Depositional Record最新文献

{"title":"The Marinoan cap carbonate of Svalbard: Syngenetic marine dolomite with 17O-anomalous carbonate-associated sulphate","authors":"Ian J. Fairchild,&nbsp;Huiming Bao,&nbsp;Richard J. Windmill,&nbsp;Ian Boomer","doi":"10.1002/dep2.201","DOIUrl":"10.1002/dep2.201","url":null,"abstract":"<p>Two cap carbonates overlying Cryogenian panglacial deposits are found in North-East Svalbard of which the younger (635 Ma) forms the base of the Ediacaran Period. It is represented by a transgressive succession in which laminated dolostone, typically around 20 m thick (Member D1), is succeeded transitionally by a similar thickness of impure carbonates (Member D2). In Spitsbergen, there is evidence of microbially influenced sediment stabilisation and carbonate precipitation in the lower part of D1, whilst the upper part of D1 and D2 show centimetre-decimetre-scale graded units with undulatory lamination interpreted as evidence of storm activity. Carbonate originated as possible freshwater whitings, as well as microbial precipitates. Exhumed and eroded hardgrounds display replacive 10–30 μm dolomite crystals with cathodoluminescence characteristics consistent with early diagenetic manganese and iron reduction. Regionally, carbon isotope values consistently decrease by around 2‰ from around −3‰ over 30 m of section which is both a temporal and a bathymetric signal, but not a global one. An exponential decline in carbonate production predicted by box models is fitted by a semi-quantitative sedimentation model. A mass-anomalous ¹⁷O depletion in carbonate-associated sulphate in dolomite, inherited from precursor calcite, decreases from −0.6 to −0.3‰ in the basal 15 m of section and then approaches background values. The post-glacial anomalous ¹⁷O depletion in carbonate-associated sulphate and barite elsewhere has been interpreted in terms of ultra-high pCO₂ at the onset of deglaciation. Such anomalies, with larger amplitude, have been reported in Svalbard from underlying lacustrine and tufaceous limestones representing a hyperarid glacial environment. The anomalous sulphate could be produced contemporarily, or the internally drained landscape may have continued to release ¹⁷O-anomalous sulphate as it was transgressed during cap carbonate deposition. The late Cryogenian to earliest Ediacaran record in Svalbard provides the most complete record of the basal ¹⁷O-depletion event in the world.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2022-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.201","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49089993","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Microbial EPS-mediated amorphous calcium carbonate–monohydrocalcite–calcite transformations during early tufa deposition","authors":"Paul L. Broughton","doi":"10.1002/dep2.200","DOIUrl":"10.1002/dep2.200","url":null,"abstract":"<p>The Holocene Wolfenden tufa deposit in south-eastern British Columbia, western Canada, preserves a unique record of the earliest stages of calcium carbonate deposition resulting from microbial extracellular polymeric substances-mediated precipitation of amorphous calcium carbonate (ACC) with partial transformation to monohydrocalcite (MHC) and subsequently to nanocrystalline calcite. This is the first documentation of tufa mineralogy involving ACC transformation to MHC. Progressive dehydration triggered ACC–MHC–nanocrystalline calcite transformations on bryophytes, algae and cyanobacteria sheaths. The adsorption of extracellular polymeric substances matrix molecules into the ACC and ACC–MHC structures preserved polymorph mineralogy of incomplete transformation. Unusual concentrations of biofilm extracellular polymeric substances filaments provided nucleation sites for the ACC precipitation. The ACC nucleation calcified extracellular polymeric substances filaments and resulted in partially coalesced arrays of nanoscale ACC spheroids. Mesocrystalline structures of MHC reconfigured the concentric growth layers of ACC precipitate with bulbous ACC–MHC protuberances. Nanocrystalline rhombic faces of calcite developed within and on the surfaces of the ACC–MHC protuberances. Dehydration of these concentric growth layers of ACC–MHC resulted in the transformation into nanocrystalline calcite with substrates coalesced into micrite fabrics. Recrystallisation obliterated evidence of the calcified extracellular polymeric substances filaments and resulted in microcrystalline calcite spar domains as the widespread encrustation fabric. Localised magnesium adsorption during nucleation of the ACC within the biofilms resulted in needle calcite crystals without the precursor ACC–MHC transformation process. Microbial extracellular polymeric substances-mediated precipitation of ACC as a necessarily critical step in the earliest phase of the tufa deposition process, leading to the nucleation of calcite has been underappreciated and generally not considered. These earliest stages of calcium carbonate precipitation are proposed as a possible template for other tufa deposits, where the evidence of microbial extracellular polymeric substances-mediated precipitation of ACC with transformation to MHC and subsequently to nanocrystalline calcite has been obscured by recrystallisation into micrite and spar fabrics.