Biostratigraphic partition of the Upper Jurassic and Lower Cretaceous (Oxfordian - Lower Berriasian) deposits of the Crimean Mountains for foraminiphers

Abstract

Introduction. Upper Jurassic and Lower Cretaceous deposits in the Crimean Mountains are widespread and are represented by all stages ‑ Oxfordian, Kimmeridgian, Tithonian, and Berriasian. These deposits have been unevenly studied. The most studied deposits are the Oxfordian, Tithonianian and Berriasian stages. The biostratigraphic division of the Upper Jurassic and Lower Cretaceous deposits of the Mountain Crimea is based on "Stratigraphic scheme of the Upper Jurassic and Lower Cretaceous deposits of the Mountain Crimea" 2013. Purpose. Detailed biostratigraphic devision of the Upper Jurassic and Lower Cretaceous (Oxfordian ‑ Lower Berriasian) of the Mountain Crimea as results of foraminiferal analysis. Results of the study. There are five foraminiferal complexes in sections that characterize Upper Jurassic (Lower Upper Oxfordian, Lower Kimmeridgian, Upper Tithonian) and Lower Cretaceous (Lower Berriasian) age. Analysis of foraminiferal complexes allowed us to establish biostratigraphical zones in each section: oxfordiana in the Lower Oxfordian Lenticulina quenstedti-Globuligerina; in the Upper Oxfordian Lenticulina russiensis-Epistomina uhligi; in the Upper Tithonian Anchispirocyclina lusitanica-Melathrokerion spirialis; in the Lower Berriasian (lower zone) Protopeneroplis ultragranulatus-Siphoninella antiqua and layers in the Lower Kimmeridgian with Epistomina praetatariensis-Globuligerina parva. Specified foraminiferal zones were traced by us in different structural-facial zones (zone Lenticulina quenstedti-Globuligerina oxfordiana ‑ in Sudak-Feodosia; zone Lenticulina russiensis-Epistomina uhligi ‑ in Ai-Petri-Babugansk and Sudak-Feodosia; strata layers with Epistomina praetatariensis-Globuligerina parva ‑ in Sudak-Feodosia; zone Anchispirocyclina lusitanica-Melathrokerion spirialis ‑ in Sukhorychensk-Baidar, Demerdzhi-Karabijskaya and Sudak-Feodosiya; the zone of Protopeneroplis ultragranulatus-Siphoninella antiqua in Demerdzhi-Karabijskaya and Sudak-Feodosiya). Characteristic features of each foraminiferа zone include a complex of species, disappearing species, and species that continue to exist, as well as particular features of the complexes. According to lithological peculiarities and paleontological characteristics, suite and sub suite are defined. Conclusions. As a result of the study, the biostratigraphic characteristics of the sections have been specified and the paleontological characteristics of the Upper Jurassic and Lower Cretaceous deposits of the Mountain Crimea have been supplemented.