Evidence of a prolonged drought ca. 4200 yr BP correlated to on-site prehistoric settlement abandonment from the Gueldaman GLD1 Cave in semi-arid N-Algeria.

Abstract:

Drought in Algeria is a recurring phenomenon and prolonged dry condition exerts a significant impact on local society. For instance, the most recent (1999-2002) drought, as part of a widespread drying in N-Hemisphere, brought this country considerable loss in regards to water resource and agricultural yields. A comprehensive understanding of past climate anomaly is relevant to predicting and mitigating future climate change effects. A few high-resolution well-dated paleoclimate records were recently established using speleothems in the Central and E-Mediterranean basin, but the scarcity of such records in W-Mediterranean prevents us from correlating past climate evolutions across the basin. Besides, climate deteriorations have long been argued to be linked with past cultural disruptions. However, in many cases such linkage is equivocal, in part due that existing climatic evidence has been derived from areas outside the distribution of ancient settlements, leading to uncertainty from complex spatial heterogeneity in both climate and demography. Here we present the first decadal-resolution Mid-Holocene climate proxy records from the W-Mediterranean basin based on the stable carbon and oxygen isotopes analyses of two U/Th dated stalagmites from the Gueldaman GLD1 Cave, N-Algeria. Comparing our records with those from Italy and Israel reveals synchronous (multi) centennial dry phases centered at ca. 5600 yr BP, ca. 5200 yr BP and ca. 4200 yr BP across the Mediterranean. New radiocarbon dating from this study well constrains the age of anthropogenic deposits (e.g., faunal remains, pottery, charcoal) excavated inside the cave. In-situ comparisons of evidence of climate and cultural change show that the timing of a prolonged drought at ca. 4400-3800 yr BP blankets the onset of cave abandonment shortly after ca. 4400 cal yr BP, supporting the hypothesis that a climate anomaly may have played a role in this cultural disruption.