Journal of Sedimentary Research最新文献

{"title":"Stratigraphic analysis of XES02: Implications for the sequence stratigraphic paradigm","authors":"B. Prather, O. Falivene, P. Burgess","doi":"10.2110/jsr.2022.008","DOIUrl":"https://doi.org/10.2110/jsr.2022.008","url":null,"abstract":"\u0000 Sequence stratigraphy has the potential to provide a consistent method for integrating data, correlating strata, defining stratigraphic evolution, and generating quantifiable predictions. However, the consistent application requires a precise definition of concepts, stratigraphic units, bounding surfaces, and workflow. Currently no single generally accepted approach to sequence stratigraphic analysis exists, nor are there any robust tests of models and methods. Applying conventional sequence stratigraphic analysis to strata from an analog laboratory experiment (eXperimental EarthScape02, XES02) with known boundary conditions and chronology provides some initial robust testing of the models and methods. Despite stratigraphic architectures apparently consistent with those expected within the sequence stratigraphic paradigm, blind-test applications yield: 1) deducted erroneous base-level curves, 2) systems-tract classification mismatches, 3) disconnected systems-tracts type and actual base level, 4) time-transgressive basin-floor fans, and 5) missing systems tracts. Stratigraphic forward models using base-level curves derived from Wheeler diagrams cannot match the timing, redeposited-sediment volume, and depositional environments observed in the XES02 experiment. These mismatches result from common Wheeler diagram construction practice, producing poorly resolved base-level minima timing and base-level fall durations, hence inaccurate fall rates. Consequently, reconstructions of controlling factors based on stratal architectures remain uncertain, making predictions similarly uncertain. A reasonable path forward is to properly acknowledge these uncertainties while performing stratigraphic analysis and to address them through multiple scenario analysis and modeling.","PeriodicalId":17044,"journal":{"name":"Journal of Sedimentary Research","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2022-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42048324","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Demarcation of Early Pennsylvanian paleovalleys in depozones of the Appalachian foreland-basin system based on detrital-zircon U-Pb and Hf analysis","authors":"I. Allred, Mike J. Blum","doi":"10.2110/jsr.2021.128","DOIUrl":"https://doi.org/10.2110/jsr.2021.128","url":null,"abstract":"\u0000 Detrital-zircon (DZ) U-Pb data show that Appalachian-affiliated sediment was transported to western Laurentia by the Carboniferous, yet additional DZ U-Pb data from the eastern United States suggest that sediment-routing systems were oriented south toward the Ouachita deepwater sink. Within this context, this study presents DZ U-Pb ages from the Lower Pennsylvanian Caseyville Formation of Illinois, and U-Pb ages and εHf values from the coeval Pottsville Formation of Alabama as well as sandstone petrographic data from the Caseyville Formation, the Pottsville Formation, and the Jackfork Group of the Ouachita Basin to document provenance, delineate drainage divides in the Appalachian foreland-basin system, and comment on the unlikelihood of transcontinental sediment routing from the eastern United States to western United States at this time.\u0000 Two DZ U-Pb age distributions from quartz arenite sandstones of the Caseyville Formation display prominent ca. 1250–950 Ma, 1550–1300 Ma, 1800–1600 Ma, and 3500–3000 Ma ages, consistent with ultimate derivation from Grenville, Midcontinent granite–rhyolite, Yavapai–Mazatzal, and Superior provinces, as well as minor contributions from ca. 500–400 Ma and 2000–1800 Ma grains. Two DZ U-Pb age distributions from sublitharenite sandstones of the Pottsville Formation display prominent ca. 500–400 Ma, 1250–950 Ma, 1550–1300 Ma, and 1800–1600 Ma ages, consistent with ultimate derivation from Appalachian, Grenville, Midcontinent granite–rhyolite, and Yavapai–Mazatzal provinces, as well as minor contributions from ca. 2000–1800 Ma and 3500–3000 Ma grains. The Pottsville Formation samples demonstrate a greater percentage of Appalachian and Grenville ages relative to the Caseyville Formation samples, whereas the Caseyville Formation samples have elevated Yavapai–Mazatzal and Superior percentages relative to the Pottsville. We interpret these differences to suggest parallel fluvial systems in the foredeep and back-bulge depozones of the Appalachian foreland-basin system.