Abstract
The following ammonoid and nautiloid taxa are described for the first time from the Upper Triassic succession (Ekrasar Formation, Shemshak Group) of northern Alborz, Iran: Arcestes sp., Arcestes ( Pararcestes ?) sp., Thisbites cf. agricolae Mojsisovics, Stikinoceras cf. kerri Mc Learn, Giesbachites sp., Griesbachites cf. pseudomedleyanus Diener, Griesbachites cf. himalayanus Wang & He, and Proclydonautilus ? sp. Palaeobiogeographically, the studied ammonoids are Tethyan in character, and stratigraphically attributed to the lower Lower Norian ( Guembelites jandianus Zone, possibly also Malayites paulckei Zone). The biostratigraphic data of this study demonstrate the diachronous base of the Shemshak Group: it is older in the northern Alborz (lower Lower Norian), but younger in Central Iran and probably also in the southern Alborz (Middle Norian).
Published Version
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