Lithospheric structure of the Dharwar Craton (India) from joint analysis of gravity, topography, and teleseismic travel-time residuals

Abstract

• Effective elastic thickness of the Dharwar Craton varies between 12 and 35 km. • Both crust and lithospheric mantle contribute in supporting topography load. • Western Dharwar craton is thicker than the eastern Dharwar craton. • A Jelly-Sandwich type lithospheric architecture is possibly applicable in the Dharwar craton. The evolution and persistence of an uplifted surface along a passive continental margin is a long-standing enigma. The long-term vertical strains generated by such surface topographic loads have to be supported and maintained by the lithosphere's elastic strength. We estimate the lithospheric strength indicated by its effective elastic thickness (Te) and associated regional lithospheric structure along an ENE-WSW profile across the Dharwar craton-western Ghats (elevation ∼1200 m). We employ a joint analysis of teleseismic travel time residuals, Bouguer gravity, and topographic data. Our results suggest the topographic load of the Western Ghats is supported by both the Archean Dharwar crust and the lithospheric mantle (∼40 %), and indicate the possibility of a Jelly Sandwich type of rheology operating in this region. However, towards the eastern section of the profile, where the terrain flattens out, the contribution of the lithospheric mantle in maintaining the topography is observed to be uncertain due to resolvability of the method. Further, we infer the presence of ∼20–30 km thicker lithosphere beneath the western Dharwar craton (WDC) than the eastern Dharwar craton (EDC). The obtained Te values varies from ∼12 km (in the west of the WDC) to ∼32 km (towards the east of the EDC). These Te estimates are in agreement with previous studies from the region and are much lower than those for the more recent geological terrains in the subcontinent, such as the Gangetic plains and the Himalaya orogen.