Extended-range luminescence chronologies for the Middle Pleistocene units at the Sima del Elefante archaeological site (Sierra de Atapuerca, Burgos, Spain)

The Sima del Elefante site is located within the Sierra de Atapuerca karst system (Burgos, northern Spain), and forms part of a series of important Early, Middle and Late Pleistocene archaeological complexes that have been dated previously with luminescence techniques (Gran Dolina, Galería Complex, Sima de los Huesos, Galería de las Estatuas). This study focuses on the upper Middle Pleistocene units (TE18 and TE19) at Sima del Elefante, which contain Acheulean and transitional lithic assemblages (Mode 2/3), as well as large and small mammal fossils. Importantly, these uppermost units are associated with a sediment plug located in the cave's interior at Galería Baja, which marks the closure of a significant palaeoentrance to the Atapuerca karst system. Establishing the accumulation history of these related deposits is important for understanding both Lower Palaeolithic technological dynamics via comparisons with similar levels at other Atapuerca sites (i.e., Gran Dolina and Galería Complex), as well as past human occupation patterns and carnivore use of (and accessibility to) the caves. We present single-grain TT-OSL and multi-grain pIR-IR chronologies for the Sima del Elefante upper sequence and the Galería Baja sediment cone, as well as U-series dating results for a stalagmitic crust capping the combined clastic infill sequence. The paired luminescence ages for the upper occupation levels are in agreement with each other and reveal that the host deposits accumulated 576–481 ka for the TE18 stratified scree layers, 266–237 ka for TE19 and 206–250 ka for the Galería Baja upper cone section (weighted mean 2σ age ranges). A concordant U-series age of 202 ± 65 ka is obtained for the overlying stalagmitic crust at Galería Baja. The Sima del Elefante ages are consistent with those previously obtained using U-series and biochronology, confirming that there is an erosional unconformity and complex carbonate deposition phase associated with the upper layers of unit TE18 and that the original cave entrance likely closed by ∼200 ka. Chronological correlation with other Atapuerca sites reveals potential equivalence between TE18 and unit TD8 (at Gran Dolina), and between TE19 and units GIIb–GIIIb (at Galería Complex) and, possibly, TD10.1 and TD10.2 (at Gran Dolina), though more refined dating is required to confirm the latter.