Is climate the main driver of Mid-Holocene settlement dynamics on the Varamin plain?

<p>For different areas throughout West Asia and the Middle East, settlement discontinuities and periods of cultural decline in the Mid-Holocene have been attested. Whether these phenomena were caused mainly by climatic factors, especially periods of drought, has been an ongoing scientific debate of the last decade(s).&#160; One of these regions, the Varamin plain, is located few kilometers east of Teheran on an alluvial fan along the southern slopes of the Elburs-mountain-range (Northern Iranian Highlands). A recent archaeological survey on the Varamin plain revealed a striking absence of archaeological finds for the end of the Proto-Elamite period (Early Bronze Age) between approximately 5000 and 4100 BP that has been interpreted as a (temporal) abandonment of the plain. This crisis presumably lasted until the beginning of the Iron Age around 3500 BP.</p><p>Since paleoenvironmental and paleoclimatic information for this region are scarce, this study makes use of 3 different approaches to unravel the Holocene climate variability in West Asia in general and the Northern Iranian plateau specifically: a) analysis of climate reconstructions, b) a high-resolution snapshot simulation performed in ICON-NWP for the mid-Holocene time-slice (7000 BP) and c) a transient simulation performed with the Max Planck Institute Earth System Model (MPI-ESM) spanning the period from 8000 BP to pre-industrial (PI, 100 BP).</p><p>The comparison of the regional proxy-based climate reconstructions reveals a considerable degree of hetegorenity, impeding any straightforward inferences regarding possible paleoclimatic forcings for settlement dynamics. In particular, no specific drought period can be identified that coincides with the settlement crisis.</p><p>The model results show that there is a general aridification trend between 7000 BP and PI in West Asia. While absolute annual mean precipitation changes are small, the model data reveal a shift in seasonality of precipitation with drier autumns and winters but substantially wetter conditions during spring during mid-Holocene times. In combination with longer and colder winters during the Mid-Holocene, this may have enhanced water availability and therefore favored agricultural production.&#160; Superimposed on this minor aridification trend, the model shows pronounced climatic variability with distinct multi-decadal wet and dry periods with variations of up to +/-12% in precipitation. Therefore, we cannot exclude that climatic events and variability including their geomorphological responses may have played a role in settlement discontinuties, but we can not clearly identify climate changes as the main driver.</p>