Precambrian basin-margin fan deposits: Mesoproterozoic Bagalkot Group, India

Confined between an unconformity below and a granular lag succeeded by thoroughly wave-featured sandstone, and argillite-carbonate above, the coarse and poorly sorted clastic sedimentary rocks of the basal Ramdurg are interpreted as a base-level lowstand product, for which the sedimentation rate exceeded the rate of space creation for sediment accumulation. Consequently, the fan succession as a whole is coarsening-upward. Fluvial sections, nonetheless, fine upward as the depositional slope gradient became progressively reduced with aggradation of channels. Tectonics-related slope variation along and across the basin-margin, devoid of vegetation, dictated the sediment distribution and sequence building pattern primarily. Eventual termination of this basin-margin depositional system was caused by later enhancement in the rate of base-profile rise.