Around the terminal Pleistocene — the period relevant to Arlington Springs — the calibration curve contains a region of significant divergence between radiocarbon years and calendar years.

Carbon-14 production was different during and immediately after the last glacial maximum, and the result is that radiocarbon ages from this period translate to calendar ages that are substantially older than the radiocarbon age in years.

A radiocarbon age of 10,960 ± 80 years BP, calibrated using the standard calibration curves, translates to a calendar age of approximately 12,710 to 13,010 calibrated years before present — roughly 13,000 calendar years ago.

The National Park Service’s Channel Islands Park timeline records the Arlington Springs occupation at 12,900 BP.