DOI: 10.5176/2251-3361_GEOS12.119
Authors:
Abstract: North West Saudi Arabia provides a unique opportunity to examine the exposures of the Nutaysh member of the Burqan Formation, of early Miocene age. The Nutaysh member is a sand-dominated succession consisting of thickly bedded conglomeratic sandstone, alternating with moderate- to poorly sorted subordinate thinly bedded and finer grained beds of siltstone, shale and marl. Regardless of the bed thickness, all the beds are associated with the deposits of high density turbidity currents. These features and also presence of the abundant bioclastic debris and trace fossil assemblages indicate mass flow sedimentation into a shallow to marginal marine environment. In this study, the Markov chain analysis technique was applied to characterize the pattern and the cyclicity of Nutaysh member lithofacies. The Markov model recognizes natural successions of three lithofacies. These are; the stacked, massive and crudely graded bedded layers ranging from conglomeritic sandstone into coarse-grained sandstone (lithofacies A), overlain by the horizontal bedded, coarse-to-medium grained sandstone (lithofacies B), overlain by the thin bedded, rippled and biotturbated shaley siltstone and capped by the marl (lithofacies C). The model also, recognizes the existence of several random (irregular) transitions (e.g. transition from the litofacies A to the lithofacies C and from the lithofacies B to the lithofacies A). These random transitions are most probably due to slight modification in the sedimentary record by disturbing phenomena, such as relative rest associated with reduced tectonic activity; or periods dominated by sea level rise that alternated with periods dominated by tectonically controlled coarse clastic sedimentation.
Keywords: Markov Chain, Turbidite, Sandstone, Saudi Arabia
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