Systematics, age, paleoecology and paleobiogeography of Middle to Late Jurassic benthic foraminiferal assemblages from Jumara Dome, Kutch, Gujarat, India

Abstract

The studied section of the Patcham-Chari formations of Middle to Upper Jurassic rocks exposed at Jumara Dome, Kutch Basin, Gujarat, India yielded rich foraminiferal assemblages comprising 104 species, of which 49 are reported for the first time from the Indian region. The foraminiferal species are systematically described and illustratedwith the help of SEMimaging. The foraminiferal assemblages are used to interpret the age, paleoecology, and paleobiogeography. Although most of the foraminiferal species are rather long ranging, on the basis of a large number of species characteristic of the Bathonian, Callovian and Oxfordian, globally as well as in the Indian region, a Bathonian to Oxfordian age is assigned to the studied sequence. Based on the dominance of the suborder Lagenina, superfamily Nodosariacea, family Vaginulinidiae, calcareous hyaline forms, the genus Lenticulina, high Fisher’s diversity index, morphogroup J2, shallow infaunal life habit, detrivores, bacterial scavengers, and omnivores feeding strategy in the assemblages, a shallow water, near shore, open marine environment ranging from mid- to outer shelf with normal salinity and normal to well-oxygenated waters with high nutrient influx is interpreted for the studied assemblages. The Middle to Late Jurassic Jumara foraminiferal assemblages are assigned to a separate province of the Antiboreal Realm, the Indo-East African Province, located at the southern margin of the Tethyan Realm and transitional between the Tethyan and the Antiboreal realms.