Earthquake induced soft sediment deformation structures in the Paleoproterozoic Vempalle Formation (Cuddapah basin, India)

Soft sediment deformation structures (SSDS) are preserved in a homogenous dolomudstone lithology of crinkly laminated and heterolithic facies of the Paleoproterozoic Vempalle Formation in the Cuddapah Basin. This basin was formed on the eroded basement rocks of the Eastern Dharwar Craton, India. Deformation structures preserved in this succession include combination of breccia and folds, intrastratal faults, cracks, and dikes belonging mostly to a brittle deformation regime associated with ductile imprints. Based on the observed SSDS, their lateral homogeneity and traceability, draping by undeformed strata, proximity of faults as well as apparent lack of storm signatures and gravity induced mass movement, these fine-grained deformed beds can be tentatively ascribed to a large to intermediate depth earthquake with Richter magnitude scale 4 and above, generated during reactivation of basement faults owing to plume related mantle activity. The occurrence of SSDS in the Vempalle Formation emphasizes the role of downwarping along pre-existing planes of weakness in the Archean basement in the evolution of the Cuddapah Basin, analogous to subsidence in present-day continental margin.