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2022-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.200","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43413488","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Petrographic and geochemical constraints on the formation of gravity-defying speleothems","authors":"Adrian Immenhauser,&nbsp;Rene Hoffmann,&nbsp;Sylvia Riechelmann,&nbsp;Mathias Mueller,&nbsp;Dennis Scholz,&nbsp;Stefan Voigt,&nbsp;Stefan Niggemann,&nbsp;Dieter Buhl,&nbsp;Maximilian Dornseif,&nbsp;Alexander Platte","doi":"10.1002/dep2.199","DOIUrl":"10.1002/dep2.199","url":null,"abstract":"<p>Cave carbonates, seemingly growing in defiance of gravity, have attracted the community's interest for more than a century. This paper focusses on ‘helictites’, contorted vermiform speleothems with central capillaries. Petrographic, crystallographic and geochemical data of calcitic and aragonitic helictites (recent to 347 ka) from three caves in Western Germany are placed in context with previous work. Aragonitic helictites from one site, the Windloch Cave, form exceptionally large and complex structures that share similarities with the celebrated helictite arrays in the Asperge Cave in France. Aragonitic and calcitic helictites differ significantly in their crystal fabrics and internal geometry. Calcitic helictites are best described as a composite crystal fabric consisting of fibrous mesocrystals. Aragonite helictites display a complex fabric of acicular to platy crystals, some of which show evidence for growth-twinning and perhaps crystallisation via a monoclinal precursor stage. The micro-tomographic characterisation of several orders of channels and their complex architecture raises important questions regarding fluid migration and helictite architecture. In terms of their isotope geochemistry, helictites are depleted in ¹³C to various degrees, isotope values that are controlled by the mixing of fluids and mineralogy-related fractionation. Regarding their δ¹⁸O values, most helictites overlap with other calcitic and aragonitic speleothems. Previous models explaining the twisted morphology of helictites are discussed from the viewpoint of fluid migration and CO₂ degassing rates, mineralogy and helictite petrography. For the complex aragonitic helicities documented here, the most likely mechanisms to explain the contorted growth forms include the internal capillary network combined with localised (sector) growth at the helictite tip. The morphologically simpler calcitic helictites are best explained by capillary and surface flow. Future work should include geomicrobiology to assess the significance of induced mineralisation and transmission electron microscopy analysis to more quantitatively assign crystallographic properties.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2022-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.199","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49264904","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Pioneer species of Cyanobacteria in hot springs and their role to travertine formation: The case of Aedipsos hot springs, Euboea (Evia), Greece","authors":"Christos Kanellopoulos,&nbsp;Vasiliki Lamprinou,&nbsp;Artemis Politi,&nbsp;Panagiotis Voudouris,&nbsp;Athena Economou-Amilli","doi":"10.1002/dep2.198","DOIUrl":"10.1002/dep2.198","url":null,"abstract":"<p>Cyanobacteria are considered to be among the first microorganisms to settle in hot springs where they form a favourable environment for further biological establishment. Nevertheless, the exact pioneer species and how early they start participating in the biomineralisation processes remain unknown. The aim of the present study was twofold, that is, to identify the pioneer Cyanobacteria in hot springs (i.e. Aedipsos area, Greece) and to record their early biomineralisation processes. The in situ experimental approach included the setup of sterile glass and/or plexiglass slides in several locations to facilitate colonisation by Cyanobacteria, and removal of slides for study after 48–202 h. Synechococcales (37%) and Oscillatoriales (33%) were the dominant orders, followed by Chroococcales (15%) and Spirulinales (11%); whereas Chroococcidiopsidales (4%) was found only in a few sites. The order Nostocales was not observed at the early stages of colonisation although it was present in mature stages. Forty-three species of Cyanobacteria were identified as pioneer microorganisms, with <i>Spirulina subtilissima</i> being the most frequently found. The most common pioneers were multicellular filamentous Cyanobacteria, that is, organisms with a large surface area able to form significant amounts of extracellular polymeric substances. Among the pioneers, thermophilic species of Cyanobacteria were typical such as <i>Chroococcidiopsis thermalis</i>, <i>Chroococcus thermalis</i>, <i>Leptolyngbya thermalis</i>, <i>S. subtilissima</i> and <i>Symploca thermalis</i>, as well as typical limestone substrate species such as <i>Chroococcus lithophilus</i> and <i>Leptolyngbya laminosa</i>. Temperature seems to affect biodiversity. Also, pioneers were found to contribute to the biomineralisation processes from their first appearance. In the studied samples, three biomineralisation processes were identified, that is, (i) calcification of cyanobacterial sheaths, (ii) trapping of carbonate crystals on a crystal retention lattice formed by extracellular polymeric substances and filaments and (iii) trapping and confinement of carbonate crystals around filamentous Cyanobacteria.