Sandstone body architecture and stratigraphic trends in the Middle Siwalik Succession of the Jammu area, India

Abstract

Sedimentological analysis has been carried out on the coarsening upward Middle Siwalik Succession of the Jammu area, India. Major sandstone bodies are composed of several storeys, and are tens of metres thick, continuing along strike for tens of kilometers. These sandstone bodies are mostly multistoried, representing several channel fill events; few thin sandstone bodies are single channel fill events. The detailed facies architecture of three of these sandstone bodies is discussed.Vertical sediment variation over a 1450m thick succession was studied to document the changes. The 550m thick upper part of the succession has a greater proportion and thicker sandbodies than the underlying 900m of the succession. This is accompanied by coarser grain size and poorer representation of fine grained deposits in the upper part of the succession, as compared to lower part. In general, palaeocurrent trends show a gradual change from SSW in lower part to SSE in upper part, which may be due to a change in direction of slope. The probable explanations for these up-section variations are tectonic and climatic change.