Environmental interpretation and sequence stratigraphy of the Nazarkardeh Formation (Anisian) in Aghdarband area, NE Iran

Abstract

The Nazarkardeh Formation with of early Anisian age crops out in the Aghdarband erosional window in NE the northwestern part of Iran and is the second unit of the Aghdarband Group. The lower contact with the Sefidkuh Formation is gradational, while the upper contact with the Sina Formation is erosional. Three stratigraphic sections were measured with the following thicknesses: at Nazarkardeh (type locality 46.5 m), Kalbast 1 (23.5 m) and Kalbast 2 (28 m) and 80 samples were collected. Petrography studies led to the identification of 8 carbon ates and 2 pyroclastic lithofacies. Based on lithofacies analysis, this formation may have been deposited in a homocline carbonate ramp within a fore arc basin. Sequence stratigraphy analysis led to the recognition of a third order depositional sequence in all measured sections bounded by sequence boundaries type II at the base and type I at the top. The interpreted sea level curve in the study area can be correlated with the worldwide sea level curve, and regional subsidence led to the deposition of several small scale cycles. We hope this information can be used in the reconstruction of Triassic paleogeography of Iran and other parts of the world.