محيط رسوب گذاري و چينه نگاري سكانسي نهشته هاي پرمين در برش لب نسار (البرز شرقي

Depositional Environment and Sequence Stratigraphy of the Permian Deposits in Labnesar Section (Eastern Alborz)

The Permian succession in Labnesar section (Eastern Alborz) is composed of Middle Permian Ruteh and Upper Permian Nesen formations. These sediments, which show characteristics of marine to continental environments, were deposited in landward margins of the Paleotethys Ocean. Based on sedimentological characteristics, four depositional sequences were identified in the studied area. The first and second depositional sequences, which belong to the Ruteh Formation, show mixed siliciclastic-carbonate nature, whereas the third and fourth depositional sequences (comprising Nesen Formation) have terrigenous nature. The supersequence containing the Permian deposits is correlated to the Middle Absaroka (Transpecos) supersequence worldwide. Deposition of the supersequence was begun by Gondwanalandʹs deglaciation and global sea level rise in the Middle Permian and lasted to the Upper Permian. Global sea level fall at the end of Permian resulted in termination of deposition and initiation of a widespread unconformity at the Permian-Triassic boundary.