Seismic origin of the soft-sediment deformation structures in the upper Palaeo-Mesoproterozoic Semri Group, Vindhyan Supergroup, Central India

Abstract

Soft-sediment deformation (SSD) structures are the syn-sedimentary structures that can form by seismic as well as non-seismic processes. The SSD structures commonly occur in the Semri Group of the Vindhyan Supergroup in the Kajrahat Limestone, Chopan Porcellanite and Rohtas Limestone formations, and the Glauconitic Sandstone Member. The SSD structures include, slump folds, kink bands, chevron folds, convolute beddings, contorted cross-beds, flame structures, pinch-and-swell structures, breccias, sagging structures, water-escape structures, and dykes of varying dimensions. The lagoonal and tidal depositional environments of the Kajarahat Limestone Formation (not the continental slope environment) lead to suggest that the SSD structures formed as a result of the seismic activities in them. The SSD structures of the Chopan Porcellanite Formation associated with rhyolite might have originated as a result of volcanic activities or seismicity, while those occurring in the Glauconitic Sandstone Member (Kheinjua Formation) adjacent to the Son Lineament might have formed as a tectonics-related seismicity. The convolute bedding with large lateral extent in the Rohtas Limestone Formation looks related to seismicity in the light of its deposition along the shelf. Thus, the upper Palaeo-Mesoproterozoic Semri Group, Vindhyan Supergroup represents varieties of the SSD structures formed mostly by seismic processes. These imply that the Central India was unstable and was a place for tectonically controlled seismic events during the upper Palaeo-Mesoproterozoic (1,700–1,600 Ma). © 2020 John Wiley & Sons Ltd