Paleontological studies of the Devonian-Carboniferous boundary beds of Berchogur (Western Kazakhstan): possibilities of global correlation

Research subject. Devonian-Carboniferous boundary beds in the Berchogur Depression (Western Kazakhstan). New data on the fauna of ammonoids, conodonts, and foraminifers from the Berchogur sections were obtained during fieldwork studies in 2018–2019. Aim. Identification of episodes of the Global Hangenberg event (crisis) in the Berchogur section and correlation of the potential markers of the base of the Carboniferous in this section. Materials and Methods. The research was conducted using paleontological and lithological methods. Results. The study of fossil assemblages and rock lithology exposed by new excavations suggests that the markers of the Hangenberg event are present in the section; moreover, they can be correlated with the phases of this event in the sections of Western Europe. A correlation of ammonoid, conodont, and foraminiferal zones is proposed. It is shown that the conodont S. (Eo.) praesulcata in the Berchogur section first appears in Member 2b, and the first appearance of S. (Eo.) sulcata is recorded in Member 3b. Based on the findings of ammonoids of the genus Acutimitoceras, Members 3b and 3c can be correlated with the upper part of the prorsum ammonoid Zone, which corresponds to the level of appearance of S. (Eo.) sulcata. The intervals corresponding to episodes of the global Hangenberg event (pre-crisis, crisis, and partly post-crisis) are provisionally identified in the section. Conclusions. The pre-crisis interval corresponds to the abundance of foraminifers in the Q. kobeitusana substricta Zone and the Upper expansa and lower part of the Lower praesulcata conodont zones. The so-called crisis prelude corresponds to the extinction of the quasiendothyrid foraminiferal community and the upper part of the Lower praesulcata Zone (Member 2a2). The Hangenberg Extinction, or the lower crisis interval, corresponds to the clays of Member 2b in, and to the interval of most of the Middle praesulcata Zone – the lower part of the Upper praesulcata Zone, and to the Hangenberg black shales in Europe. The subsequent regressive episode (Member 3a) corresponds to the upper part of the Upper praesulcata Zone. The members with ammonoids (3c) and conodonts of the sulcata Zone (3b and 3c) and Member 4 correspond to the transgressive phase and are considered equivalent to the Stoсkum Limestone of the Rhenish Massif.