Late Pleistocene-Recent Atmospheric delta-13C Record in C4 Grasses

Abstract

Samples of Setaria species from packrat middens, herbarium specimens and modern plants preserve a record of delta-13C of atmospheric CO2 from 12,600 BP to the present. No secular trend is detected between 12,600 and 1800 BP, when the mean value of delta-13C during that period was -6.5 +/- 0.1 per mil (the error is the standard deviation of the mean). Our value agrees with delta-13C averages of pre-industrial CO2 from polar ice cores, and differs significantly from modern regional (-8.2 +/- 0.1 per mil) and global (-7.7 per mil) values, which are higher because of fossil fuel burning.