Facies features and paleoenvironmental reconstruction of the Early to Middle Devonian syn-rift volcano-sedimentary succession (Padeha Formation) in the Eastern-Alborz Mountains, NE Iran

Abstract

The Padeha Formation in the Eastern-Alborz Mountains (northeast Iran) is an Early to Middle Devonian syn-rift succession. Siliciclastic rocks (conglomerates, sandstones, mudstones, and red paleosols) to non-marine carbonates (yellowish calcretes, dolocretes, stromatolites, and sandy bivalve packstone) associated with volcaniclastic rocks (basalts or andesites and tuffs) are present in this succession. Facies analysis led to the recognition of three facies associations that are deposited in three terrestrial environments (alluvial fan, distal fan, and palustrine/lacustrine). Its sedimentary fill pattern and association with mafic volcaniclastic rocks indicate that this formation is related to the initial phase of a rift basin (intracratonic rift). Paleosols of this formation are good indicators for recognition of paleoenvironmental factors (climatic changes from semi-arid to sub-humid with annual fluctuation, small and short gross-like vegetation cover, subaerial exposure, very shallow lake, volcanic source rocks, and early meteoric diagenesis).