V. A. Zhamoida, A. Yu. Sergeev, L. M. Budanov, D. V. Ryabchuk, A. G. Grigoriev, I. A. Neevin, M. A. Mustafin

Evolution of morphogenesis and sedimentation processes in the coastal shelf of Beringia during Late Quaternary climatic changes

Abstract. The paper focuses on the problems of palaeogeography of the Bering Sea coastal shelf in the Neopleistocene–Holocene based on new geological and geophysical data obtained in 2021 by Karpinsky Institute during offshore operations, including 1,150 km of seismic profiling, side-scan sonar profiling, multibeam echo sounding, and underwater video observation. They identified local acoustic reflectors in the seismic records and associated them with marine isotope stages, which characterized and traced the distribution of five seismic units during the Pliocene–Quaternary time. A vibrating core and box corer sampled the deposits of all seismic units, except the oldest one. The analysis of seismic profiles traced the palaeogeographic development of the Bering coastal shelf dating from the Middle Neopleistocene. There were detected traces of six regressive phases in the Middle and Late Neopleistocene deposits, which apparently caused the Bering Isthmus Formation. The formation time of end-moraine ridges, including buried ones, was determined. In the Gulf of Anadyr, this is the end of the Middle Neopleistocene, in the Bering Strait — the second stage of the Upper Neopleistocene. There was established the amplitude of crustal subsidence (–60 m) in the eastern part of the Gulf of Anadyr in the Middle Neopleistocene.

Keywords: palaeogeography, Neopleistocene, Holocene, Bering Strait, seismic acoustics, seismic stratigraphy, glacial deposits