Palaeoseismicity in relation to basin tectonics as revealed from soft-sediment deformation structures of the Lower Triassic Panchet formation, Raniganj basin (Damodar valley), eastern India

摘要

The Raniganj basin in the Damodar valley of eastern India is located within the riftogenic GondwanaMaster-Basin. The fluvio-lacustrine deposits of the Lower Triassic Panchet formation ofthe Damodar valley in the study area preserve various soft-sediment deformation structures suchas slump folds, convolute laminae, flame structures, dish-and-pillar structures, sandstone dykes,pseudonodules and syn-sedimentary faults. Although such soft-sediment deformation structuresmaybe formed by various processes, in the present area the association of these structures, theirrelation to the adjacent sedimentary rocks and the tectonic and depositional setting of the formationsuggest that these structures are seismogenic. Movements along the basin margin and theintra-basinal faults and resultant seismicity with moderate magnitude (2–5 on Richter scale) arethought to have been responsible for the soft-sediment deformations.