Alluvial Sedimentary Records in Indian Precambrian Basins: Implications Toward Unique Precambrian Sedimentary Environment?

Abstract

“Present is the key to the past”—in this all-inclusive uniformitarians’ geological panacea, the Precambrian continental sedimentation system stands out as an odd candidate. The distinctive nature of Precambrian alluvial sedimentation, not analogous to their Phanerozoic counterparts, is highlighted in literature in the absence of rooted vegetation, soil, and an overall greenhouse atmospheric condition. Documentation from Precambrian alluvial deposits around the globe suggests a sedimentation pattern dominated by scree cones, alluvial fans, and braid-plains under the combined effects of aggressive weathering and absence of vegetation; ephemeral braid-plains convincingly outweigh the other alluvial systems in the rock record. It is also surmised that Precambrian fluvial systems, unlike their Phanerozoic-modern analogs, maintained unequivocal ephemeral character across different climatic zones with very less chance of assuming meandering channel planform in absence of buffering effects of rooted plant and adequate mud. Local ponding of muddy sediments, though visualized in some rare cases, was mostly connected with the generation of local paleoslope and unusual riverine hydrology. Recent studies, however, raised a question about the actual paucity of mud, documented meander channel planforms from Precambrian fluvial records, and drew a parallel between the character of the Pre-Silurian alluvial plain on the surface of Earth and meander channel planforms on the Martian surface, interpreted from satellite imagery data. From the collation of data on alluvial deposits from a number of Indian Precambrian basins, augmented by new data from the Bayana basin, a Paleoproterozoic basin in the North Delhi fold belt, the present study attempts to document nuances and intricacies in Precambrian alluvial sedimentation motif that include facies architecture and paleohydrology. From an extensive, though not exhaustive, database, the study intends to claim the establishment of a meander channel-form in Precambrian river systems at a local scale in areas of low discharge and availability of higher silt and mud.