Inbuilt age, residence time, and inherited age from radiocarbon dates of modern fires and late Holocene deposits, Western Transverse Ranges, California

Radiocarbon dates of sedimentary deposits include the elapsed time between formation of the organic material and deposition at the sample site, known as the inherited age. Long inherited ages reduce the accuracy of estimates of the timing of depositional events used to infer paleoclimate change, fire histories, and paleoearthquake timing. An inherited age distribution combines the inbuilt age distribution, which reflects the age composition of the vegetation of the source area, and the residence time distribution, which includes transport and interim storage prior to final deposition. Differentiating residence time and inbuilt age is difficult given typical dispersion of ages in a sedimentary deposit. We address this problem by comparing charcoal dates from two modern fires in southern California, the 2020 Bobcat and the 2013 Grand Fire, with a well-dated late Holocene deposit in the Pallett Creek watershed. The modern fire deposits have negligible transport time (