Middle Aptian biostratigraphy and ammonoids of the Northern Caucasus and Transcaspia

Аннотация

The Middle Aptian deposits of the central and eastern regions of the Northern Caucasus and Transcaspia (Turkmenistan) are described and discussed, including the history of their studies, lithology, and characterization of ammonite zones in each region. Ammonites of the superfamilies Parahoplitoidea and Douvilleiceratoidea, which form the basis for the Middle Aptian stratigraphic framework, are discussed and their origin and taxonomic composition are briefly considered. Forty species of 12 genera and 5 families are described. The historical stratotype section of the Gargasian stage of the French Lower Cretaceous scale is discussed, including the history of its recognition and subsequent study, and its present state. The authors’ concept of the tripartite subdivision of the Aptian Stage in the Russian Scale is substantiated. The Middle Aptian deposits are described in detail, and the range and zonal subdivision of the Middle Aptian France, Great Britain, Germany, and other regions of the world are discussed. The correlation of the Middle Aptian in the Boreal and Tethyan realms is given.