Archaeology and Its Relevance to Climate and Water Level Changes: A Review

Abstract

A brief review of archaeological data is given and their relevance to the reconstruction of climate and water level changes is discussed. Research since the nineteenth century has established a good database, especially for the southern Aral Sea region (ancient Khorezmia). Human occupation of the area first began during the Late Pleistocene, but was interrupted by the last glaciations. The Aral Basin was again settled by Neolithic populations after the 8.2 ky event and continued until now. A humid climate is indicated for the early period, as several large lakes in the Kyzylkum sustained Neolithic settlements, however, the water level of the Aral Sea may have been low, since the Amudarya drained to the Caspian Sea via the Uzboi at this time. Towards the end of the Third Millennium bc in the northern Aral region forest–steppe vegetation predominated, as indicated by a cultural and economic change in archaeological culture. Around 2000 bc the Amudarya stopped flowing to the Caspian Sea, changing its course to the Akchadarya channel which was now densely settled for the first time. The water level may have reached 40–45 m above sea level (a.s.l.). Climate change is indicated as causing the Scytho-Saka migration at the beginning of the First Millennium bc. Beginning from the sixth century bc irrigation activity may have influenced the water balance and possibly the Uzboi was active for part of this period. A major regression in the fourth century ad was probably caused by climate, but aggravated by extensive irrigation systems. In the tenth century water level was below 53 m a.s.l., although both Amudarya and Syrdarya drained to the Aral Sea. Extreme regressions in the early thirteenth century and at the end of the fourteenth century were caused by war, possibly also influenced by earthquakes. In both cases dams were destroyed and the Amudarya drained to the Sarykamysh depression and/or the Uzboi, withdrawing water supply from the Aral Sea. A transgression sometime after the fourteenth century is documented by marine sediments overlying archaeological sites and may have existed as late as the nineteenth century.