Deformation pattern and evolution of the structures in the Penganga Group, the Pranhita–Godavari Valley, India: probable effects of Grenvillian movement on a Mesoproterozoic basin

Abstract

Recent studies reveal imprints of tectonic deformation in the Mesoproterozoic rocks of the Pranhita–Godavari (P–G) Valley, India. Outcrop-scale structures that record a progressive sequence of deformation can thus be used to clarify the kinematic evolution of the Penganga Group, a Mesoproterozoic succession in the northern and central parts along the SW marginal Proterozoic belt of the PG Valley. Overprinting relationships among the structures in the northern part indicate three distinct structural stages: (1) layer-parallel shortening, (2) thrusting and folding in combination, and (3) extensional joint and fracture opening. The former two stages are explained in the framework of a progressive deformation model. The extensional structures were produced during exhumation. Similar structures are also developed in the central part of the SW belt of the PG Valley, though the two areas slightly differ in the overall pattern of deformation. The geometry of the progressive deformation structures from both regions of the belt suggests that they were produced under a regime of NE–SW/ENE–WSW directed regional compression. The deformation in the Proterozoic basin is possibly related to the Grenvillian orogeny recorded in the Eastern Ghats mobile belt, and may represent a small-scale Meso-Neoproterozoic convergence event.