ESR/U-series chronology of early Neanderthal occupations at Cova Negra (Valencia, Spain)

Abstract

The spatiotemporal repartition of Neanderthal populations throughout the late Middle and early Upper Pleistocene is of great interest for our understanding of human evolution. Establishing a reliable chronology for human-bearing layers from prehistoric sites is thus essential for the study of Neanderthal population dynamics prior to modern human arrival in Europe. Cova Negra (Valencia, Spain) is one of the richest sites documenting Neanderthal fossil bones in the Iberian Peninsula (Arsuaga et al., 1989, 2007; Villaverde et al., 2014). The stratigraphic sequence includes 15 Middle Palaeolithic layers. Among them, four were dated by the ESR/U-series dating method on enamel from six herbivore fossil teeth. Equivalent doses were obtained using the additive dose method on multi-aliquots. U-content, 234U/238U and 230Th/234U isotopic ratios were measured using ICP-QMS. Results indicate that dental tissues from two out of six analysed teeth underwent U leaching during burial. Thus, it does not allow the calculation of US-ESR (U-series-ESR, Grün et al., 1988) ages for these samples. However, ages calculated using AU model (Accelerating Uptake, Shao et al., 2012) are discussed together with biochronological data and previous absolute ages obtained for the archaeological sequence. Age results indicate that Neanderthals occupied Cova Negra during MIS 8 to 6, between 273 ± 26 ka and 146 ± 34 ka. These results suggest that human occupation took place at the end of the Middle Pleistocene, and hence it is older than proposed by previous TL ages obtained on sediments (Arsuaga et al., 2007). By contrast, our ESR/U-Th ages suggest that Neanderthals were present in the cave 100 ka earlier than initially proposed, in agreement with TL ages obtained on burnt flint (Villaverde et al., 2014). This implies that the Cova Negra human specimens could represent one the earliest occurrences of Neanderthal presence in the Iberian Peninsula.