Landscape development and soils around the Bronze Age settlement Kamennyi Ambar, southern Trans-Urals, Russia

Abstract

Landscape and soils around the prehistoric Bronze Age site of Kamennyi Ambar, southern Trans-Urals, have been studied. The topography of the Trans-Ural peneplain was formed by denudation during Mesozoic and Tertiary. The resulting gently undulating plain was subsequently dissected during Pleistocene under periglacial climatic conditions, and wide valleys with gentle slopes were formed. The saprolized pre-quaternary rocks are covered by thin layers of quaternary sediments, which are sometimes loess-containing. Deposits of in-situ loess are almost absent. Most probably, deluviation under periglacial conditions played the dominant role and prevented the formation of loess deposits. Thin loess deposits are preserved only in some flat watershed positions. The Quaternary layers sometimes contain strongly weathered coarse bedrock components indicating a solifluidal genesis of the cover beds on the slopes. The degree of weathering of the autochthonous components increases towards the water divide where the cover beds consist almost completely of pre-Quaternary saprolite. The slopes of the Karagaily Ajat valley are structured by numerous smaller tributary valleys which usually have a yellow-brown loam fill and show in their lower parts gully-like linear erosion features. Decalcified Haplic Chernozems are prevalent soils in the fills of the tributary valleys, at the lower slopes of the Karagaily Ajat-valley, and in the loams of the Lower Terrace. When clay cutans and coatings were observed in the subsoil the soils were identified as Luvic Chernozems. On the gentle slopes, Mollic Leptosols or Leptic Regosols (Mollic) are developed in thin cover beds. Up the slope, the depth of the humus horizons decreases. When examining the layer succession of the near surface underground and the associated soils along transects across the tributary valleys, it was found that the thickness of the cover beds on the slopes increases towards the valley floor. In the soils of the Lower Terrace varying salt contents can be found. Mollic Solonetz were identified therein. Within the excavation area in Kamennyi Ambar, Anthrosols and Solonetz were found in the compacted layers of the older Sintashta culture, while Haplic Chernozems (colluvic) with similar features like the virgin soils have developed in the fillings of younger pit houses.