Microfauna, Palynomorphs, and Biostratigraphy of the Upper Bajocian Strenoceras niortense Zone (Middle Jurassic) of the Kuban River Basin, Northern Caucasus

Abstract

The results of the study of microfossils of the Strenoceras niortense Zone of the Upper Bajocian of Karachay-Cherkessian Republic are presented. The zone is represented mainly by dark gray silty-sandy clays, with nodules scattered in the stratum, often forming interbeds, and belongs to the lower part of the upper subformation of the Djangura Formation. The systematic composition and distribution of foraminifera, ostracods, dinoflagellate cysts, and myospores in the section have been established. The volume of biostratigraphic subdivisions for foraminifera, ostracods, and dinocysts has been specified; they were compared with the ammonite scale. According to benthic foraminifers, these are beds with Ophthalmidium caucasicum, comparable with the entire Niortense Zone and most of the Garantiana Zone. The beds with Globuligerina dagestanica established by planktonic foraminifera are compared with the entire studied interval from the Niortense zone to the Lower Bathonian, inclusive. In the middle-upper part of the Niortense Zone (Rostovtsevi and Baculatum Subzones), beds with ostracods Palaeocytheridea (Malzevia) subtilis were established for the first time. Beds with dinocysts Carpathodinium predae, Rhynchodiniopsis? regalis, Meiourogonyaulax valensii are understood within the volume of the Niortense and Garantiana Zones and the lower part of the Parkinsoni zone, inclusive. Images of characteristic taxa of microfauna and dinocysts are given.