\u0000 Like DZ studies of modern deep-sea fans that demonstrate an affinity to feeder fluvial systems, this study demonstrates fidelity between endmember segments of ancient fluvial-to-deepwater systems. Multidimensional scaling (MDS) analysis shows that DZ samples from the Pottsville and Caseyville formations cluster with deepwater Jackfork Group samples, and we infer a source-to-sink relationship from these two distinct source areas to the Ouachita terminal sink. One example of large-scale inclined strata thickness from the Caseyville Formation also suggests a drainage basin area of > 105 km2. Contextualized with these observations, we suggest that the foredeep and backbulge depozones of the Appalachian foreland-basin system steered distinct Early Pennsylvanian rivers across emergent continental shelves during periods of low sea-level, which discharged to distinct slope canyons and sourced > 100-km-long deep-sea fans. Clearly circumscribed, southward- or sout","PeriodicalId":17044,"journal":{"name":"Journal of Sedimentary Research","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2022-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48139091","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The glass ramp of Wrangellia: Late Triassic to Early Jurassic outer ramp environments of the McCarthy Formation, Alaska, U.S.A.","authors":"Y. Veenma, Kayla Mccabe, A. Caruthers, M. Aberhan, M. Golding, S. Marroquín, J. Owens, T. Them, Benjamin C Gill, J. Trabucho Alexandre","doi":"10.2110/jsr.2022.004","DOIUrl":"https://doi.org/10.2110/jsr.2022.004","url":null,"abstract":"\u0000 The marine record of the Triassic–Jurassic boundary interval has been studied extensively in shallow-marine successions deposited along the margins of Pangea, particularly its Tethyan margins. Several of these successions show a facies change from carbonate-rich to carbonate-poor strata attributed to the consequences of igneous activity in the Central Atlantic Magmatic Province (CAMP), which included a biocalcification crisis and the end-Triassic mass extinction. Evidence for a decline in calcareous and an increase in biosiliceous sedimentation across the Triassic–Jurassic boundary interval is currently limited to the continental margins of Pangea with no data from the open Panthalassan Ocean, the largest ocean basin. Here, we present a facies analysis of the McCarthy Formation (Grotto Creek, southcentral Alaska), which represents Norian to Hettangian deepwater sedimentation on Wrangellia, then an isolated oceanic plateau in the tropical eastern Panthalassan Ocean.\u0000 The facies associations defined in this study represent changes in the composition and rate of biogenic sediment shedding from shallow water to the outer ramp. The uppermost Norian to lowermost Hettangian represent an ∼ 8.9-Myr-long interval of sediment starvation dominated by pelagic sedimentation. Sedimentation rates during the Rhaetian were anomalously low compared to sedimentation rates in a similar lowermost Hettangian facies. Thus, we infer the likelihood of several short hiatuses in the Rhaetian, a result of reduced input of biogenic sediment. In the Hettangian, the boundary between the lower and upper members of the McCarthy Formation represents a change in the composition of shallow-water skeletal grains shed to the outer ramp from calcareous to biosiliceous. This change also coincides with an order-of-magnitude increase in sedimentation rates and represents the transition from a siliceous carbonate-ramp to a glass ramp ∼ 400 kyr after the Triassic–Jurassic boundary. Sets of large-scale low-angle cross-stratification in the Hettangian are interpreted as a bottom current–induced sediment drift (contouritic sedimentation). The biosiliceous composition of densites (turbidites) and contourites in the Hettangian upper member reflects the Early Jurassic dominance of siliceous sponges over Late Triassic shallow-water carbonate environments. This dominance was brought about by the end-Triassic mass extinction and the collapse of the carbonate factory, as well as increased silica flux to the ocean as a response to the weathering of CAMP basalts. The presence of a glass ramp on Wrangellia supports the hypothesis that global increases in oceanic silica concentrations promoted widespread biosiliceous sedimentation on ramps across the Triassic to Jurassic transition.","PeriodicalId":17044,"journal":{"name":"Journal of Sedimentary Research","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2022-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44831936","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Paleocene (65–63 and 58.5 ma) marine flooding and 62–60 ma sediment bypass in southern Wyoming, U.S.A.: Implications for Laramide sediment flux to the Gulf of Mexico","authors":"A. Wroblewski, R. Steel","doi":"10.2110/jsr.2021.111","DOIUrl":"https://doi.org/10.2110/jsr.2021.111","url":null,"abstract":"\u0000 Sedimentary structures unique to tidally influenced environments and unambiguously salinity-stressed marine ichnofossil assemblages in the lower Paleocene Ferris and upper Paleocene Hanna formations of Wyoming's Hanna Basin (HB) necessitate major revision of local and regional reconstructions of the Paleocene Western Interior Seaway (WIS). Preserved in sandy estuarine bars, sandy tidal flats, heterolithic distributary channels, bayhead delta, and flood-tide-delta deposits similar those in the modern Trinity River, its bayhead delta, and the San Luis Pass flood-tidal delta on the Texas coast, these these assemblages include Arenicolites, Bergaueria, Fuersichnus, Gyrochorte, Ophiomorpha, Palaeophycus, Planolites, Psilonichnus, Rhizocorallium, Rosselia, Siphonichnus, Skolithos, Spongeliomorpha, Taenidium, Thalassinoides, and tetrapod tracks. Mapping an ∼ 325-m-thick succession of lower Paleocene strata (65 to 63 Ma) around the western HB reveals a series of marine flooding events, each followed by coal accumulation. A similar, 170-m-thick succession of interfingering coastal-plain and restricted-marine strata occurs in the upper Paleocene (58.5 Ma) Hanna Formation, following accumulation of lacustrine and floodplain deposits and an episode of major gravel and cobble progradation from 62 to 60 Ma. These younger ichnofossils record the final major transgression of the WIS and have major implications for the depositional environment of the time-equivalent Waltman Shale in the Wind River Basin to the north and for sediment routing to the Gulf Coast Wilcox sands. Ichnofossils are an underutilized source of physicochemical proxy data that are lifting the veil from the cryptic Paleocene transgressions of the WIS that have for so long remained undetected because of the absence of open-marine body fossils.","PeriodicalId":17044,"journal":{"name":"Journal of Sedimentary Research","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2022-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45566983","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Oligocene–late Miocene basin evolution in the Yengejeh syncline in the Central Iranian Basin in response to the Arabia–Eurasia orogeny","authors":"Najmeh Etemad-Saeed, M. Najafi, Negar Nasirizadeh","doi":"10.2110/jsr.2021.140","DOIUrl":"https://doi.org/10.2110/jsr.2021.140","url":null,"abstract":"\u0000 The Central Iranian Basin has developed during a multi-episodic collision between the Arabian and Eurasian continents since the late Eocene–early Oligocene, following the subduction of the Neo-Tethys Ocean. Herein, we present detailed sedimentological and provenance data of the Oligocene–upper Miocene synorogenic strata, including the unconformity-bounded Lower Red, Qom, and Upper Red formations, in the Yengejeh syncline in the NW termination of Central Iran, to analyze stratigraphy, depositional environments, and provenance. Our results indicate that the sedimentary system has evolved in five stages coeval with regional deformational and volcanic events: a) deposition of the Lower Red Formation in an alluvial fan containing the first appearance of Sanandaj–Sirjan metamorphic clasts sourced from the proximal southwestern Takab Complex, exhumed by the onset of Arabian–Eurasian soft collision in late Eocene–early Oligocene; b) Burdigalian transgression of the Qom Sea and shallow-water carbonate sedimentation influenced by continuous pyroclastic inputs and lava flows from an active volcanic center; c) deposition of the M1 unit of the Upper Red Formation in a continental sabkha in arid climate conditions during Burdigalian–Langhian and the first appearance of internal clasts derived from the folded Qom Formation layers due to the Arabian–Eurasian hard collision; d) fluvial deposition of the M2 unit during the Langhian–Tortonian with sediments derived from the Qom Formation and Takab Complex; and e) deposition of the uppermost siliciclastics of the M2 unit at the edge of an alluvial fan during the late Miocene, after a period of pyroclastic fallout in the Tortonian. In general, the source-to-sink relationship is controlled by the development of tectono-topographic relief in the crystalline core of the Zagros Mountains that configured the source areas in the Sanandaj–Sirjan metamorphic belt supplying the NW termination of Central Iran through