A stable isotope study of mammal skeletal remains of mid-Pleistocene age, Arago cave, eastern Pyrenees, France. Evidence of taphonomic and diagenetic effects
Abstract This study reports a set of 85 oxygen isotope measurements carried out on fossil bones of Cervus elaphus, Ovis sp. and Equus sp. from archaeological excavations in the Arago cave, eastern Pyrenees, south-eastern France, of ages ranging from about 650 to 450 ka. A large section of the thick sediment sequence filling the cave was flushed, for an unknown time, by meteoric water through a large opening in the limestone ceiling caused by karst erosion. Under these conditions, part of the biogenic material underwent partial solution and diagenesis; these processes may have caused considerable effects on the original isotopic composition of bone phosphate. The range of the isotopic values obtained from each stratigraphic level is quite wide, particularly in the case of horse remains whose δ18O(PO3−4) values cover a range of about 5‰ in the same stratigraphic level. However, a few isotopically heavy values were obtained from the three species which suggest the possibility of very warm climatic episods or, alternatively, of climatically dry periods. Altogether, the results clearly show that it is not possible to obtain quantitative palaeoclimatological and palaeoenvironmental information from fossils which underwent taphonomic and diagenetic effects, that these effects may take place readily and that time is one of the less important parameters affecting bone preservation. The uncertainties existing in the case of relatively old fossil bones (not always shared by isotope geochemists) are thus directly confirmed.