Quantifying marine reservoir effects (MREs) across time and space is crucial for establishing accurate archaeological chronologies, including the activities of past hominines. Although the northern Iberian Peninsula shows a high density of Upper Paleolithic sites and marine shells are frequently found in these assemblages, quantification of MREs in this coastal region remains limited. We performed Bayesian modeling of radiocarbon measurements from both terrestrial (Capra pyrenaica, Cervus elaphus and other herbivores unidentified at species level) and marine (Littorina littorea Linnaeus, 1758 and Patella vulgata Linnaeus, 1758 taxa) archaeological samples recovered from the Tito Bustillo cave (Asturias, Spain) in order to determine the ΔR values for northern Iberia during the Lower Magdalenian period (ca. 20–17 ka cal BP). For the time span between 18.6 and 18.2 ka cal BP we estimated ΔR values of –298±44 14C yr and –495±122 14C yr for the periwinkle L. littorea and the common limpet P. vulgata, respectively. This finding has significant implications for future archaeological research in the northern Iberian Peninsula, as researchers must apply distinct ΔR values depending on the mollusk species selected for radiocarbon dating. Furthermore, the consistency between our calculated ΔR value for P. vulgata and previously recorded data for the same taxon from a neighboring coastal region (Cantabria, Spain) suggests remarkable stability in the marine environment of this area during the Lower Magdalenian period.

The authors describe the discovery of the first human burial of Magdalenian age to be found in the Iberian Peninsula—the partial skeleton of a young adult whose bones were stained with red ochre. The burial was well stratified in a sequence at the vestibule rear running from the Mousterian to the Mesolithic, and was adjacent to a large block that had fallen from the cave roof and been subsequently engraved. A preliminary AMS radiocarbon date on associated faunal remains from the ochre-stained, galena speckled burial layer yielded a date of 15700 BP, while a hearth directly above the burial is dated to 15 100 BP, placing the interment of this individual in the Lower Cantabrian Magdalenian, the period of most intensive human occupation of El Mirón Cave during the Upper Palaeolithic.