ABSTRACT
Sediments exposed to atmosphere are likely to be eroded soon after their deposition by various natural agencies. For preservation in the geological record it is essential that the sediments be pushed below the base level of erosion. The preservation potential of a deposit is determined by the rate of subsidence of the area of deposition vis-à-vis the rate of sedimentation. The areas of the earth’s crust which sink rapidly to allow preservation of a thick sediment load are called basins. Basins occupy large areas measuring thousands of square kilometres. Thinning of sediment layers towards the basin fringe is a sure indication of subsidence concomitant with sedimentation. In modern tectonic parlance a basin is a ‘prism of rock forming a thick sedimentary succession’ (Dickinson 1974). A model for basin evolution must explain, not only the mechanism of initiation of a depression in the earth’s crust but also the process of uplifting of the adjacent areas, in order to provide a source for the sediment fill.