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2022-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.198","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43308687","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Neogene history of fluvial to shallow marine successions in the Kendari Basin, SE Sulawesi, Indonesia","authors":"Abang Mansyursyah Surya Nugraha,&nbsp;Robert Hall,&nbsp;Marcelle BouDagher-Fadel,&nbsp;Jonathan A. Todd,&nbsp;Adam D. Switzer","doi":"10.1002/dep2.196","DOIUrl":"https://doi.org/10.1002/dep2.196","url":null,"abstract":"<p>Collision between Australia and SE Asia began in Sulawesi, the world's eleventh-largest island, in the Early Miocene and subsequently Neogene sediments were deposited largely in coastal to shelf environments throughout the island. These sediments have been assigned to the Celebes Molasse, previously considered as a single post-orogenic unit deposited unconformably on pre-Neogene sedimentary, metamorphic and ophiolitic rocks. The most complete and extensive sequences of Neogene sediments are in the Kendari Basin, situated at the southern end of the SE Arm of Sulawesi, where an outcrop-based sedimentological study was undertaken to interpret depositional environments, palaeogeography and stratigraphy. The oldest Neogene sediments are shallow marine carbonates and deltaic siliciclastics of the Bungku Formation. They are unconformably overlain by the Upper Miocene Pandua Formation which consists of sediments deposited in a variety of environments including braided river channels, fluvio-tidal channels, tidal flats, mouth bar complex and shoreface deposits. A Mio-Pliocene subaerial unconformity separates the marginal marine serpentinite-rich sediments of the Pandua Formation from the overlying fluviatile quartz-rich Langkowala Formation. The sediments of the lower part of the Langkowala Formation include conglomeratic channel fill, while the sediments of the upper part are transgressive deposits decreasing in maximum grain-size, marked by a reduction in channel/overbank ratio and increasing tidal influence. The transgressive Pliocene Eemoiko Formation is characterised by transgressive lags or onlap shell beds and deposits of a landwards-backstepping carbonate platform. The improved understanding of the Kendari Basin will aid the interpretation of the sedimentation history of frontier basins surrounding SE Sulawesi, many of which have not yet been drilled.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2022-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.196","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50155328","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Neogene history of fluvial to shallow marine successions in the Kendari Basin, SE Sulawesi, Indonesia","authors":"A. M. S. Nugraha, R. Hall, M. BouDagher-Fadel, J. Todd, A. Switzer","doi":"10.1002/dep2.196","DOIUrl":"https://doi.org/10.1002/dep2.196","url":null,"abstract":"Collision between Australia and SE Asia began in Sulawesi, the world's eleventh‐largest island, in the Early Miocene and subsequently Neogene sediments were deposited largely in coastal to shelf environments throughout the island. These sediments have been assigned to the Celebes Molasse, previously considered as a single post‐orogenic unit deposited unconformably on pre‐Neogene sedimentary, metamorphic and ophiolitic rocks. The most complete and extensive sequences of Neogene sediments are in the Kendari Basin, situated at the southern end of the SE Arm of Sulawesi, where an outcrop‐based sedimentological study was undertaken to interpret depositional environments, palaeogeography and stratigraphy. The oldest Neogene sediments are shallow marine carbonates and deltaic siliciclastics of the Bungku Formation. They are unconformably overlain by the Upper Miocene Pandua Formation which consists of sediments deposited in a variety of environments including braided river channels, fluvio‐tidal channels, tidal flats, mouth bar complex and shoreface deposits. A Mio‐Pliocene subaerial unconformity separates the marginal marine serpentinite‐rich sediments of the Pandua Formation from the overlying fluviatile quartz‐rich Langkowala Formation. The sediments of the lower part of the Langkowala Formation include conglomeratic channel fill, while the sediments of the upper part are transgressive deposits decreasing in maximum grain‐size, marked by a reduction in channel/overbank ratio and increasing tidal influence. The transgressive Pliocene Eemoiko Formation is characterised by transgressive lags or onlap shell beds and deposits of a landwards‐backstepping carbonate platform. The improved understanding of the Kendari Basin will aid the interpretation of the sedimentation history of frontier basins surrounding SE