Dating oxalate minerals 20-45 ka

We report a test of the dating of oxalate minerals near the radiocarbon limit. Oxalate salts are used for estimating the ages of prehistoric rock paintings and carvings, but uncertainties have existed about the origin of the carbon they contain. Sediments at the Carpenter's Gap 1 rockshelter, Western Australia, have been conventionally radiocarbon dated at about 34000 years old, providing independent evaluation for the ages of buried oxalate crusts associated with them. Accelerator mass spectrometry radiocarbon (AMS C-14) assays of carbon in rapidly oxidized oxalate ions from these crusts produce age estimates marginally older than the covering sediments. (c) 2004 Elsevier Ltd. All rights reserved.