Microbial mat-induced sedimentary structures in siliciclastic sediments: Examples from the 1.6 Ga Chorhat Sandstone, Vindhyan Supergroup, M.P., India |
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Authors: | Subir Sarkar Santanu Banerjee Pradip Samanta Silambuchelvan Jeevankumar |
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Institution: | (1) Department of Geological Sciences, Jadavpur University, 700 032 Kolkata, India;(2) Department of Earth Sciences, Indian Institute of Technology Bombay, Powai, 400 076 Mumbai, India |
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Abstract: | This paper addresses macroscopic signatures of microbial mat-related structures within the 1.6Ga-old Chorhat Sandstone of
the Semri Group — the basal stratigraphic unit of the Vindhyan succession in Son valley. The Chorhat Sandstone broadly represents
a prograding succession of three depositional facies ranging from shallow shelf to coastal margin with aeolian sandsheet.
The mat-mediated structures were generated because of plastic or brittle deformation of sand, turned cohesive and even thixotropic
because of microbial mat growth. Mat growth also favoured abundant preservation of structures that usually have low preservation
potential. Prolific growth of microbial mat in the subtidal to intertidal zone of the Chorhat sea was facilitated due to lack
of grazing and burrowing activities of organisms in the Precambrian. It further indicates low rate of sedimentation between
the storms, as also attested by frequent superposition of storm-beds, even near the storm wave base. It also reduces erosion
and that, in turn, would imply low sediment concentration in flows leading to development of bedforms that are likely to be
smaller in size and isolated from each other in a single train in contrast to those that form in mat-free sands. |
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Keywords: | Microbial mat Proterozoic siliciclastics mat-induced structures 1 6 Ga-old Chorhat Sandstone |
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