Abstract
Plateaus, located far away from the plate boundaries, play an important role in understanding the deep-rooted geological processes responsible for the epeirogenic uplift and dynamics of the plate interior. The Karnataka plateau located in the Dharwar craton, southern India, is a classic example for the plateau uplift. It is explored using orthogonal deep crustal seismic reflection studies, and a mechanism for the epeirogenic uplift is suggested. A pseudo three-dimensional crustal structure derived from these studies suggests a regionally extensive 10 km thick magmatic underplating in the region. It is further constrained from active-source refraction and passive-source seismological data. We interpret the Marion and Reunion mantle plume activities during 88 Ma and 65 Ma on the western part of Dharwar craton are responsible for the magmatic underplating, which caused epeirogenic uplift. Flexural isostasy related to the onshore denudational unloading and offshore sediment loading is also responsible for the persisting uplift in the region. Plate boundary forces are found to be contributing to the plateau uplift. The present study provides a relationship between the mantle plumes, rifting, development of continental margins, plateau uplift, and denudational isostasy. Combination of exogenic and endogenic processes are responsible for the plateau uplift in the region.
Highlights
Plateaus, located far away from the plate boundaries, play an important role in understanding the deep-rooted geological processes responsible for the epeirogenic uplift and dynamics of the plate interior
Especially those away from the plate margins, provide important inputs to understand the interplate geo-dynamics because of the involvement of deep-rooted geological processes that are different from the active subduction environment
The pseudo-3-D crustal structure derived from orthogonal profiles identified 10 km thick subhorizontal lowercrustal fabric associated with a high-velocity (7.1 km/s) layer which is interpreted as magmatic underplating
Summary
Plateaus, located far away from the plate boundaries, play an important role in understanding the deep-rooted geological processes responsible for the epeirogenic uplift and dynamics of the plate interior. Some of them are related to convergent and divergent plate margins, and others are far away from these margins (e.g., Tibet and Shillong-convergent, Ethiopia-divergent, Colorado-intraplate) Plateau uplifts, especially those away from the plate margins, provide important inputs to understand the interplate geo-dynamics because of the involvement of deep-rooted geological processes that are different from the active subduction environment. Important among the possible mechanisms responsible for plateau uplift are physical thickening of crust, thermal expansion and thinning of the lithosphere[1,2], phase change in the lithosphere (basalt-eclogite, spinel-olivine), delamination of the mantle lithosphere[3], magmatic underplating[4] and flexural response to denudation[5,6] Some of these processes occur during rifting and operate only for a short period and thereby it can’t explain the post-rift u plift[7]. This plateau, a part of the elevated region, is contiguous with the Deccan plateau (Fig. 2, DP) located to its north, which together occupies an area of more than 400,000 sq. k m10
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