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  Subjects -> GEOGRAPHY (Total: 493 journals)
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Journal of Sedimentary Research
Journal Prestige (SJR): 1.347
Citation Impact (citeScore): 2
Number of Followers: 4  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1527-1404 - ISSN (Online) 1938-3681
Published by Society for Sedimentary Geology Homepage  [1 journal]
  • Sedimentological and geochemical characterization of microbial mats from
           Lagoa Vermelha (Rio de Janeiro, Brazil)

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      Abstract: ABSTRACTThe presence of microbialites in the hypersaline lagoons of Rio de Janeiro is especially important in the study of recent analogs of carbonate rocks with microbial origins, mostly after the discovery of giant petroleum reservoirs in the Brazilian pre-salt section and their similarities with stromatolites from Lagoa Salgada (Rio de Janeiro State). Many studies have been conducted to analyze the biology, geochemistry, mineralogy, and geomicrobiology of these microbialites. This paper, however, focuses on the petrography, sedimentology, and geochemistry of recent and superficial microbial mats from Lagoa Vermelha to understand the interaction of carbonate and siliciclastic grains with an organic matrix and discuss their similarities and differences with pre-salt rocks. A sedimentologic description was performed to understand the sediment dynamics in microbial mats. A petrographic description involved the characterization of components and textures in microscale. Furthermore, geochemical analyses were performed using scanning electron microscopy and X-ray diffraction for detailed mineralogical characterization. This multitechnique study showed the lamellar and cracked texture of the matrix being displaced by biologically induced carbonate growth and siliciclastic grains. In addition, chemical analysis showed the concentration of magnesium and silica in the matrix, with the absence of Mg-clay minerals. Even though the studied microbial mats present relevant similarities with some pre-salt facies, a microbially dominated genesis for the pre-salt limestones cannot be supported by the studied data.
      PubDate: Thu, 30 Jun 2022 00:00:00 GMT
       
  • Sediment transfer from shelf to deepwater slope: How does it happen'

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      Abstract: ABSTRACTThe processes that transport sediment from the coastline to the shelf edge are key components of the sedimentary source-to-sink system, determining basin-margin building, deepwater deposition, organic-material accumulation, and the long-term carbon cycle. Research on shelf sediment transport has been aided recently by advances in modeling and marine technology. In this study we provide a much needed review of up-to-date findings on how sediment moves from the outer shelf onto the upper slope, and we summarize four dominant shelf-to-slope drivers: 1) river currents, 2) reworking storm waves and longshore currents, 3) strong tidal currents supplementing river outflow, and 4) small-scale to very large-scale gravity collapse of the shelf-edge area.
      PubDate: Thu, 30 Jun 2022 00:00:00 GMT
       
  • Paralic sedimentology of the Mussentuchit Member coastal plain, Cedar
           Mountain Formation, central Utah, U.S.A.

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      Abstract: ABSTRACTAlthough intensified work on the volcaniclastic-rich sediments of the fossil-bearing Mussentuchit Member (uppermost Cedar Mountain Formation, Utah) has provided a refined chronostratigraphic framework, paleoenvironmental interpretations remain cryptic. To resolve this, we performed facies analysis and architectural reconstruction on exposed Mussentuchit Member outcrops south of Emery, central Utah, USA. Contrary to previous interpretations (fluvial, lacustrine), we identified a broad suite of facies that indicate that deposition occurred on the landward part of a paralic depocenter, influenced by both distal alluvial and proximal coastal systems. We conclude that the Mussentuchit Member was a sink for suspension-settling fines with most undergoing pedogenic alteration, analogous to the modern coastal plain of French Guiana (Wang et al. 2002; Anthony et al. 2010, 2014). However, this landward paralic depocenter was not uniform through time. Sedimentological evidence indicates landscape modification was ongoing, influenced by an altered base-level (high groundwater table, long residency of water in sediments, shifts in paleosol types, heavier to lighter δ18O, and distinct shifts in relative humidity (ε); common in coastal settings). If the above data is coupled with recent age data, we interpret that the Mussentuchit Member correlates to the S.B. 4 Greenhorn Regression (Thatcher Limestone) of the adjacent Western Interior Seaway to the east. As a landward paralic depocenter, the Mussentuchit would have been sensitive to base-level conditions in response to ongoing tectonic processes pushing the foredeep east, and lower paleo-CO2 levels coupled with a minor global sea-level fall (brief glacial phase) just before to the Cenomanian–Turonian Thermal Maximum. Altogether, our results not only strengthen linkages in the central Western Interior Seaway, but simultaneously results in novel linkages to near-coeval paralic depocenters across mid-Cenomanian North America.
      PubDate: Mon, 27 Jun 2022 00:00:00 GMT
       
