Stratigraphy of the Maikop Group and Pteropoda Beds in northern Azerbaijan

Deepwater sections of the Maikop Group (Oligocene-lower Miocene) and overlying lower-middle Miocene sediments are studied near the Perekishkyul Settlement in lower reaches of the Sumgait River, northern Azerbaijan. Several lithological reference levels and the Spiratella (Pteropoda) Beds are used to correlate preliminarily these uniform clayey sections barren of benthic fossils. Based on distribution of the organicwalled and calcareous phytoplankton, spores, pollen and ichthyofossils, the sections are first subdivided in detail and dated. Distinguished in the sections are two regional levels characterizing distortions in the basin hydrological regime during the late Oligocene (level with large Leiosphaeridia and Pterospermella) and Burdigalian (level with dominant dinocysts of the genus Batiacasphaera), and separate intervals with diverse phytoplankton and ichthyofossils. The Tarkhanian sediments are marked by first-appearing oceanic nannoplankton with Sphenolithus heteromorphus and deepwater ichthyofauna with Vinciquerria merklini. The Karaganian is established at the first occurrence level of peculiar endemics (Sardinella karaganica W. Dan. and Mugil karaganicus Swich.) among ichthyofauna.