This chapter covers lithofacies paleogeography, a data-intensive field that includes sedimentary facies interpretation and compilation. Lithofacies analysis involves the description and classification of sediments, which is usually achieved here by using (Miall in Earth-Sci Rev 22:261–308, 1985) facies model to evaluate sedimentary processes and depositional settings. A range of main sedimentary structures (sandstone, mudstone and conglomerate make up the majority of the Siwalik group of rocks) can be found mainly in sandstones, which have fine, medium or coarse grains. Conglomerates support a localized debris flow type that is clast-supported by a matrix. Mudstones have burrows and impressions of plant leaves and stems. They are essentially non-laminated and bioturbated. A classification of the litho-succession based on various lithofacies has been performed throughout the current investigation, and they have ultimately been categorized into several fluvial facies associations. In the DSH foothills (between the Tista and Gish River valleys), five main facies associations (FA1 to FA5) are recognized based on lithocharacter, litho-association, grain size, primary sedimentary structures, thickness of layers, fossil content and sediment body architectures. The overall characteristics of the sedimentary deposits in the various FAs indicate that Lower Siwalik was deposited in a deltaic coastline meandering estuarine river system, Middle Siwalik was deposited in a braided river system with periodic flooding, and Upper Siwalik was deposited in an over alluvial fan condition with periodic rising of provenance area.