Intracontinental thrusts and inclined transpression along eastern margin of the East Dharwar craton, India

Abstract

Recent works suggest Proterozoic plate convergence along the southeastern margin of India which led to amalgamation of the high grade Eastern Ghats belt (EGB) and adjoining fold-and-thrust belts to the East Dhrawar craton. Two major thrusts namely the Vellikonda thrust at the western margin of the Nellore Schist belt (NSB) and the Maidukuru thrust at the western margin of the Nallamalai fold belt (NFB) accommodate significant upper crustal shortening, which is indicated by juxtaposition of geological terranes with distinct tectonostratigraphy, varying deformation intensity, structural styles and metamorphic grade. Kinematic analysis of structures and fabric of the fault zone rocks in these intracontinental thrust zones and the hanging wall and footwall rocks suggest spatially heterogeneous partitioning of strain into various combinations of E-W shortening, top-to-west shear on stratum parallel subhorizontal detachments or on easterly dipping thrusts, and a strike slip component. Although relatively less prominent than the other two components of the strain triangle, non-orthogonal slickenfibres associated with flexural slip folds and mylonitic foliationstretching lineation orientation geometry within the arcuate NSB and NFB indicate left lateral strike slip subparallel to the overall N-S trend. On the whole an inclined transpression is inferred to have controlled the spatially heterogeneous development of thrust related fabric in the terrane between the Eastern Ghats belt south of the Godavari graben and the East Dharwar craton.

Inversion of calcite twin data, paleostress reconstruction and multiphase weak deformation in cratonic interior – Evidence from the Proterozoic Cuddapah basin, India

“…This late compressional regime (ESEeWNW s 3 ) is also evident from the development of calcite mylonites derived from the Narji Limestone (Kurnool Group) in the immediate footwall of the Maidukuru thrust in the western margin of the Nallamalai fold belt (e.g. Saha et al, 2010). Extensional reactivation is also common along the studied faults during later phases as evident from the NEeSW s 3 from one sample (30NPEV).…”

“…It has been argued elsewhere that while thrusting along the western margin of the NFB (Maidukuru thrust) has led to development of strong calcite caxis fabric in carbonate mylonites derived from the Narji Limestone, the quartzites do not show comparable crystallographic fabric (Chakraborti and Saha, 2009). However, older contractional deformation along the Vellikonda thrust front at the eastern margin led to quartz mylonites with type I cross girdle fabric (Saha et al, 2010). Thus, inversion of e-twin corroborates multiphase regional deformation, and a weak but recognizable imprint is present even in the western part of the Cuddapah basin, 50e100 km west of the Nallamalai thrust front.…”

“…Several authors in recent years have suggested the possibility of more than one cycle of Proterozoic rifting, opening of sea and later convergence from records in the southern part of the Eastern Ghats, Prakasam alkaline province, Nellore-Khammam schist belt (NSB) and the Nallamalai fold belt (NFB), as well as those from the intracratonic basins further west of the EGB and other fold-and-thrust belts (Saha, 2004;Leelanandam et al, 2006;Vijaya Kumar and Leelanandam, 2008;Saha et al, 2010;Ravikant, 2010;Henderson et al, 2014;Saha and Patranabis-Deb, 2014;Saha et al, 2015). Although, the high grade terrains of the Eastern Ghats and adjoining fold-andthrust belts are important in linking India with other Gondwana fragments in the Proterozoic, the intracratonic basins provide important clues in sea level fluctuations which may be influenced (Tripathy and Saha, 2013).…”

“…Henderson et al, 2014). Post-depositional deformation in the Kurnool sub-basin is reported to be due to the thrusting of the NFB and strike-slip reactivation along faults like Gani-Kalva and Kona faults (Saha, 2002;Tripathy and Saha, 2008, 2013Saha et al, 2010). Such activities at the craton margins are expected to leave imprints in the basins in the cratonic interior, as in the case of the Cuddapah basin in the Eastern Dharwar craton (Tripathy and Saha, 2013).…”

Dismembered ophiolites in Paleoproterozoic nappe complexes of Kandra and Gurramkonda, South India

“…1). The belt is accreted to the southeastern margin of Eastern Dharwar craton along the Vellikonda thrust front (Venkatakrishnan and Dotiwala, 1987), which has been interpreted as a major intracontinental thrust (Saha, 2004;Saha et al, 2010). The NSB is marked by multiple deformation and low greenschist facies to upper amphibolite facies metamorphism across a 35-70 km wide belt (Ramam and Murty, 1997;Moeen, 1998;Saha, 2004).…”