The Matuyama–Brunhes reversal in the loess-paleosol sequence of the Otkaznoe section (Terek–Kuma Lowland, Eastern Ciscaucasia)

Abstract

Detailed chronostratigraphy of loess-paleosol sequences (LPSs), based on a multi proxy approach and global correlation with sedimentary records, is essential for Quaternary environmental reconstructions. On the East European Plain, the Eastern Ciscaucasian LPSs are among the longest and the most continuously deposited in Europe. These sequences are comparable to the loess of China and Tajikistan in terms of their stratigraphic completeness and thickness (over 100 m), which allows development of high-resolution records. There, we introduce, for the first time, a comprehensive set of high-resolution data, including paleomagnetic, rock magnetic, grain size, and loss on ignition records, alongside X-ray diffraction and scanning electron microscopy analyses, for the Matuyama-Brunhes (M/B) transition in the Otkaznoe section (Terek-Kuma Lowland), Eastern Ciscaucasia. The M/B transition in the Otkaznoe LPS encompasses a ∼1.7 m thick zone, and includes the M/B precursor and the Matuyama-Brunhes boundary (MBB). The precursor to the M/B reversal is recorded in the loess, which correlates with marine isotope stage (MIS) 20, and is characterized by virtual geomagnetic pole (VGP) latitudes of approximately 0°. The MBB in the Otkaznoe section is located in the lower part of the MIS 19 paleosol, rather than in the MIS 20 loess, as was previously assumed. We propose that the M/B precursor in the Otkaznoe section can serve as a reliable chronostratigraphic marker for regional and global correlations, comparable to the M/B boundary. The impact of lock-in processes on the paleomagnetic record of the Otkaznoe section is insignificant.