Red Bed Sands of Visakhapatnam District: A Review of Their Formation, Sedimentology, Mineralogy, Weathering Processes, and Polygenetic Depositional Environments.

Abstract: The red bed sands of the Visakhapatnam coastal region form one of the most distinctive Late Quaternary sedimentary archives along the East Coast of India. These ferruginous deposits, characterized by their red to reddish-brown colours imparted by iron bearing minerals of hematite and goethite coatings, exhibit a multicyclic and polygenetic origin caused by deep weathering of Eastern Ghats crystalline rocks, fluvial transport, aeolian reworking, and coastal geomorphic adjustments. Four major litho-units-yellow sands, reddish-brown sands, brick-red sands, and light-yellow sands reflect marked variability in grain size, sorting, heavy-mineral assemblages, and pedogenic features such as duricrusts and calcretes. Textural and petrographic characteristics indicate that the basal yellow sands were deposited under high-energy fluvial conditions, whereas the overlying reddish-brown and brick-red sediments record enhanced chemical alteration of Fe-bearing minerals and semi-arid pedogenic episodes. The upper light-yellow sands, resembling modern coastal dune deposits, reflect aeolian reworking during phases of lowered oxidation. The combined influence of monsoonal climate, sea-level oscillations, neotectonic uplift, and coastal processes contributed to the complex stratigraphic architecture of these red sands. This review synthesizes existing sedimentological, mineralogical, and geomorphic studies to clarify the origin, weathering pathways, and depositional environments of the Visakhapatnam red sands, while identifying key research gaps for future geochemical, chronological, and provenance analyses.

Keywords: Red bed sands of Visakhapatnam, Eastern Ghat Mobile Belt, polygenic origin, bad land topography, tropical weathering, depositional environment.