Architecture of a tide-influenced, wave dominated shallow-marine deposit from a Paleoproterozoic rift setting: Example from the Badalgarh Formation, Bayana basin, Rajasthan, northwest India

Abstract

A ~125 m thick shallowing-upward arenaceous succession from the Badalgarh Formation, Bayana basin, India provided the opportunity to document shelf to foreshore transition from a paleoproterozoic rift set-up. Process-based facies analysis allowed identification of 12 different shallow-marine facies types, grouped under four different facies associations namely (i) lower offshore or open shelf, (ii) upper offshore to distal lower shoreface, (iii) lower to middle shoreface and (iv) upper shoreface to foreshore. From unequivocal dominance of wave- and storm-generated features and fortuitous documentation of tide-generated structures in upper offshore, lower and middle shoreface settings, we infer a tide-influenced, wave-dominated coast at the Badalgarh Sea. From measurement of different vector attributes through the studied succession, we infer (i) near east–west orientation for the Badalgarh shoreline, (ii) storm deposits as products of shore-perpendicular return flow, and (iii) tidal peak flow at a high angle with the shoreline and confined in the upper offshore, lower and middle shoreface settings. A gradational transition from offshore to lower shoreface and, in turn, to middle and upper shoreface suggests accretionary character for the Badalgarh shoreface in a high-gradient rift setting. Overlying deep water (distal offshore) argillaceous marine strata, the arenaceous shallowing-upward Badalgarh succession is interpreted as a product of highstand systems tract (HST) constituted of stacked tens- to hundreds of meter-thick shallowing-upward depositional cycles. Since the abrupt shift in facies type (shallow to deep water) across the upper boundaries of depositional cycles is not unambiguous, we intend to assign these cycles as genetic stratigraphic cycles or T-R cycles over ‘parasequence’.