Soft Sediment Deformational Structures in the Lacustrine Deposits of Ziro Valley, Lesser Himalaya, Arunachal Pradesh

Soft sediment deformational structures of various types are preserved in the lacustrine deposits at Soro village of Ziro valley, Lesser Himalaya, Amnachal Pradesh. The structures that have been observed include sand dykes, flame structures, load casts, micro-folds, convolute and other complex structures. The affected sediments are predominantIy loosely packed cohesionless sands and silts due to change of state from grain supported to fluid supported matrix by application of external force; and are enclosed between two undeforrned layers. Earthquake induced liquefaction is proposed for the formation of such structures taking into consideration the geodynamic conditions of the region.