Temperature and precipitation regime in LGM human refugia of southwestern Europe inferred from δ13C and δ18O of large mammal remains
Résumé
The climate shift of the Last Glacial Maximum (LGM) strongly impacted the vegetation cover and related trophic chains of western Europe. Harsh, cold and dry conditions then prevailed in most regions, strongly impacting migrations and survival of human beings. Nonetheless, environments suitable for mammalian fauna to survive persisted in SW Europe thus providing refugia for hunters. Tooth enamel from large herbivorous mammal remains from archaeological sites located in southwest France and Spain were analyzed for their stable carbon and oxygen isotope compositions for documenting paleotemperatures and paleoprecipitations. These sites were occupied by humans between 25 ky and 16 ky. Skeletal remains of Cervidae, Equidae and Caprinae suggest colder and drier conditions relative to present-day. Paleoprecipitations were reconstructed from a modern-based transfer function using δ13C-values of apatite carbonate, then corrected for the low atmospheric pCO2 value of the LGM. They ranged from ≈250 mm yr-1 on the Mediterranean façade, to ≈550 mm yr-1 on the Atlantic side. Setting the δ18O-value of the northeastern North Atlantic LGM-surface water to +0.8‰, based on Biscay Golf marine core studies, mean air temperatures inferred from 18O-data in apatite calcite were close to 14-15 °C (Mediterranean) and 6 °C-10 °C (Atlantic), i.e., about 4-5 °C and 5-8 °C higher than pre-industrial temperatures, respectively. The two areas thus define distinct clusters of air temperatures and precipitation regimes with strong negative offsets vs the Present. These isotopically-reconstructed climate conditions indicate a strong control from proximal surface ocean/marine waters, in particular of mean annual air temperatures.
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