a well-developed drainage system towards the Caspian Sea. Coeval with the deformational events, magmatic phases supplied a large volume of volcaniclastic inputs both before the Neo-Tethys slab break-off and after the hard continental collision. The depositional environments and provenance of the studied sedimentary record provide an analog for the development of synorogenic hinterland basins worldwide along with the well-known Altiplano Basin of the Andes and Hoh Xil Basin of Tibet.","PeriodicalId":17044,"journal":{"name":"Journal of Sedimentary Research","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2022-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46281918","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The supply-generated sequence: A unified sequence-stratigraphic model for closed lacustrine sedimentary basins with evidence from the Green River Formation, Uinta Basin, Utah, U.S.A.","authors":"James H. Gearon, C. Olariu, R. Steel","doi":"10.2110/jsr.2021.096","DOIUrl":"https://doi.org/10.2110/jsr.2021.096","url":null,"abstract":"\u0000 Closed lakes and oceans are stratigraphically distinct systems. However, closed-lake stratigraphy is often interpreted using conventional sequence stratigraphic concepts which were generated for marine settings. As a consequence, lacustrine stratigraphy has long been vexing and applied on an ad-hoc basis. To remedy this, we present a novel, unified sequence stratigraphic model for hydrologically closed (endorheic) basins: the Supply-Generated Sequence (SGS) Model. This model was generated to interpret our outcrop-based correlation—the largest to date at ∼ 30 km—across the Sunnyside Interval member of the middle Green River Formation in Nine Mile Canyon near Price, Utah, USA. The SGS model is based on the fundamental sedimentological and hydrodynamic differences between closed lakes and marine settings wherein the relationship between water discharge and sediment discharge is highly correlated. The SGS model divides packages of genetic lacustrine strata by bounding correlative surfaces, conformable or unconformable, separating facies and surfaces associated with low clastic supply (e.g., carbonates, mudstones, or exposure surfaces) from facies characteristic of relatively higher amounts of clastic supply (subaerial channelized sandstones, subaqueous siltstones, and pedogenic mudstones). We use the SGS model to correlate regional sequences at a higher resolution than previous interpretations and find the greatest amount of clastic deposition occurs during periods of lake-level rise, indicating that the SGSs are characteristically transgressive. Additionally, this model removes the implicit and explicit base-level assumptions of previous sequence stratigraphic models while being agnostic to the source of increased sediment discharge and therefore generalizable to other closed lacustrine settings. We use the high-resolution supply-generated sequences (meters thick) to argue for a climatic origin of the cyclic Sunnyside interval deposits based on sequence durations (40–50 kyr), and aligning sequences with recognized early Eocene transitory hyperthermal event timing and their associated climatic shifts across the region, increasing riverine discharge of sediment and water.","PeriodicalId":17044,"journal":{"name":"Journal of Sedimentary Research","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2022-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48885276","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tectonostratigraphic and paleoenvironmental settings of host-replacing phreatic calcrete hardpans developed at basin margins in the Upper Devonian Kinnesswood Formation of southwest Scotland","authors":"P. Jutras","doi":"10.2110/jsr.2022.003","DOIUrl":"https://doi.org/10.2110/jsr.2022.003","url":null,"abstract":"\u0000 In the Firth of Clyde area of southwest Scotland, the Famennian Kinnesswood Formation includes an interval of massive, host-replacing phreatic calcrete hardpan (HRPCH), the likes of which have been documented only at few locations and few intervals in geological history. The HRPCH is found only at basin-margin shoulders, where the Kinnesswood Formation succession is thin and incomplete. The isles of Bute and Great Cumbrae provide well exposed sections in which adjacent shoulder and trough successions can be correlated and compared to clarify the tectonostratigraphic and paleoenvironmental settings of the HRPCHs. In the Cumbraes Trough, above a thin interval of peritidal limestone, the middle part of the Kinnesswood Formation (lower part of the Foul Port Member) is pervasively disturbed