Nature of the crust along Kuppam-Palani geotransect (South India) from Gravity studies: Implications for Precambrian continental collision and delamination

Closely spaced 3000 gravity measurements around Kuppam-Palani geotransect indicate the presence of an ancient continental collision along the Moyar-Bhavani-Mettur shear zone and crustal delamination beneath the Palghat gap. Paired gravity anomaly along with the faulted contact, dip reversal in seismic reflectivity pattern, northward vergence of the southern domain and high pressure-temperature granulites exposed on the Shevaroy hills are characteristic features of crustal thrusting through a late Archaean continental collision along the Moyar-Bhavani-Mettur shear zone. A unified 2 1/2-D gravity model along the seismic line is consistent with a tectonic history in which the Eastern Dharwar craton has been transported beneath the Southern Granulite Terrain. The gravity modeling further defines a 10 km thick high-density (2.89 g/cm3) crustal body at 10-15 km depth and a Moho warped up to a depth of about 38 km beneath the Palghat gap. The high-density intrusive body together with the upwarped Moho signifies the crust-mantle interaction in the Palghat gap region. Late Archaean continental collision and subsequent delamination are suggested as the twin cause mechanism for the present day crustal configuration along the geotransect.