Sokolowia Horizon of the Ziarat Formation (Eastern Alborz, Iran): Biostratigraphic and Paleogeographic Implications

Abstract

The present study deals with molluscan accumulations of the Sokolowia horizon, which is a key-bed in the middle Eocene of the Kalateh section (Ziarat Formation, Eastern Alborz, Iran). The age of this “key horizon” is at-tributed to Bartonian based on presence of larger benthic foraminifera species such as Nummulites lyelli (D'Archiac & Haime), Orbitoclypeus zitteli (Checchia-Rispoli) and Asterocyclina stella stella (Gümbel) immediately below it. The paleogeographic distribution of Sokolowia occurrence from Tarim Basin in eastern Central Asia to the Transylvanian Basin in southeastern Europe indicates a middle Eocene seaway along the southern margin of an Eurasian epicontinental sea. In particular, the comparison of middle Paleogene sequences in different Central Asian regions reveals an apparent similarity between those basins pointing to their genetic relationship.

The bivalve-bearing carbonate platform on the east Tethys during the middle Eocene and its response to the Tethys transgression

“…Several authors also pointed out that Sokolowia lived in normal salinity conditions in a deeper part of the shallow water zone under the influence of wave action (e.g., Stenzel, 1971;Mészáros et al, 1987;Lan, 1997). Their thick-walled, heavy shells made them practically immovable by water turbulence at the sea bottom (Hadi et al, 2019). The individuals vary in size, and the genus and species are monotonous.…”