by large syndepositional dewatering structures interpreted to be products of the intermittent deposition and dissolution of evaporites. These structures occur at approximately the same stratigraphic interval as the HRPCHs on the isles of Bute and possibly Arran. The HRPCH in Bute is interpreted to have developed on a syndepositional shoulder adjacent to a growth fault (the Kerrycroy Fault) delimiting a trough that accommodated intermittent seawater incursions in a restricted, evaporitic setting. This is consistent with the current model for HRPCH formation, which involves the mixing of fresh groundwater issued from source areas with the high pH groundwater that surrounds evaporitic basins. A significant increase in silica solubility paired with a decrease in calcite solubility occurs in the mixing zone, thus promoting the thorough replacement of silicates with calcrete.","PeriodicalId":17044,"journal":{"name":"Journal of Sedimentary Research","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2022-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43108996","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Maastrichtian atmospheric pCO2 and climatic reconstruction from carbonate paleosols of the Marília Formation (southeastern Brazil)","authors":"Maurícius Nascimento Menezes, P. Dal’ Bó, Jon J Smith, A. G. Rodrigues, Á. Rodríguez-Berriguete","doi":"10.2110/jsr.2021.060","DOIUrl":"https://doi.org/10.2110/jsr.2021.060","url":null,"abstract":"\u0000 Paleosols are the product of ancient physical, chemical, and biological processes on the Earth's surface and, as such, may record information that can be used to reconstruct the paleoatmospheric and paleoenvironmental conditions under which they formed. In Brazilian continental sedimentary successions, few studies using ancient soils have focused on the relationship between paleopedogenesis and paleoclimate. The Marilia Formation is a 160-m-thick section of the Bauru Basin in which ∼ 66% of the deposits show some evidence of pedogenic modification as paleosols. In this paper, paleosol profiles in the Marilia Formation containing thick calcrete intervals are described and attributed to three pedotypes: Avencas, Monte Alto, and Garça. Macro and microscopic pedogenic features of each pedotype are described in detail. Moreover, the analysis of clay mineralogy, whole-rock geochemistry, and stable-isotope composition are used to define pedogenic processes, paleoclimate proxies, and atmospheric pCO2 estimates. The Avencas pedotype is composed of six polygenetic profiles with different phases of carbonate precipitation, clay illuviation, and biogenic actions. The Monte Alto pedotype is moderately developed and composed of calcic horizons formed mainly by rhizoliths, with higher degrees of calcification and oxidation compared to Avencas profiles. The Garça pedotype is well developed with five polygenetic profiles presenting high carbonate content and low accumulation of clay minerals (CIA-K) and leaching. Estimates of paleoprecipitation and paleotemperature from the studied paleosols using climofunctions of molar ratio of base to alumina, depth of carbonate accumulation, salinization, oxygen composition, and paleosol weathering index proxy (PWI) show values ranging from 242 to 718 mm/yr and 11° to 14°, respectively. Climofunction values suggest a paleoclimate of semiarid to subhumid during deposition of the Marília Formation. The climate data also suggests that during the Maastrichtian, the Bauru Basin was geographically within the Southern Hot Arid Belt zone, though showing strong influence of the lower latitudinal Equatorial Humid belt. Furthermore, atmospheric pCO2 values calculated from pedogenic carbonates may correlate with a cooling interval during the latest Maastrichtian (68.5–66.25 My).","PeriodicalId":17044,"journal":{"name":"Journal of Sedimentary Research","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2022-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43192433","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 analysis of crevasse-splay systems from modern fluvial settings","authors":"M. Rahman, J. Howell, D. Macdonald","doi":"10.2110/jsr.2020.067","DOIUrl":"https://doi.org/10.2110/jsr.2020.067","url":null,"abstract":"\u0000 Although crevasse splays are a common constituent of many fluvial and fluvio-deltaic systems, they remain less well understood than the channel deposits in those settings, especially with respect to controls on their occurrence, distribution, and geometry. The current study aims to redress this balance and investigate controls on 1) splay formation and occurrence and 2) splay