Petrochemical analyses of the raw material outcrops in the Paleolithic of Northern Mongolia

Purpose. The article considers the petrographic and chemical analyses of artifacts from archaeological contexts and rock samples from the primary raw material outcrops and alluvial gravel. Artifacts were selected for analysis from the Kharganyn-Gol-5 and Tolbor-4, -15, -16, -21 collections for comparison. The varieties of raw material were identified by structural, textural, and mineralogical features observed in petrographic thin sections under polarized light at relatively low magnifications. Characterization of samples was conducted using instrumental neutron activation analysis (NAA) (margin of error = 5-10 %). Abundances of major elements in basalts (wt. %) were determined by X-ray fluorescence (XRF) spectrometry. To more precisely identify the sources of raw material, we have studied a number of geochemical modules in samples from exposed outcrops and from lithic artifacts, since such modules are less dependent on irregularities of the rock and to a greater degree characterize the physical and chemical conditions of sedimentation. Results. Using principal and trace element data obtained by XRF and NAA, it was found that the distributions of rock compositions from the outcrops of raw materials and the artifacts overlapped, suggesting that the sources of raw materials were nearby outcrops of the Early Permian Tulbur and Khargan formations or alluvial material originating from the same outcrops. Analyses have shown that the rocks vary widely in their chemical composition as a result of mineralogical and granulometric variability as well as structural and textural inhomogeneity, making it difficult to link the source of raw materials with specific rock outcrops. Lithic varieties with distinct matrices and structural features were identified within the groups of raw materials selected from their primary sources as well as within the archaeological collections. They represent 14 rock types used in the fabrication of stone tools with varying frequency. The rock samples selected for analysis exhibit fluctuating features of structure and color divisible into three primary categories: cherts (silica-rich sedimentary rocks) with a cryptocrystalline structure of chalcedony-quartz composition (nine varieties), tuffaceous siltstone (one variety), and coarse tuff and tuffites with siliceous cement (three varieties). Conclusions. Pleistocene sites in the Ikh Tulberiin Gol and Kharganyn Gol Valleys, usually located in close proximity to outcrops of suitable lithic raw material, exhibit some variation in reduction technology, and, accordingly, in the morphology of the artifacts produced, depending on the composition of the dominant types of stone utilized and the initial sizes of naturally-occurring fragments. Based on the analysis of geochemical indicators, it is probable that some raw materials were transported to Kharganyn Gol 5 from the neighboring valley, which may also have affected the size and morphology of the artifacts