The wild river and the last Neanderthals: a palaeoflood in the geoarchaeological record of the Jarama Canyon (Central Range, Guadalajara province, Spain)

Abstract

The Upper Jarama Valley is located on the southern slope of the eastern part of the Spanish Central Range. In this area the valley cuts and runs through a narrow strip of carbonated rocks creating a karstic canyon with many caves and rock shelters in the cliffs at both banks. One of this rock shelters, Jarama VI, is located on the left bank of the Jarama River, in the middle of a hillside, 23 m above the river, and is partially filled up. The lithostratigraphic sequence begins with the, stratum alteration (unit 4), and a cold autochthonous clastic deposit follows it with a human occupation of the Middle Paleolithic (unit 3). The upper part of the unit 3 was affected by a strong erosion due to a huge palaeoflood, which caused the sedimentation of a sandy series (sub-unit 2.3) that ends in flood silts (sub-unit 2.2). Charcoals have yielded the 14C date 32.600 ± 1.860 BP (Beta-56639). These deposits have their origin in a fluvial palaeosuperflood. At the top part of this level and inside the rock shelter there are clastic intercalations (sub-unitl 2.1) with plenty of Mousterian artefacts radiocarbon dated to 29500 ± 2700 BP (Beta-56638). A stratigraphic hiatus separates units 2 and 1. Unit 1 is a cold autochthonous clastic deposit containing many human occupation remains of the Early Upper Paleolithic age. The sequence is sealed by a stalagmitic crust (unit 0). The 14C dates from Jarama VI seriate the palaeoflood in the chronostratigraphic scale. Therefore, both dates 32600 ± 1860 BP (Beta-56639) and 29500 ± 2700 BP (Beta-56638) date the upper part of level 2 somewhere in the Late Upper Pleistocene, between the isotopic stages 3 and 2.