3D Lithosphere density structure of southern Indian shield from joint inversion of gravity, geoid and topography data

• 3D lithospheric density structure of the southern Indian shield from joint inversion of gravity, geoid and topography data.
• Relatively thick lithosphere in Dharwar craton and Northen Block of the Southern Granulite Terrain.
• Proterozoic lithospheric root possibly exists today beneath the region.
• An unusually thinned lithosphere in the Southern Block of the Southern Granulite Terrain and adjoining Sri Lanka.
• The lithospheric root possibly modified due to Pan-African thermal perturbation and stretching due to the Gondwana breakup in the southern part.

We present the 3D crustal and lithospheric structure and crustal average density distribution of southern Indian shield (south of 18°N), Sri Lanka and adjoining oceans. The model is based on the assumption of local isostatic equilibrium and is derived from joint inversion of free air gravity and geoid anomalies and topography data. The derived crustal thickness of 10–25 km in the oceanic region increases to 34–35 km along the coast. A crustal thickness of 34–38 km is obtained beneath the Eastern Dharwar Craton and 36–45 km beneath the Western Dharwar Craton and the Southern Granulite Terrain. Sri Lanka has a thinner crust of 30–35 km. The lithosphere–asthenosphere boundary is located at depths of 70–120 km under oceanic regions and ∼150–180 km below the Dharwar Craton and the Northern block of Southern Granulite Terrain. A notably thinned lithosphere of ∼130 km near Bangalore in the Eastern Dharwar Craton, ∼140 km beneath the Southern block of Southern Granulite Terrain and ∼130 km in Sri Lanka is observed. The thickness of the lithosphere (∼130 km) near Bangalore is inferred as the frozen in signature of a small fossil mantle plume and/or tectono-compositional effect of a rifted margin and a suture. Considerable stretching and/or convective removal of pristine lithosphere in the Southern block of Southern Granulite Terrain and adjoining Sri Lanka, before disappearing completely in the Archaean Northern block of Southern Granulite Terrain and Dharwar Craton, is suggested.