Significance of carbon, nitrogen and their isotopic changes in a Permian-Triassic non-marine boundary section at Carlton Heights (Karoo Basin), South Africa

We performed analyses of Corg, Norg, δ13C org, and δ15N org from the non-marine Permian-Triassic boundary section at Carlton Heights in the Karoo Basin, South Africa. The Carlton Heights section is thus far unique in the Karoo in containing the Permian-Triassic palynological boundary between the Upper Permian Klausipollenites schaubergeri Zone and the Lower Triassic Kraeuselisporites-Lunatisporites Zone, separated by a 1-m thick “fungal event” zone, marked by abundant fungal cell remains (Reduviasporonites) and woody debris. The Corg values obtained are very low (below 0.05%), but reach a maximum of 0.1% in the middle of the fungal event zone. Norg varies little from 0.02%, except in the middle and top of the fungal event, where it rises to 0.04%. C/N ratios are extremely low throughout the section (less than 3), reaching a maximum of 2.49 during the fungal event, coincident with the peaks in Norg and Corg. The very low C/N ratios resemble those found in modern burned soils with low bacteria/fungi ratios, and the lack of variation suggests no change in the organic matter source. δ15Norg values vary between 2.46‰ and 4.25‰, showing no significant changes in the fungal event zone. The δ13Corg values are all below −25‰, and reach a low of −27.41‰ in the fungal event zone. This negative shift in δ13Corg is an example of the global negative shift in δ13C found associated with the end-Permian extinctions and fungal event.