Earthquake-Induced Liquefaction Features in the Quaternary Sediments of Zanskar River Valley, Leh-Ladakh Region, India

Well-preserved liquidation and fluidisation structures have been identified as most likely induced by liquefaction within the Quaternary fluvio-glacial and lacustrine successions of the Zanskar River valley (Leh-Ladakh, NW Himalaya). These features include a prominent gravel-filled clastic dyke intruding fluvioglacial deposits, which is interpreted as the key seismogenic structure. The dyke is systematically associated with fluidised or liquefied mud intrusions (sill-dyke), a variety of Soft-Sediment Deformation Structures (SSDS), and stratal displacement in the form of medium-scale faults. The observed SSDS comprise flame structures, ball-and-pillow structures, convolute and wavy lamination, and disrupted bedding. The vertical clastic dyke tapers upward and thickens downward, attaining a height of ~10 m and a basal width of ~1.3 m, with its upper part truncated. In sectional view, the fluidised mud displays upward-branching geometries both along and across the dyke margin, indicating forceful injection during rapid sediment liquefaction. Geological field evidence supports the interpretation that a strong seismic event triggered liquefaction and sediment mobilisation within this fluvio-glacio-lacustrine depositional system. Field relationships further suggest that the distribution and morphology of the deformation features were primarily controlled by sedimentary properties rather than pre-existing joints, fractures, or smallscale faults. The scale and abundance of these structures suggest that they were formed by a significant palaeo-earthquake rather than localised depositional or post-depositional processes. The combined evidence indicates that the observed features are produced by fluidisation and liquidation, and may have been induced by seismically driven liquefaction. These findings provide important insights into the long-term seismic behaviour of the Ladakh segment of the Himalaya, where instrumental and historical seismic records remain limited.