Year: 2015
Type: article
Abstract: Quantifying bedrock cooling history is crucial for understanding the long‐term landform evolution across passive margins and its control onto the sediment routing system. To constrain the low‐temperature cooling history and its relationships to the Phanerozoic tectonic events of southern Peninsular India, we present new apatite (U‐Th‐Sm)/He (AHe) analyses of 39 Precambrian basement samples. The new AHe ages range from 38.1 ± 6.8 to 364.2 ± 44.6 Ma: they are younger than 50 Ma in the Palghat Gap region and older than 200 Ma in the interior of the Deccan Plateau. Thermal modeling based on AHe data indicates enhanced cooling and exhumation in the interior of the Deccan Plateau by Permian‐Triassic times followed by gradual cooling up to the Present. This discrete episode of Permian‐Triassic cooling is associated with continental extension that preceded the Early Jurassic breakup of Gondwana. Bedrock cooling and exhumation on the southeastern and southern limits of the Deccan Plateau was likely accomplished by Late Cretaceous drainage reorganization. The distribution of old (>200 Ma) AHe ages over the >2600 m high Nilgiri Plateau reflects very low erosion/exhumation rates and adds to examples of long‐lived postorogenic topography. The relatively younger AHe ages from the ∼30 km wide low mountain pass (Palghat Gap) within the Western Ghat Mountains attest for intense Cenozoic erosion likely facilitated by the erodible lithological backbone of the Neoproterozoic shear zone. AHe ages across the western coastal plain challenge the widely hold notion of ∼3 km of post‐breakup isostatic rebound in response to erosion of the margin. Instead, the new AHe data are more compatible with less than 1–1.5 km of crustal denudation along the coastal strip.
DOI: 10.1002/2015gc005977
Language: English
Subfield: Geophysics
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W2177379802