Preliminary results of study of pigments from the rock art sites of middle and lower stream of the Shilka river in the Trans-Baikal region

This year, field and laboratory work continued on the study of the rock art sites in the middle and lower streams of the Shilka River in the Trans-Baikal region. New drawings were discovered as a result of the comprehensive documentation of the rock art site near the Sredne-Shaykino River. Microanalytical studies of the pigments from all the four sites were performed using SEM-EDX and micro-Raman. The preparation of cross-sections allowed analyzing weathered samples layer by layer. Each sample contains a multilayered structure with at least three individual layers rich in silicon, aluminum, phosphorus, and calcium corresponding to the changes in the geochemical environment. Analysis of 9 samples from the Sredne-Shaykino site demonstrated that the sequence of layers in different samples does not match. These variations might be related both to local composition of the bedrock and the position and orientation of the panels with drawings. All paintings were made in red color. Hematite was detected using micro-Raman spectrometry. Sheaths, which are characteristic of biogenic hematite, were revealed in the pigment samples. The discovery of biohematite in the samples from all four sites makes it possible to evaluate the presence of a specific cultural tradition in the use of such raw materials, as well as the relative simultaneity of the creation of the studied sites. This study provides new insights into the artistic practice of the ancient population of the Trans-Baikal region and develops the framework for further search of the pigment’s sources and paint preparation techniques.