Although the similarities between depositional processes and products as well as the analogous controls on basinfilling and evolution appear to have enjoyed great uniformity throughout the sedimentary rock record, a noticeable distinction exists in the rates and intensities of a broad range of geological processes in the Precambrian epoch. This paper searches for distinctiveness in the Precambrian sedimentary record, both siliciclastic and carbonate, through an extensive, though not exhaustive, review of the relevant literature augmented by new observations. While differences in Precambrian deltaic, aeolian, glacial and possibly also lacustrine deposits and settings appear to have been small, their large-scale development was controlled largely by a combination of temporal and geodynamic influences, essentially of global compass. In this regard the onset of the supercontinent cycle and major perturbations in palaeo-atmospheric composition appear to have been significant. Marine environments provide a 2 poor platform for Precambrian -Phanerozoic comparisons of sedimentation patterns, as those from the former period are preserved almost exclusively in epeiric settings, an environment essentially lacking on modern Earth. For the shallow marine carbonates, biological mediation of chemical sediment deposition changed radically from dominance by microbial biota in the Precambrian to a combination of metazons, protozoans and algae for the skeletal carbonates of the Phanerozoic. Despite it being widely recognized that Precambrian channel systems were braided in all environments (deltaic, tidal, alluvial, fluvial) as a consequence of the lack of vegetation and poor development of soils, the fluvial setting has some enigmatic aspects. Amongst these is evidence for ponding of muddy detritus in apparently sandstone bed-load dominated braided systems, with effects on local palaeoslopes which have resulted in unusual palaeohydraulic parameters for Precambrian fluvial systems. This is perhaps a field of research which holds greater promise when investigating sedimentation patterns prior to the Phanerozoic.

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Three-dimensional facies variability in coarse clastic sedimentary rocks (breccia, conglomerates and coarse-grained sandstones) at the base of the Ramdurg Formation suggests terrestrial scree and fans giving way downslope to fluvial sediments along the margin of the Mesoproterozoic Bagalkot basin in India. In consistency with the basic tenet of Precambrian alluvial sedimentation, fluvial architectural elements and field location-specific consistency in channel-flow direction support an invariably braided pattern for the rivers, although the architectural element-packaging pattern does show distinct changes downslope, with channel belts thinning and becoming more regular in their geometry. With possible persistence of a semi-arid climate, downslope change in flow durability in the channels was controlled primarily by water discharge, depending on position of the channels with respect to the mean level of the water table-basin-margin slope intersection.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 openUP 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 basinmargin depositional system was caused by later enhancement in the rate of base-profile rise.