The Lithological and Geochemical Characteristics and Paleoclimatic Conditions of the Formation of Upper Cretaceous Sediments of the Russian Plate Epicontinental Basin in the Region of the Ul’yanovsk–Saratov Trough

• Published in: Moscow University geology bulletin 2021-05, Vol.76 (3), p.257-269
• Main Authors: Gabdullin, R. R., Puzik, A. Yu, Merenkova, S. I., Migranov, I. R., Badulina, N. V., Ivanov, A. V., Kazurov, M. D.
• Format: Article
• Language: English
• Subjects: Cooling; Cretaceous; Cycles; Denudation; Earth and Environmental Science; Earth Sciences; Geochemistry; Geology; Humidity; Lithology; Zonation
• ISSN: 0145-8752; 1934-8436
• DOI: 10.3103/S0145875221030054

The results of a geochemical, paleogeographic, and paleoclimatic study of a cyclically constructed section of upper Cretaceous deposits near Vol’sk city (Saratov oblast) are presented. Elementary layered cyclites and cyclic variations of several certain parameters were associated with the Milankovich astronomical-climatic cycles. Paleotemperature, humidity, and paleobathymetry curves were compiled. Paleotemperatures of the land surface in the denudation areas were obtained from the chemical index of alteration (CIA). Climatic cyclicity was established in the Turonian–Campanian interval, including a period of relative cooling (Turonian–Coniacian) with a paleotemperature of approximately 20°С, the period of relative warming in the mid–late Campanian (20–24°С), the cooling time at the end of the late Campanian (19–21°С) and the period of warming at the turn of the Campanian and Maastrichtian and in the early Maastrichtian time, there are two climatic cycles in Maastrichtian age, beginning with a time of relative cooling (approximately 19°С) and ending with a time of relative warming (approximately 20°С, at the end of Maastrichtian to 25°С). The cycles of climate humidity change are also determined: two cycles in Campanian time, three cycles in early Maastrichtian, and one cycle in late Maastrichtian. The boundary of the early and late Maastrichtian corresponds to the change of arid conditions to humid ones. The paleobatimetry curves show transgressive–regressive cycles: one in the late Turonian–Coniacian time, two in the late Campanian time, five in the early Maastrichtian time, and one in the late Maastrichtian time. Depth variations were estimated: in the Turonian–Coniacian time in the range of 70–80 m, in the Campanian–Maastrichtian time, the paleobatimetry consistently increased and changed from 100 to 200 m (on average approximately 150 m). These results provide an idea of the migration of the boundaries of the arid belt in the Late Creataceous and main features of the climatic zonation, which is important for regional and global paleoclimatic reconstructions, as well as for the history of the development the Russian Plate in the Ulyanovsk–Saratov region.