Middle Miocene (Chokrakian, Karaganian) depositional environments of the Eastern Paratethys Sea in the southern Caspian Basin (Mazandaran Province, northern Iran)

Abstract

We present a detailed description of the Middle Miocene (Chokrakian and Karaganian) depositional environments of the Eastern Paratethys Sea in the southern Caspian Basin. The Chokrakian comprises a 500-m-thick succession of marls and sandstones, termed herein Javarem Formation, which formed in coastal marine environments. The lower Javarem Fm. Developed in calm lagoonal settings, indicating frequent exposure under a predominantly dry climate and occasional formation of evaporites. The upper part of the Javarem Fm. Is characterized by mixed siliciclastic-carbonatic sediments with ooids of agitated, warm, hypersaline tidal shoals. Above follows the about 500-m-thick Vashi Formation, which is correlated with the Karaganian regional stage. The formation is characterized by an alternation of reddish marls with thick sandstones and gravel beds with terrestrial gastropods, ubiquitous pedogenetic features and occasional root horizons. The depositional environment is interpreted as a floodplain with gravelly channels of an arid to semiarid climate. The successions of the Javarem and Vashi formations capture the transition from the shallow marine Iranian shelf into the northern Iranian coastal plain around 13.8 Ma, following the onset of the Miocene Climate Transition and the coinciding global sea level drop around the Langhian/Serravallian boundary.

Graphical abstract