In Late Triassic, rifting began between India and Africa during fragmentation of Gondwanaland (Biswas, 1982, 1991). The Jurassic-Cretaceous Sea transgressed into parts of western India (Krishnan, 1960) along with the coastal areas of East Africa, including Somalia, Kenya, Tanzania and Madagascar (Cannon et al. 1981). It coincided with the opening of Kachchh Basin to the north of uplifted Saurashtra Peninsula for the first time with the ingression of a shallow epicontinental Jurassic sea (Biswas, 1987).
The basin is considered an elongated extensional trough where up and down rifting lead to basin formation and sedimentation at first in the northern part (as the Jurassic of Kachchh) and later in the southern part (Early Cretaceous of Saurashtra/?Kachchh) (Casshyap and Aslam, 1992). These rift basins bounded by major faults/mega-lineaments (Biswas, 1982) are examples of a pericratonic composite rift system (Sengor et al. 1978). This system coincided with the eastern failed arm of triple -rift junction. The pericratonic rift system was developed in response to the extensional forces when the Indian plate ruptured from Somalia/ Madagascar/Oman and moved northward with the opening of Indian Ocean (Arabian Sea) to the west. Similar pericratonic failed rifts/grabens were also formed during plate separation in Jurassic and Early Cretaceous in other parts of Gondwanaland that had rapid accumulation of continental to marine clastics and/or calcareous sediments (Tankard et al. 1982).
During Middle to Upper Jurassic, India along with its adjoining regions of Afghanistan, Iran, Jordan, Egypt, Somalia, Ethiopia, and Malagasy, occupying the shallow water of the Indo-Malagasy or Indo-East African Gulf belonged to the Indo-East African Province (Talib and Gaur, 2008) (Fig. 10). During its evolution, the basin has also encountered a changing palaeoshoreline (Balagopal and Srivastava, 1975; Casshyap and Aslam, 1992) from north-south to dominantly northwest-southeast. There was a global rise in sea level which transgressed and deposited sediments during Oxfordian.
There are two major tectonic phases in the Mesozoic Kachchh Basin i.e, early rift phase and termination of this phase by failing of the rifting processes (Biswas, 1982). The sedimentation in Kachchh Basin corresponds to the early rift representing a transgressive succession interspersed by small cycles of transgression and regression (Osman and Mahender, 1997).
A discrete assemblage of lithofacies or its succession cannot be a characteristic to the failed rift and aulacogens (Miall, 1984). However, graben stage with transgressive or regressive shoreline can be described with the continental to shallow or deep marine, clastic or carbonate facies. Their energy conditions can be explained with the help of the facies encountered in the field. For example, the matrix- supported conglomerate and medium- to coarse -grained thick to thin laminated, friable soft to compact cross-bedded sandstone facies can be interpreted as high energy coastal deposits may be a stand-still period with low sediment supply within the transgressive phase. On the contrary, an agitated offshore setting rendered the deposition of the oolitic limestone facies. Deposition of the Ler Dome sequences took place in different ways. The channelized flows resulted in cross-beds and parallel laminated sandstones along with the un-channelized flows that deposited more or less high energy facies alternately in form of coarse/medium- to fine-grained sandstones and inter-bedded sequence of interbedded gypsiferous shale and sandstone/siltstone facies. The interbedded sequence may be an indication of frequent upheaval of the source area and frequent fluctuation of sea level.