Neorbitolinopsis conica (Matsumaru in Matsumaru and Furusawa, 2007) comb. nov., a Lower Cretaceous marker from the Orbitolina Limestone of Central Iran

Abstract

New biostratigraphic data about the Lower Cretaceous “Orbitolina limestone” (Shah Kuh Formation) that transgressively overlies the Anarak Metamorphic Complex in Central Iran is provided from a section near Anarak. The presence of the Praeorbitolina biozone at the base documents an early Aptian age. In the late Aptian, the “Orbitolina limestone” is topped by an emersion surface. This level/event might correspond to the beginning of the supra-regional late Aptian sea-level lowstand. It is followed by carbonates ascribed to the Albian Bazyab Formation, although no precise age indicator has been observed. From the Shah Kuh Formation, the previously unrecorded species Paleodictyoconus conica (rect. conicus) Matsumaru in Matsumaru and Furusawa, 2007 (early-late Aptian of Japan) is described and taxonomically revised as Neorbitolinopsis conica (Matsumaru) comb. nov. A literature review (including other records from Iran under different names or in open nomenclature) leads to the conclusion that Neorbitolinopsis conica represents a marker for the upper Bedoulian to Gargasian stratigraphic interval in this area. The studied section also provides the first record of Palorbitolinoides Cherchi & Schroeder from the early Aptian of Central Iran.