Late Holocene landscape reconstruction in the Land of Seven Rivers, Kazakhstan

A landscape reconstruction for the late Holocene was carried out in the Land of the Seven Rivers, Kazakhstan, to investigate the environmental conditions during the prehistoric nomadic occupation of the Sakes (∼1st mill. BC). Two sampling locations were sedimentologically analysed: a) radiocarbon-dated late Holocene colluvial deposits and b) fluvial deposits of assumed late Pleistocene to early Holocene age. The geochemical and mineralogical components (ICP element analysis, carbon contents, grain size distributions, X-ray diffractometry) were investigated to identify synsedimentary weathering conditions. A modified weathering index (mCIA) was used to evaluate the weathering processes. The mCIA results were compared with the silt-clay-ratio as an additional indicator for post-depositional soil forming processes. Differences within the silt-clay-ratios and mCIA indexes revealed that during the late Holocene, increased erosion processes occurred in the catchment. A first, tentative geochronology is based on radiocarbon and luminescence ages, ranging from 14.5 ± 1.4 ka to 3.23 ± 0.07 cal ka BP for the colluvial deposits. This paleoenvironmental reconstruction is supplemented by a detailed geomorphological characterization of the present landscape (relief, landforms and landscape units) close to the Sakian graves.