Application of grain-size statistics, lithofacies and architectural element in determining depositional environment of Kashkan Formation in Merk watershed, Kermanshah

摘要

Kashkan Formation is located in Merk watershed in the southeast of Kermanshah, Iran, at a distance of 35 km. The age of the studied formation ranges from upper Paleocene to middle Eocene. This formation is located between two shallow-environment carbonated formations (Teleh-Zang Formation at the bottom and Shahbazan Formation at the top). While there is no Teleh-Zang Formation (like the study area), Kashkan Formation lies above Amiran Formation. Regarded also as a forest, this formation includes clay, silt and sandstone. Field and microscopic studies reflect two sandstone (chert arenite and lithic arenite) and siltstone petrofacies. In this study, seven lithofacies (Gm, Sm, St, Sr, Fm, Fl and P) and four architectural elements (CH, CS, FF and OF) were identified in two sections. The detailed grain-size analysis was used as a vital sedimentological tool to unravel the hydrodynamic conditions, mode of transportation and deposition of detrital sediments. Twenty samples from Kashkan Formation were investigated. Parameters of grain statistics and bivariate analysis were used to reveal the depositional processes, sedimentation mechanisms, hydrodynamic energy conditions and to discriminate different depositional environments. The results showed that the depositional environment of Kashkan Formation is braided river with sedimentary load of sand and silt classified as Bijou Creek Type.