Original paper

Depositional environments and sequence stratigraphy of the fluvial Upper Red Formation (Miocene) in the Avaj area, Qazvin Province, Iran

Rafiei, Behrouz; Ghomi, Fatemeh Ahmadi; Shahkaram, Mehrdad

Abstract

The Miocene Upper Red Formation (URF) in the north of Avaj was deposited in a fluvial system under dry and warm climatic conditions. Amalgamated sandy braided, meandering and gravelly braided facies associations can be recognized in the lower, middle and upper parts of this formation, respectively. The Lowstand System Tract (LST) in the model comprises braided river deposits; the Transgressive Systems Tract (TST) and Highstand Systems Tract (HST) consist of mainly meandering river deposits. The studied formation consists of two sequences. The lower sequence consists of amalgamated sandstone of braided river origin and isolated sandstone of meandering river origin. The upper sequence comprises gravelly braided river deposits. Fining-upward trends in these deposits indicate decrease in fluvial energy. Gravelly braided river sediments immediately succeeding meandering deposits show sudden increase in fluvial energy, indicative of tectonic rejuvenation.

Keywords

fluvial strataupper red formationmioceneavaj areasequence stratigraphyiran