Biomagnetostratigraphy of the Eastern Gobustan’s paleogene rocks

Abstract

On the territory of Azerbaijan, Paleogene deposits are widespread and often have facies alteration. To address the issues of stratigraphic, paleogeography, facies and paleoecological directions, a detailed stratigraphic basis of both the region as a whole and its individual sections is required. This article presents the results of joint magnetobiostratigraphic studies of the Paleogene deposits of the Greater Caucasus (Azerbaijan) in order to clarify the boundaries of the Paleocene, Eocene, Oligocene and Miocene. Biostratigraphically dated Paleogene deposits of the Khilmili, Pirakushkul, Dzhangi sections (southern slope of the Greater Caucasus) were chosen as the object of study. Paleomagnetic studies of the Paleogene deposits of Azerbaijan showed frequent reversals of the geomagnetic field of this period. The results of scientific studies of the southern slope of the Greater Caucasus confirmed this fact. We have identified two paleomagnetic zones: 1) Khorem (Maastrichtian 70 Ma - Eocene 45 Ma) (zones of reverse polarity prevail in it, but the upper part of the Paleocene has a direct polarity) and 2) Sogdiana (RN-Oligocene and Miocene - characterized by alternating direct and reverse polarity paleomagnetic field). In the Lower Paleocene, 2 subzones of direct polarity were distinguished: Danian and Selandian. The position of the R-zone made it possible to draw the boundary between the Danian and Selandian stages. The identification of a paleomagnetic zone of reverse polarity contributed to the determination of the boundary between the Selandian and Thanetian stages. This result was confirmed by identifying changes in the micro-faunistic composition of deposits and observing the nature of variations in micro-floristic complexes. Such a paleomagnetic zone of reverse polarity is the benchmark (plug) for establishing the boundary between the Mons and Thanetian stages. Keywords: paleomagnetism; southern slope of the Greater Caucasus; Paleogene; magnetostratigraphic boundaries.