High-δ13C Paleoproterozoic carbonates from the Transvaal Supergroup, South Africa

Marbles from the Transvaal Supergroup (Kaapvaal craton, South Africa) record two positive carbon isotope excursions to average δ¹³C_carbonate values of ∼+6‰ to +8‰ (relative to V-PDB), separated by carbonates with normal-marine δ¹³C values (∼0‰ ± 2‰). These elevated values have been preserved through metamorphic devolatilization. Together with an already documented high-¹³C excursion in overlying rocks, three separate positive carbon isotope excursions occurred on the Kaapvaal craton in the interval 2.43 to 1.93 Ga. It is not yet clear how many of these excursions reflect global rather than local processes.