Granulometric and facies analysis of Middle–Upper Jurassic rocks of Ler Dome, Kachchh, western India: an attempt to reconstruct the depositional environment
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Date
2019-04
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Wydawnictwo Naukowe UAM
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Abstract
Grain size analysis is an important sedimentological tool used to unravel hydrodynamic conditions, mode of trans-
portation and deposition of detrital sediments. For the present study, detailed grain size analysis was carried out in
order to decipher the palaeodepositional environment of Middle–Upper Jurassic rocks of the Ler Dome (Kachchh,
western India), which is further reinforced by facies analysis. Microtextures were identified as grooves, straight steps
and V-shaped pits, curved steps and solution pits suggesting the predominance of chemical solution activity. Grain
size statistical parameters (Graphic and Moment parameters) were used to document depositional processes, sedimen-
tation mechanisms and conditions of hydrodynamic energy, as well as to discriminate between various depositional
environments. The grain size parameters show that most of the sandstones are medium- to coarse-grained, moderately
to well sorted, strongly fine skewed to fine skewed and mesokurtic to platykurtic in nature. The abundance of medi-
um- to coarse-grained sandstones indicates fluctuating energy levels of the deposition medium and sediment type of
the source area. The bivariate plots show that the samples are mostly grouped, except for some samples that show a
scattered trend, which is either due to a mixture of two modes in equal proportion in bimodal sediments or good sorting
in unimodal sediments. The linear discriminant function analysis is predominantly indicative of turbidity current de-
posits under shallow-marine conditions. The C-M plots indicate that the sediments formed mainly by rolling to bottom
suspension and rolling condition in a beach subenvironment. Log probability curves show that the mixing between the
suspension and saltation populations is related to variable energy conditions.
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Keywords
Grain size analysis, hydrodynamic conditions, microtextures, sedimentation, marine environment
Citation
Geologos, 2019, 25, 1, 51-73.
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ISBN
978-83-232187-4-6
ISSN
1426-8981