NORIAN AMMONOIDS FROM THE NAYBAND FORMATION (IRAN) AND THEIR BEARING ON LATE TRIASSIC SEDIMENTARY AND GEODYNAMIC HISTORY OF THE IRAN PLATE

Autor(en)

Leopold Krystyn, Marco Balini, BABAK SEPEHRIANNASAB AGHABABALOU, Vachik Hairapetian

Abstrakt

A Middle Norian (Alaunian 2) ammonoid assemblage from north of Esfahan (Central Iran) is described and chronostratigraphically evaluated. Formerly known as Distichites fauna, it represents a geographically widely distributed and stratigraphically important fossil level in the lower part of the Upper Triassic Nayband Formation. The new distichitid ammonoid genus Mesodistichites with the new species M. evolutus are introduced; additional faunal members are Noridiscites nodosus n. sp. and the leiostracean Stenarcestes diogenis and Pinacoceras cf. imperator.

The Nayband Formation of the Esfahan region, belonging to the Zefreh-Soh Facies, is lithostratigraphically emended to contain three formally introduced members (Parsefid, Venher and Niazmargh members), which are all of Norian age, whereas Rhaetian sediments are missing. These members are correlated with Norian lithostratigraphic units of the type sequence of the formation in Nayband, eastern Iran. Integration of all Iranian Nayband data allows the recognition of three 3rd order sequences within this formation and the proof of a major pre- or syn-Jurassic un-conformity across Central Iran and the Central-East Iranian Microcontinent (CEIM) related to the Main-Cimmerian event. Because of the latter and of major lithostratigraphic and facial differences, we propose to exclude the Nayband Formation from the Shemshak Group. A careful review of the available biostratigraphic data from northern and southern Iran let us further assume that the collision of the Iran Plate with Eurasia occurred in the later Early Carnian and was concurrent to the onset of the Carnian Humid Episode.

Organisation(en)

Institut für Paläontologie

Externe Organisation(en)

Islamic Azad University , Università degli Studi di Milano-Bicocca

Journal

Rivista Italiana di Paleontologia e Stratigrafia

Band

125

Seiten

231-247

Anzahl der Seiten

17

ISSN

0035-6883

Publikationsdatum

03-2019

Peer-reviewed

Ja

ÖFOS 2012

105118 Paläontologie

Schlagwörter

ASJC Scopus Sachgebiete

Geology, Palaeontology, Stratigraphy

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/591c6b60-f9ff-40f3-b5b8-a237371134ff