Investigation on Sedimentary and Depositional Environment Usage of Cretaceous in South-East of Golpayegan Region

Abstract

In this investigation, the facies and their usage in the environment of cretaceous rocks that crop out at 35 km south-east of Golpayegan is studied. The section with 811 m thickness is composed of compact, dark marly shale, shale dark sandstones, orbitolina-contained limestone, marly limestone and calcareous limestone of early cretaceous (Albian), and dark gray limestone marly limestone of late cretaceous ages. Field and microscopic (petrographic) studies lead to recognition of 7 carbonate and 2 clastic facies. Facies 1 (Bioclast lime mudstone) indicates medium open marine environments. Facies 2 (Bioclast wackestone). Facies 3 (Peloid wackestone), Facies 4 (Bioclast packstone), Facies 5 (Bioclast packstone), Facies 6 (Intraclast packstone) and Facies 7 (Lime mudstone) indicate shallow to medium (sub-tidal) inter-tidal and supra-tidal deposition. In some cases, such as Facies 8 (Lime mudstone) and Facies 9 (Sandstone) Facies refer to a clastic condition which has direct relationship with active tectonic periods. Meanwhile in normal cases, Facies 4, 5 and 6 Facies are representative of carbonate basin in shape of homoclinal ramp.