Sulawesi, many of which have not yet been drilled.","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2022-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51502426","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Insights on the biomineralisation processes and related diversity of cyanobacterial microflora in thermogenic travertine deposits in Greek hot springs (North-West Euboea Island)","authors":"Christos Kanellopoulos,&nbsp;Vasiliki Lamprinou,&nbsp;Artemis Politi,&nbsp;Panagiotis Voudouris,&nbsp;Athena Economou-Amilli","doi":"10.1002/dep2.197","DOIUrl":"10.1002/dep2.197","url":null,"abstract":"<p>The aim of this study is to identify the biomineralisation processes in hot springs of North-West Euboea Island by assessing the physico-chemical parameters of the hot water, the travertine mineralogical composition and facies, and the cyanobacterial microflora. In the studied area, the main mineral phases are calcite and aragonite, creating laminated and shrub facies of travertine deposits in close association with the cyanobacterial microflora. Microscopic analysis of fresh and cultured field samples shows the presence of 81 taxa of Cyanobacteria belonging to six orders, that is, Oscillatoriales, Synechococcales, Spirulinales, Chroococcales, Nostocales and Chroococcidiopsidales with the main factors controlling biodiversity being temperature, salinity and access to sunlight. No Cyanobacteria species were identified in areas with temperatures over 65^oC. In areas with high salinity (27–37‰), the order Oscillatoriales predominates. On the other hand, in areas with high temperatures (63^oC), fewer orders were observed, usually only Synechococcales and Spirulinales. In areas with lower temperatures (37^oC), larger numbers of Cyanobacteria orders were identified. Additionally, salinity seems to regulate the presence of the Nostocales order. The combined geobiological study revealed the presence of four biomineralisation processes involving calcium carbonate minerals, that is, (i) filamentous Cyanobacteria and extracellular polymeric substances trapping calcium carbonate crystals, (ii) extracellular polymeric substances acting as a template favouring mineral precipitation for crystal nucleation, (iii) formation of calcified Cyanobacteria sheaths and (iv) alteration of calcium carbonate crystals by endolithic Cyanobacteria. The identified biomineralisation processes suggest that the formation of calcium carbonate crystals is due to the metabolic activity of Cyanobacteria, or that the Cyanobacteria favour the deposition or the alteration of already existing crystals. The combination of these processes and the non-biotic (abiotic) mineralisation result in the formation of hybrid carbonates in the study area.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2022-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.197","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45660408","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Sedimentologic and stratigraphic criteria to distinguish between basin-floor and slope mudstones: Implications for the delivery of mud to deep-water environments","authors":"Kévin Boulesteix,&nbsp;Miquel Poyatos-Moré,&nbsp;Stephen S. Flint,&nbsp;David M. Hodgson,&nbsp;Kevin T. Taylor,&nbsp;Rufus L. Brunt","doi":"10.1002/dep2.191","DOIUrl":"10.1002/dep2.191","url":null,"abstract":"<p>Deep-water mudstones overlying basin-floor and slope sandstone-prone deposits are often interpreted as hemipelagic drapes deposited during sand starvation periods. However, mud transport and depositional processes, and resulting facies and architecture of mudstones in deep-water environments, remain poorly understood. This study documents the sedimentology and stratigraphy of basin-floor and slope mudstones intercalated with sandstone-prone deposits of the Laingsburg depocentre (Karoo Basin, South Africa). Sedimentologic and stratigraphic criteria are presented here to distinguish between slope and basin-floor mudstones, which provide a tool to refine palaeogeographical reconstructions of other deep-water successions. Several mudstone units were mapped at outcrop for 2500 km² and investigated using macroscopic and microscopic core descriptions from two research boreholes. Basin-floor mudstones exhibit a repeated and predictable alternation of bedsets dominated by low-density turbidites, and massive packages dominated by debrites, with evidence of turbulent-to-laminar flow transformations. Slope mudstones exhibit a similar facies assemblage, but the proportion of low-density turbidites is higher, and no repeated or predictable facies organisation is recognised. The well-ordered and predictable facies organisation of basin-floor mudstones suggest local point sources from active slope conduits, responsible for deposition of compensationally stacked muddy lobes. The lack of predictable facies organisation in slope mudstones suggests deposition took place in a more variable range of sub-environments (i.e. ponded accommodation, minor gully/channel-fills, levees). However, regional mapping of three mudstone units evidence basinward tapering and similar thicknesses across depositional strike. This geometry is consistent with the distal part of basin margin clinothems, and suggests laterally extensive mud delivery across the shelf edge combined with along-margin transport processes. Therefore, the sedimentology and geometry of mudstones suggests that mud can be delivered to deep-water dominantly by sediment gravity flows through point source and distributed regionally, during periods of up-dip sand storage. These findings challenge the common attribution of deep-water mudstones to periods of basin-floor sediment starvation.