Stable Isotope and Radiocarbon Analyses of a Black Deposit Associated with Pictographs at Little Lost River Cave,Idaho

A glossy, black deposit covers much of the ceiling and walls of Little Lost River Cave No. 1, Idaho. This site is of particular interest because of the red, orange, and yellow pictographs underlying the coating. Carbon and nitrogen stable isotope analysis has allowed us to better understand the nature and origin of the deposit. With a δ¹³C value of −20·1‰, δ¹⁵N value of +14‰, and a C/N ratio of 5·6 after removal of inorganic carbon from the sample matrix, the deposit appears to have been derived from animal tissue, not plant. Plasma chemical extraction of carbon from the organic material in another sample of the deposit, followed by accelerator mass spectrometric analysis, yielded a minimum uncalibrated radiocarbon age of 2990±50 bp for the paintings. This preliminary evidence suggests that the deposit may be a cooking residue.