Reconstruction of Depositional Environment of Sarchahan Formation (Silurian) in the Persian Gulf

Abstract

Sarchahan Formation (Silurian) consists of shale and sandstone interbeds in the studied well in the Persian Gulf. Sedimentological characteristic of this formation is presented here for the first time. Based on petrographic studies and wire line logs studies, five petrofacies and three facies associations were identified in the Sarchahan Formation. Variations in facies association in combination with palynological studies represent that deposition of the Sarchahan Formation took place in different subenvironments of a delta environment from prodelta to delta plain. The lower part of the formation is represented by a high amount of black shale and higher total organic carbon values which are the result of deposition in the deeper parts of the basin. Meanwhile, the upper part is composed of sandstone and red mudstone which are the result of deposition in the shallower part of delta environment. Cementation, compaction and dissolution are the main diagenetic features which affected the Sarchahan Formation. Silica and sericite cements are the most abundant cement types in quartzarenite and subarkose petrofacies the development of which resulted in porosity reduction. The comparison with the Arabian plate, the deposition took place in a southward deepening basin into which sediments were introduced from the northern parts. .