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2022-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.191","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49201100","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Observed and modelled tidal bar sedimentology reveals preservation bias against mud in estuarine stratigraphy","authors":"Lisanne Braat,&nbsp;Harm Jan Pierik,&nbsp;Wout M. van Dijk,&nbsp;Wietse I. van de Lageweg,&nbsp;Muriel Z. M. Brückner,&nbsp;Bas van der Meulen,&nbsp;Maarten G. Kleinhans","doi":"10.1002/dep2.190","DOIUrl":"10.1002/dep2.190","url":null,"abstract":"Mud plays a pivotal role in estuarine ecology and morphology. However, field data on the lateral and vertical depositional record of mud are rare. Furthermore, numerical morphodynamic models often ignore mud due to long computational times and simplifications of mixed depositional processes. This study aims to understand the spatial distribution, formative conditions and preservation of mud deposits in the intertidal zone of bars in high‐energy sand‐dominated estuaries, and to elucidate the effects of mud on morphology, ecology and stratigraphic architecture. To meet these objectives, field data (historic bathymetry, bio‐morphological maps and sediment cores of the shoal of Walsoorden, Western Scheldt estuary, the Netherlands) were combined with complementary hydro‐morphodynamic numerical modelling (Delft3D). Based on the field observations, two types of mud deposits were distinguished: (1) mudflat deposits, which are thick (>10 cm) mud beds at the surface associated with high elevations and low accumulation rates; and (2) mud drapes, which are thin (millimetre to centimetre) buried laminae that form and preserve at a wide range of elevations and energy conditions. Model results show that deposition on mudflats occurs just after high‐tide slack water in areas shielded from high flood velocities, suggesting that mud accumulation is mostly controlled by elevation, flow velocity and flow direction. Mud accumulation increases shoal elevation, sometimes to supratidal levels. This reduces flow over the shoal, which in turn reduces chute channel formation, stabilises bar morphology and decreases local tidal prism. These effects further promote mud deposition and vegetation settling. Although observations show that mud cover at the surface is relatively high (20%–40% of the intertidal area), mud constitutes only a small percentage of the total estuary volume (ca 5%) revealing that only a small fraction is preserved in the stratigraphy. Due to this mismatch between surface and subsurface expression of mud, interpretations of estuarine stratigraphy risk underestimating the influence of mud at the surface on morphodynamics and habitats.","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2022-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.190","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41713978","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Channel trajectories control deep-water stratigraphic architecture","authors":"Paul D. Morris,&nbsp;Zoltán Sylvester,&nbsp;Jacob A. Covault,&nbsp;David Mohrig","doi":"10.1002/dep2.189","DOIUrl":"10.1002/dep2.189","url":null,"abstract":"<p>Interpretation of deep-water channel deposits is challenging because the spatial arrangement of their constituent lithologies is highly variable. This variability is often thought to be a signature of complex interactions between controlling boundary conditions and processes. A three-dimensional forward stratigraphic model of a sinuous meandering channel is used to explore the production of channelised deep-water stratigraphy. This model highlights three stages of stratigraphic evolution for channel belts: (1) an initial phase of rapid growth in mean belt width and variability in belt width driven by increasing channel sinuosity; (2) a subsequent phase of reduced belt-width growth rate because of cutoff processes; and (3) a mature phase during which repeated bend lifecycles act to produce a statistically stable channel-belt width. When a trajectory defining the vertical movement of a channel over time is added to the model, commonly recognised patterns of deep-water channel-belt stratigraphy are produced. These results demonstrate how forward stratigraphic models provide insights into processes governing the evolution of deep-water stratigraphy that elude interpretations of static outcrops and seismic images of subsurface examples.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2022-04-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.189","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41696222","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}