A closer look at clasts and groundmass: Micromorphological features in sediments with archaeological significance in Obishir and Katta Sai complexes (Central Asia)

The aim of this study is to investigate the relationship between coarse and fine material in sediments at four archaeological sites in Central Asia, which share a common characteristic of coarse clasts dispersed within a silty matrix. By using micromorphology and grain size analysis, the study aims to understand the microscale processes that have affected the geogenic material and, by extension, the potential impact on the archaeological assemblages. The four sites studied are Obishir-1, Obishir-5, Katta Sai 1, and Katta Sai 2, which are located at the toe or along a slope in Kyrgyzstan and Uzbekistan. The study focuses on the micro-features occurring on the surfaces of pebble-sized clasts and identifies four typical features: loamy cappings, loamy coatings, secondary calcium carbonate accumulations, and cracks. The processes related to these features are identified as alteration of the mineral grains, frost action, redeposition, and pedogenetic and anthropogenic processes. The study concludes that the primary contact between the two components has been disrupted in most cases, and suggests that the findings can be used to analyze site formation and post-depositional processes at archaeological sites. Furthermore, analogies with gravel-sized artifacts can be drawn, particularly with regard to secondary calcium carbonate accumulation.