size and geometry. The study has used Google Earth-based satellite imagery to examine crevasse-splay deposits from eight modern fluvial systems. A total of 1556 crevasse splays were identified using imagery from 1984 to 2020. Most of the splays (c. 70%) occur on the outer sinuous river bank with offtake angles ranging from 10° to 140° (mean 75°) to the channel flow direction. Three different types of splays have been identified: i) single crevasse splays, ii) laterally amalgamated crevasse splays, and iii) crevasse-splay complexes. The areal extent of splay bodies varies widely and ranges from less than 1 km2 up to 221 km2. The single crevasse splays are the primary and smallest form of splay, with an average area of 0.61 km2. Compensational stacking or progradation significantly increase the splay area and form laterally amalgamated splays and splay complexes, respectively. The average areal extent of laterally amalgamated splays is 1.33 km2, and of splay complexes, 39 km2.\u0000 The climate, discharge, floodplain morphology, vegetation, trunk channel slope, sinuosity, and sediment load primarily control the occurrence, geometry, and dimensions of crevasse splays. Results demonstrate that sparse or no floodplain vegetation favors the formation of elongated tongue-shaped crevasse splays while densely vegetated floodplains produce more lobate splays. The highest splay frequency occurs in systems where the river experiences sudden high magnitude variation in discharge, has a low cross-sectional area, and noncohesive bank materials. Larger splay size is correlated with lower river slope angles and higher sinuosity, discharge, and floodplain relief. Channel size has little influence on the extent of splays. This work suggests that autogenic factors such as trunk-channel slope and sinuosity are more influential in arid–semiarid settings while allogenic factors such as discharge are important in temperate–equatorial settings.","PeriodicalId":17044,"journal":{"name":"Journal of Sedimentary Research","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2022-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47381949","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Microbial-mat colonization of modern gravel deposits in a siliciclastic coastal setting","authors":"Jerónimo Pan, D. Cuadrado, N. Noffke","doi":"10.2110/jsr.2022.028","DOIUrl":"https://doi.org/10.2110/jsr.2022.028","url":null,"abstract":"\u0000 Microbial mats are layered consortia of microorganisms colonizing surface sediments that alter their physical and chemical characteristics. The northern Patagonia coastline (Argentina) includes gravel deposits (termed rodados Patagónicos) accumulated during the Pleistocene and Holocene by high-energy hydrodynamic processes. In this area, surface sediments in a relict tidal channel (Paso Seco; 40° 38′ 27″ S, 62° 12′ 55″ W) are extensively colonized by microbial mats, appearing to overgrow exposed gravel deposits. To date, such substrates have not been reported as suitable for the development of microbial mats. The objectives of this paper are: 1) to describe the mechanisms of microbial baffling, trapping, and binding of sedimentary particles, and biostabilization that enable epibenthic microbial mats to develop on gravel substrates, 2) to relate microbial mat growth to a variety of hydrodynamic conditions, and 3) to describe resulting microbially induced sedimentary structures (MISS). Our hypothesis is that the alternation of episodic seawater flooding, stagnation, and draining with subsequent subaerial exposure and desiccation are the controlling factors for mat development on gravel. Once stagnant, mud-size sediment particles settle from suspension. At the same time, an initial biofilm may become established on the bottom, using the fine-grained material as substrate. Subsequently introduced particles are baffled, trapped, and bound into the developing biofilm matrix. During the Austral winter comparatively higher values for chlorophyll a and organic matter point towards increased growth of the microbial mat during this season. With increasing coherence, the developing microbial mat may encroach onto individual pebbles, ultimately engulfing them. Eventually, a mature, epibenthic microbial mat levels the sedimentary surface. Hydrodynamic reworking during flooding produces MISS such as mat chips and flipped-over mats.","PeriodicalId":17044,"journal":{"name":"Journal of Sedimentary Research","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2022-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42166813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}