Stratigraphic architecture and alluvial geoarchaeology of an ephemeral fluvial infilling: Climatic versus anthropogenic factors controlling the Holocene fluvial evolution in southeastern Spain drylands

Two stages of depositional high-discharge fluvial environments are recorded in the infilling of a rock shelter in a canyon of the Segura River, namely: (1) First stage: aggradational alluvial gravels in the lower part, interpreted as braided channel bars (Seventh millennium to 2030 cal BC), and (2) Second stage: slackwater flood deposits in the upper part (between 2030 cal BC and after 900 AD) during a stage of main channel incision. Reconstructed flood discharges for the second stage were a minimum of 700 m3/s. Extreme palaeofloods that inundated the cave from the canyon inlet were successively higher and are correlated to quick-rising flash floods. The characteristics of cultural remains preserved by flood deposits reveal long periods of human cave occupation (and passage through the canyon) without extreme floods occurring. These long periods of low-discharge fluvial flow punctuated by catastrophic flash floods are linked to a torrential fluvial regime. The torrential regime is the current hydrologic and climatic scenario in the streams of semi-arid southeastern Spain. It is discusses the climatic versus anthropogenic factors affecting the fluvial development. We conclude that the archaeo-fluvial record of the Pozo Rock Shelter indicates that the present-day semi-arid conditions of the southeastern Spain drylands extend back to circa 4000 yr BP. Methodologically, the combination of fluvial palaeohydrology and geoarchaeology appears to be a robust tool to reconstruct long-term Holocene climate changes.

► Combination of geoarchaeology, bedforms in slackwater and hydrology of palaeofloods
► Dating Holocene fluvial processes
► Fluvial bedforms evolution reflect a climatically-controlled river regime change.
► We extend the nowadays semi-arid climate of southern Spain until 4000 yr BP.