Pdf: http://ajes.in/PDFs/08-2/13.%20Microfacies%20and%20depositional.pdf

The Kachchh Basin is a pericratonic rift basin situated at the western margin of the Indian plate. The Jumara Dome is one of the important exposures of Bathonian sediments among the Kachchh Mainland exposures. A rigorous facies analysis using the microfacies approach for the reconstruction of the depositional environment and setting of carbonate sedimentation with correlation of basin components had been lacking. Thus an important Kachchh Mainland outcrop of the Bathonian sediments (Jhurio Fm.) viz. the Jumara Dome was taken up for the present study. In accordance with the above-mentioned objectives detailed stratigraphical sections of the Jhurio Formation have been measured. Macrofacies were recorded for corroborating the microfacies data. Microfacies analysis has been carried out by studying thinsections of rock samples under the microscope with the aim to interpret the depositional environment and setting. The study helped in the reconstruction of the depositional environment and setting at the Bathonian times represented by the Jhurio Fm. The Jhurio Fm. at the Jumara dome is characterized by well-bedded limestone-marl/marlstone alternations and massive limestones (packstones and grainstones). The sections have several units where the limestone show nodular feature. Various microfacies types are present in the Jhurio Fm. at the Jumara dome. The MF types are associated into two MF associations at the dome. A carbonate ramp setting seems to have been prevalent at the time of sedimentation of the carbonates during the Bathonian. In general, the depositional environment seems to have been a marine, open sea, mid to outer (deep) ramp environment. Depositional environment was largely low energy just below storm wave base which had seen phases of slight influence of storm events. Reworked sediments of the transgressive phase witnessed relatively higher energy depositional environment.