Joyjeet Sen, Arnab Roy , Nibir Mandal

The eastward tilting of the Indian Peninsular (IP) plateau has been a topic of ongoing debate in geoscience. This study introduces a fresh geodynamic perspective, employing extensive topographic analyses to identify the mechanisms behind this tilting. By analyzing the eastward-flowing river systems in relation to the plateau’s tilt, we constructed a series of east-west topographic profiles using digital elevation models (DEM). Our findings indicate a systematic increase in eastward slopes (θ = 0.008° to 0.3°) from the northern boundary to the southern tip of the plateau. Large-scale thermo-mechanical simulations reveal that the configuration of the Indian plate plays a crucial role in driving this tilt. Specifically, we observe that the older lithosphere beneath the Bay of Bengal (age ~ 140 Ma) has subsided at a significantly faster rate than the younger lithosphere beneath the Arabian Sea (age ~ 60 Ma). This differential subsidence has generated westward sub-lithospheric flows beneath the Indian Peninsula, interacting with east-directed mantle flows originating from regions below the Arabian lithosphere. This interaction has resulted in a localized mantle upwelling at the Western IP margin, contributing to the Western Ghats Escarpment (WGE) formation. Furthermore, we examine spatial variations in sub-lithospheric flow patterns to account for the increasing θ towards the south. Our findings suggest that the eastward topographic tilt of the IP is predominantly influenced by sub-lithospheric mantle dynamics, driven by lithospheric density contrasts between the Bay of Bengal and the Arabian Sea. This study provides valuable insights into the drainage patterns in IP.