Changes in carbon isotope ratios in the late Permian recorded in therapsid tooth apatite

Abstract

THE end of the Permian witnessed global extinctions of marine and terrestrial fauna1. As marine biogenic carbonate and atmospheric carbon dioxide are in long-term isotopic equilibrium, changes in carbon isotope ratios in marine carbonate strata should record changes that occurred at that time in atmospheric ratios; one might then expect a correlation between 13C/12C ratios in such marine sequences and those in terrestrial records that derive from carbon-bearing materials that incorporate atmospheric CO2. An example of the latter is fossil tooth apatite from herbivorous fauna. Correlations of this sort between marine and terrestrial records are, however, difficult to establish as they rely on particular characteristics of the isotope curves. Here we show that stable-carbon isotope ratios in tooth apatite from Diictodon (a mammal-like reptile), in the late Permian Lower Beaufort succession of the South African Karoo (∼260–245 Myr), show a progressive depletion in 13C that is very similar to trends in marine carbonates from late Permian deposits in Eurasia2–7. These results suggest that global changes in total biomass occurred towards the end of the Permian: primary production decreased and continental aridity increased8, leading to a depletion of 13C in atmospheric and oceanic CO2.