Stratigraphical Study of the Taft Formation in the Bohruk Area from Yazd Block, Central Iran

Abstract

The Taft Formation is exposed at the Bohruk area from Yazd Block in central Iran with 136 m thickness comprising three informal members which are named, in ascending stratigraphical order named Lower, Middle and Upper members. The Lower and Upper members consist of bioclastic carbonate rocks, whereas the Middle Member contains two sub-members: carbonate and siliciclastic carbonate rocks. Four patterns of facies are recognized on the basis of field observation and microscopic study. They are grainstone facies, siliciclastic-carbonate facies, intermediate facies (grainstone-wackestone/packstone facies) and foraminiferal-clastic wackestone/packstone facies. Based on the facies associations, three facies belts are presented for the first time. Therefore, this formation was deposited on a shallow carbonate platform from the inner platform to rimmed platform. The main fauna of the Taft Formation include Istriloculina eliptica (Iovcheva), Palorbitolina lenticularis (Blumenbach), Charentia cuvillieri Neumann, Everticyclammina hedbergi (Maync), Pseudocyclammina litus (Yokoyama), Melathrokerion valserinensis Bronnimann & Conrad, Nautiloculina oolithica Mohler, Glomospira urgoniana Arnaud Vanneau, Dicyclina schlumbergeri Munier-Chalmas, Derventina filipescui Neagu, Praechrysalidina infracretacea Luperto-Sinni, Pseudochoffatella cuvillieri Deloffre, Paracoskinolina sp., Textularia sp., and Lenticulina sp. Based on the foraminiferal distribution throughout the Taft Formation, two biozones like Istriloculina elliptica-Palorbitolina lenticularis zone and Glomospira urgoniana-Dicyclina schlumbergeri zone are recognized they and range from the Late Barremian to Early Albian in age.