Wave-dominated Shoreline Sediments in Early Cretaceous Surajdeval Formation, Saurashtra Basin, Gujarat Western India

Abdullah Khan, M. Aslam, Ebadur Rahman

The Early Cretaceous Surajdeval Formation of the Dhrangadhra group consists of the following three major facies: 1) a sand dominated facies (S), characterized by hummocky cross-stratification, planar and trough cross-bedding (Sp, St), and swaley cross stratification (SCS). 2) the hetro lithic facies (H) characterized by shatter red mudstone and fine-to very fine grained sandstone / red siltstone, exhibiting parallel and low-angle cross-laminations including symmetrical and interference ripples; 3) sand matrix-supported conglomerate/pebbly facies (Cg-S) displaying an alternation of coarse (50mm), medium to fine (<10-20 mm) pebbles in successive beds, and couplets of crudely graded conglomerate.

      The sedimentary facies and structures of the Surajdeval Formation reflect deposition by wave, and tide dominated events. Parallel-laminated and fine-grained sandstones are deposited in response to decrease incompetency and capacity of the flow.

      The conglomerates and couplets with sandstone may be the product of longshore deposits. Mudstone may have accumulated in protected lagoonal environment. Paleocurrent indicators, such as cross-bedding and pebble fabric show orientation toward south-south-west, and north-north-west, and may be attributed to ebb tidal (onshore), and those exhibiting north-north-west orientation to flood tidal/ longshore (off-shore) currents. Thus, the sedimentological features of the Surajdeval Formation suggest that wave tides and storm processes were involved during its deposition.