Nature of the crust below the Southern Granulite Terrain (SGT) of Peninsular India across the Bavali shear zone based on analysis of gravity data

The Cambrian collisional suture of Gondwana in southern India: A geophysical appraisal

“…Gravity studies in 2000s have derived inputs from other studies like DSS to model the observed gravity anomalies within the PCSZ region (Singh et al, 2003) or used velocity-density relations for densities (Mishra et al, 2006;. For other gravity studies (Radhakrishna et al, 2003;Ajayakumar et al, 2006) support from DSS and/or MT were not available. Models derived from seismic refraction studies added more ambiguities to our understanding in PCSZ region and moreover the reflection studies across the PCSZ are markedly "noisy".…”

“…Another study identified a denser lower crust (2.85 gm/cm 3 ) with Moho depth ranging from 36 to 41 km (Ajayakumar et al, 2006). Excluding the earlier model by Singh et al (2003), all the other models (Radhakrishna et al, 2003;Ajayakumar et al, 2006;Mishra et al, 2006; show that the density of mid-lower crustal layers is more than about 2.75 gm/cm 3 for PCSZ and adjoining areas, suggesting relatively high density material beneath this zone.…”

“…Gravity modeling studies carried out to the north of PCSZ in the region west of Coimbatore indicate the presence of a 38 km thick crust with a high density mass of 2.98 gm/cm 3 at its base (Radhakrishna et al, 2003). The gravity studies south of PCSZ in the region west of Kodaikanal show that the upper layer is characterized by exhumed lower crustal rocks (2.76 gm/cm 3 ) and is almost homogeneous.…”

“…One of the additional inputs is the inferred change in lithology at around 22 km depth from the aeromagnetic anomaly map of the southern Indian Shied and adjoining regions (Rajaram et al, 2003). The flat layers with thicknesses of 15, 7 and 20 km and with crustal densities of 2.72, 2.76 and 2.88 gm/cm 3 have been taken based on the published results (see Radhakrishna et al, 2003) from the Bavali shear zone region near Gudalur-proximal to the present study area. A high density body (3.15 gm/cm 3 ) is considered to explain the conducting structure (shown in MT model, Fig.…”

Tectonic Classification of Dharwar Craton, INDIA.BASED on Inversion of Regional Bouguer Gravity.

“…The observed throws for the faulted blocks are 5 km along F-I, 6km along F-II, along F-III and 5 km along F-IV. (TABLE-I) Several plate tectonic models have been proposed for the evolution of the Dharwar craton, Naqvi, Manikyamba and associated of NGRI (Naqvi,2005), Kaila et al (1979) believed the Chitradurga thrust boundary to be the boundary between the eastern and western Dharwars, Chadwick et al (1989 & 1992) suggest that the lower and upper Chitradurga subgroups indicate an active continental margin or micro continental arc while Radhakrishna andNaqvi (1986,1985) suggest that the linear Chitardurga belt is possibly an Achaean suture generated as a result of collision tectonics and closure of oceanic basin between the juvenile continental blocks. However it is felt that this is extremely unlikely as the CT is not a deep seated fault, extending as it does only to the gneissic basement.…”