Breakup of Gondwanaland and the Jurassic record of the Kachchh basin, Gujarat, western India

The pericratonic Kachchh basin of Gujarat, western India, hosts a succession dominated by siliciclastics punctuated by oolitic limestone horizons. The two horizons occur in distinct time frames, the older in the Bathonian and the younger in the Oxfordian, The younger horizon the Dhosa Oolite, Member of the Jumara Formation forms an important lithostratigraphic marker horizon. These two horizons are re-interpreted as ironstone horizons based on iron sequestration observed at field outcrop and petrographic scale. It ii suggested that the iron content in the ironstones is on account of hydrothermalplumes of a magnitude similar to the infrequent Event hydrothermal plumes observed in the case of Juan de Fuca ridge off the western coast of Canada. Therefore the ironstones could represent two phases of increased sea-floor spreading activity-related to the breakup of Gondwanaland. The older ironstone; known as Golden Oolite documents the formation of a mid-oceanic ridge system after a period of continental stretching, while the Dhosa Oolite is the manifestation of the migration of Greater India as a discrete continental landmass, from Gondwanaland.