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 (similar to 1st mill. BC). Two sampling locations were sedimentologically analysed: a) radiocarbondated 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. (C) 2011 Elsevier Ltd and INQUA. All rights reserved.