDate":"2024-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141395417","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":"Origin and significance of macroscopic organic aggregates from the lacustrine Aptian Crato Konservat-Lagerstätte","authors":"Filipe Giovanini Varejão ,&nbsp;Lucas Veríssimo Warren ,&nbsp;Mariza Gomes Rodrigues ,&nbsp;Mario Luis Assine ,&nbsp;Marcello Guimarães Simões","doi":"10.1016/j.sedgeo.2024.106692","DOIUrl":"10.1016/j.sedgeo.2024.106692","url":null,"abstract":"<div><p>The Crato <em>Konservat-Lagerstätte</em> is one of the main Mesozoic fossil sites from Gondwana, recording a wide diversity of terrestrial and non-marine aquatic fossils of great paleobiological and evolutionary significance. This conservation deposit is recorded in a 9 m-thick interval of laminite, microbialite, and grainstone deposited in a lake system with variable water level, alternating moments of hypersaline and freshwater conditions. Despite numerous studies describing new species of plants, arthropods, fish, pterosaurs, birds, and many others, there remains a significant gap in our understanding of the most common and archetypal fossils, which are the rod-shaped macrofossils found on bedding surfaces in distinct stratigraphic intervals of the Crato <em>Konservat-Lagerstätte</em>. The rod-shaped macrofossils are up to 1.6 cm-long and 0.1 cm-wide, straight to curved compressions that preserve pyritized microfossils. Here we interpret the rod-shaped macrofossils as macroscopic organic aggregates that sank into the lakebed in a process called lake snow. During high organic productivity periods in the epilimnion, planktonic organisms thrived and produced exopolymers responsible for aggregation. Their concentrations in the limestone bedding planes reflect intensity of lake snow and environmental seasonality. Aggregates are prolate particles that are commonly oriented, suggesting their transport as bedload for short distances, which was facilitated by biostabilization by microbes and their exopolymers. Finally, pyritization was mediated by microbial communities living in the lakebed.</p></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"470 ","pages":"Article 106692"},"PeriodicalIF":2.7,"publicationDate":"2024-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141398489","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":"Provenance response to evolving palaeogeography recorded by Carboniferous sandstones in the northern Pennine Basin, UK","authors":"A.C. Morton ,&nbsp;J.I. Chisholm ,&nbsp;D. Frei","doi":"10.1016/j.sedgeo.2024.106691","DOIUrl":"10.1016/j.sedgeo.2024.106691","url":null,"abstract":"<div><p>On the basis of a combination of heavy mineral data, provenance-sensitive heavy mineral indices, garnet major element chemistry, rutile trace element chemistry and zircon U–Pb geochronology, six major changes in sandstone provenance during Carboniferous deposition in the northern Pennine Basin, UK, have been recognised. These changes are a manifestation of both tectonic and climatic factors. The earliest Tournaisian sediment was supplied from the local Southern Uplands High, but the increasingly humid climate led to the establishment of the Pennine River system, which introduced northerly-derived sediment from farther afield in the mid Tournaisian. This system was operative until the mid Bolsovian, but shows stratigraphic variations due to changes in input from different parts of the Pennine River hinterland (East Greenland, northern Scotland, western Norway). These variations are believed to be at least partly related to tectonism, since the maximum supply from high-grade metamorphic sources in East Greenland in the Namurian was concurrent with a tectonically-driven change in drainage direction in this part of the northern sourcelands. In addition, at the base of the Visean, there was a temporary influx of mature sediment coincident with a climatically-driven regression and, at the base of the Duckmantian, sediment was briefly introduced from the west as a far-field manifestation of Alleghanian tectonism. Finally, continued uplift of the Variscan mountain belt to the south of the UK led to establishment of northward-directed transport systems that reached the northern Pennine Basin in the mid-Bolsovian, leading totermination of supply from the Pennine River.</p></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"470 ","pages":"Article 106691"},"PeriodicalIF":2.7,"publicationDate":"2024-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0037073824001143/pdfft?md5=33704eac263ed3ff25bede25463e2bd4&pid=1-s2.0-S0037073824001143-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141412552","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}