Deformation of the Paleoproterozoic Lower Vindhyan Group in Central India: synsedimentary origin or associated with the Mesoproterozoic convergence between the Bundelkhand and Bastar Cratons?

Abstract The Central Indian Tectonic Zone (CITZ) formed during the Mesoproterozoic north-south collision between the Bundelkhand and Bastar Cratons. The origin of the deformation of the Late-Paleoproterozoic Lower Vindhyan Group (LVG), which occurs in the sedimentary basin adjacent to and north of the CITZ, is debated, with previous researchers supporting synsedimentary processes. To investigate the possibility of a collisional origin, we collected and analysed litho-structural data from the LVG and the Mid-Paleoproterozoic Mahakoshal Supracrustal belt (MSB), which lies within the CITZ. We report, for the first time, diverse structures from the LVG, such as various types of buckle folds including kink-folds, reverse faults and, most importantly, 5–20 meters long outcrops of pop-up structures, which are commonly encountered in fold-thrust belts. However, the adjacent MSB showes relatively complex polyphase deformation with three major deformation stages that produced: (i) E-W-trending regional foliation and diversely oriented folds ( D1 ), (ii) E-W oriented steep folds associated with a large-scale shear zone along the Son-Narmada South Fault ( D2 ) and (iii) local cross-folds ( D3 ). Based on our field observations in the LVG and the MSB, we additionally propose and substantiate, through geological cross-sections and a kinematic model, that the LVG deformed between the D3 and the deposition of the Upper Vindhyan Group. Unlike previous studies, which attributed the deformation structures of the LVG to seismic or soft-sediment processes, our findings confirm that the Mesoproterozoic collision along the CITZ deformed the LVG as the deformation front, aided by detachment folding, propagated into it.