Petromagnetic and paleomagnetic studies of sediments at the Kattasai-1 and -2 Paleolithic sites

This article presents the results ofpetromagnetic and paleomagnetic research of geological sediments at the Kattasai-1 and -2 Paleolithic sites located in the Western Tien Shan piedmonts (Uzbekistan). The geological study of these sites has revealed the signs of deluvial genesis of culture-bearing deposits whose absolute age, determined using AMS, U/Th, and TL dating methods, was in the second half of MIS 3. For establishing the relative paleomagnetic history of sediment formation and genesis, 28 samples were taken from the cross-section of the Kattasai-1 site and 26 samples were taken from the crosssection of the Kattasai-2 site. Analysis of magnetic susceptibility of the Kattasai-1 samples has shown that culture-bearing sediments resulted from intense sheet erosion, and the sedimentary material was transported by the flow in a suspended state. The analysis of the Kattasai-2 samples has revealed that the sediments were subjected to plastic deformation; the sediments from the Kattasai-2 section were unsuitable for studying excursions of the geomagnetic field. The sediments of the Kattasai-1 and -2 sites were formed on relatively steep slopes, which preconditioned specific features of sedimentation and acquisition of residual magnetization. The formation of sediments was influenced by intense sheet erosion along the slope, and plastic deformation of sediments under the impact of compression along the surface under gravity. These processes resulted in distinctive magnetic texture of the deposits and changing direction of the characteristic component of magnetization. Thus, it has been established that anomalous directions of polarity in the samples under study were not associated with geomagnetic excursions, but with conditions of sedimentation, such as sheet erosion and plastic deformation under the impact of gravity. For proving the existence of geomagnetic excursions in slope sediments, additional preliminary studies of the anisotropy of magnetic susceptibility are required.