Uplift and erosional history of the Deccan Traps, India: Evidence from laterites and drainage patterns of the Western Ghats and Konkan Coast

The Western Ghats escarpment in the western coastal region of peninsular India is locally capped by plateau remnants on which a regional high-level laterite carapace is preserved. Geochemical “fingerprinting” studies show that the laterite has been developed from a protolith of Panhala Formation basalts, the youngest known formation of the Deccan sequence. The high-level laterite is in detail structurally concordant with its underlying basalts, and hence it is concluded that it represents the original top of the lava pile. A younger, low-level, laterite carapace is developed on the Konkan plain below the escarpment where it lies discordantly on basalts of the Ambenali and Poladpur formations, from which it developed in situ. The low-level laterite rises topographically northwards in response to differential uplift, probably at a maximum in the Nasik region. The main structures of the Ghats region, excluding the coastal monocline, are the Nasik dome and the Mahabaleshwar anticline. These have no effect on regional drainage patterns, and it is argued that they are largely secondary features, developing in response to post-volcanic uplift.