The terminal Pleistocene is also a period when the curve has a distinctive shape — a relatively steep slope in some regions, meaning that a small change in radiocarbon age corresponds to a relatively small change in calendar age.

This reduces the calendar-year uncertainty in some respects: even with radiocarbon measurement uncertainty of ±80 years, the corresponding calendar-year range is constrained by the curve’s shape.

The more recent IntCal calibration curves — versions released through 2020 — incorporate additional data from marine sediments, cave speleothems, and extended floating tree-ring chronologies, and are more precise in the terminal Pleistocene than earlier versions.

The Arlington Springs date, recalibrated with the most recent curves, produces a calendar range centered on approximately 12,900 calendar years ago — consistent with the range that had been published and consistent with the NPS timeline designation of 12,900 BP for the site.