  • The geomorphological distribution of subaqueous tufa columns in a
           hypersaline lake: Mono Lake, U.S.A.

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      Authors: Keevil CE; Rogerson M, Parsons DR, et al.
      Abstract: AbstractUnderstanding the flow of carbon through hyperalkaline lakes is a key means of understanding their biogeochemistry, sedimentology, and their paleoenvironmental and paleoclimatic records. Furthermore, understanding how mineral precipitation is regulated in these lakes can provide insights into how their sequestration of carbon can be managed. We report geophysical surveys of Mono Lake, California, USA, which show unanticipated geomorphological control on the recent/contemporary formation of lacustrine carbonate formations (“tufa”). Acquired shallow-penetration seismic data show a fault zone below the lake floor, but despite the regional evidence for geothermal waters rising up these fractures, we find no evidence for tufa precipitation at the surface exposure of this structure, either in the seismic data or in the swath bathymetry. However, we do find sub-lacustrine tufa columns in these data elsewhere, which is the first time these have been reported directly. We find and report on a strong link between column location and meteoric Ca supply to the lake, with the latter sourced either through surface runoff or groundwater. For example, a region close to a creek inlet has more frequent and larger tufa bodies, which grow at a wider depth range than another region far from an inlet but close to the fault. This demonstrates the importance of meteoric water ingress in regulating carbonate mineral formation in these basins, and raises the possibility that management of water within the catchment could be a means to enhance carbon capture in natural and artificial hyperalkaline lakes.
      PubDate: Tue, 21 Jun 2022 00:00:00 GMT
       
  • Stratal characteristic and depositional origin of two-part (Mud-poor
           overlain by mud-rich) and associated deep-water strata: Components in a
           lateral depositional continuum related to particle settling in negligibly
           sheared mud-rich suspensions

