DEPOSITIONAL ENVIRONMENT OF INTERTRAPPEAN AND INTRATRAPPEAN BEDS OF THE ANJAR AREA, KACHCHH DISTRICT, INDIA: FORAMINIFERAL EVIDENCE

摘要

The intertrappeans associated with the Deccan volcanics of Jhilmili and Rajahmundri were reported to be marine, but the Anjar intertrappeans were previously advocated to have deposition in lacustrine or freshwater environment. The present investigation carried out on 26 samples collected from infratrappean, intertrappean and intratrappeans beds in and around Viri village, Anjar area, Kachchh district, India. The infratrappean (L-1), intratrappeans at the bottom as well as on the top (L-2 and L-6) are considered non-marine in origin as no foraminifera are recorded within these beds. Samples from the central portion of the area documented foraminiferal population which was not described earlier. Foraminiferal assemblages consisting of mainly Rotalia, Elphidium, Quinqueloculina, Nonion group of species within the intermediate intertrappean and intratrappeans (L-3 to L-5) are inferred to be deposited under shallow marine or ocean connected lacustrine environment. Presence of siliciclastic grains, rock-fragments, peloids and bioclasts also clearly indicate shallow water deposition. Increased abundance of Nonion spp., Quinqueloculina spp. as well as presence of planktic foraminifera (Pseudogloborotalia ranikotensis and Globigerina triloculinoides) within the intertrappean bed (L-3) is suggestive of relatively higher water depth at the site during deposition. Changes in deposition environments from non-marine to marine and finally non-marine sequence from older to younger indicate events of marine transgression followed by a regression phase.