Palynological and sedimentological evidence from the Trans-Ural steppe (Russia) and its palaeoecological implications for the sudden emergence of Bronze Age sedentarism

At the turn of the second to the third millennium bc, fortified and systematically organized settlements along with a developed metallurgy emerged in the Trans-Ural steppe. In order to reconstruct the related vegetation and climatic changes in the area and to detect effects of human impact during the respective Bronze-Age Sintashta-Petrovka and Srubnaya-Alakul cultures (2100-1650 cal bc), palynological and sedimentological investigations accompanying archaeological excavations were carried out. Statistical analyses of pollen spectra from two sediment cores in the immediate vicinity of the settlement Kamennyi Ambar demonstrate substantial similarities in Bronze Age and present vegetation covers. Higher percentages of arboreal pollen, especially in respect of deciduous trees, and consistently high values of Artemisia within the regional spectra suggest that Bronze Age cultures developed in a relatively humid environment. Simultaneously, higher values of Chenopodiaceae, Plantago and Cichorioideae point to steppe degradation at local scales, whereas regional vegetation appears to have been relatively unaffected by human activities. Although more than 30 localities in the micro-region of Karagaily Ayat were analyzed, none of these sediment cores accounts for a continuous sedimentation during the last 9,000 years. Our results reveal that climatic fluctuations are not always directly reflected by sediment formation, with many non-climatic factors, such as post-sedimentary processes, local morphology and erosion believed to be crucial. Only the use of high resolution AMS radiocarbon dating is suitable to detect hiatuses, hence providing a valuable clue to the interpretation of palaeoenvironmental conditions.