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      Authors: Ningthoujam J; Wearmouth C, Arnott RC.
      Abstract: AbstractDeep-marine strata consisting of a sandy basal part overlain sharply by a muddier and mud-clast-rich upper part are increasingly being recognized in the deep-marine sedimentary record, and have been termed linked debrites, cogenetic debrite–turbidite beds, hybrid event beds, transitional-flow deposits, and bipartite beds. These composite strata are generally reported to develop downflow of clean (less muddy) sand, but the variable distance (hundreds of meters to tens of kilometers) over which this lithological change is reported to take place has resulted in a variety of physical depositional models. As such, the details about the origin and spatial evolution of these admixed sand–mud strata still remain poorly understood. Part of this uncertainty is that many earlier studies, with a few exceptions, have been based on macroscopic observations in drill core or discontinuous outcrops, and therefore interpreted bed continuity is based on similarity of textural or other sedimentological attributes. However, in slope to proximal basin-floor deposits of the Neoproterozoic Windermere Supergroup, and distal basin-floor deposits of the Ordovician Cloridorme Formation, exceptional outcrop exposure permitted individual two-part (bipartite) facies and their associated strata to be continuously traced and lithological changes to be documented along the strike of the outcrop.In both the Windermere and the Cloridorme, the bipartite facies consists of a lower sandy (25–60% matrix) part overlain sharply by a muddier (40–80% matrix), commonly mud-clast-rich upper part, and occurs downflow of muddy sandstone and upflow of sandy mudstone in a hundreds-of-meters long proximal to distal depositional continuum. These strata are then overlain everywhere by a thin- to very thin-bedded, traction-structured sandstone and/or silty mudstone cap. Notably, the interface separating the lower sand-rich part from the upper mud-rich part in the bipartite part of the depositional transect is always planar in the Windermere, but often alternates between planar and irregular in the Cloridorme. The continuum is interpreted to represent deposition downflow of an avulsion node that resulted in erosion of the local mud-rich seafloor and charged the flow with fine-grained sediment, resulting in increased effective fluid viscosity and significant changes in the characteristics, intensity, and transfer of fluid turbulence needed to maintain the particle suspension. Collapse of the suspension and development of overcapacity conditions resulted in rapid particle settling in the now rapidly depleting and negligibly sheared mud-enriched suspension that formed along the margins of the avulsion-wall jet in proximal-basin-floor and slope deposits (Windermere), or at the downflow terminus of the flow in more distal basin-floor deposits (Cloridorme). Additionally, when normalized to the total length of the continuum, the transition from muddy sandstone to bipartite facies and bipartite facies to sandy mudstone are equally proportioned in all examples, suggesting that, once formed, the depleting suspension evolved in a spatially systematic and dimensionally proportionate manner—a consistent depositional evolution difficult to reconcile with two mechanistically different parts to the flow. Moreover, differences in the morphology of the bipartite interface (i.e., planar vs. irregular) is not a primary depositional feature, but instead is interpreted to be a consequence of local postdepositional deformation of a previously continuous planar surface.
      PubDate: Mon, 13 Jun 2022 00:00:00 GMT
       
  • Quantifying river avulsion activity from satellite remote sensing:
           Implications for how avulsions contribute to floodplain stratigraphy in
           foreland basins

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      Authors: Valenza JM; Edmonds DA, Weissmann GS.
      Abstract: ABSTRACTThe rarely witnessed process of river avulsion repositions channels across floodplains, which influences floodplain geomorphology and stratigraphic architecture. The way avulsions redirect water and sediment is typically generalized into one of two styles. Avulsions proceeding through rapid channel switching and producing little to no floodplain disturbance are annexational, while those that involve sequential phases of crevassing, flooding, and eventual development of a new channel are progradational. We test the validity of these avulsion style categories by mapping and characterizing 14 avulsion events in Andean, Himalayan, and New Guinean foreland basins. We use Landsat data to identify how avulsions proceed and interpret the possible products of these processes in terms of geomorphic features and stratigraphy. We show that during annexation the avulsion channel widens, changes its meander wavelength and amplitude, or increases channel thread count. During progradation, avulsion channels are constructed from evolving distributary networks. Often beginning as crevasse splays, these networks migrate down the floodplain gradient and frequently create and fill ponds during the process. We also see evidence for a recently defined third avulsion style. Retrogradation involves overbank flow, like progradation, but is marked by an upstream-migrating abandonment and infilling of the parent channel. Avulsion belts in this study range from 5 to 60 km in length, and from 1 to 50 km in width. On average, these events demonstrate annexational style over 22.4% of their length. Eleven of 13 events either begin or end with annexation, and seven both begin and end with annexation. Only one event exhibited progradation over the entire avulsion-belt length. While there are many documented examples of purely annexational avulsions, we see little evidence for completely progradational or retrogradational avulsions, and instead suggest that a given avulsion is better envisioned as a series of spatiotemporal phases of annexation, progradation, and retrogradation. Such hybrid avulsions likely produce significantly greater stratigraphic variability than that predicted by the traditional end-member model. We suggest that a time-averaged, formation-scale consideration of avulsion products will yield more accurate characterizations of avulsion dynamics in ancient fluvial systems.
      PubDate: Wed, 01 Jun 2022 00:00:00 GMT
       
 
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