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 C_org, N_org, 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 C_org values obtained are very low (below 0.05%), but reach a maximum of 0.1% in the middle of the fungal event zone. N_org 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 N_org and C_org. 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. δ¹⁵N_org values vary between 2.46‰ and 4.25‰, showing no significant changes in the fungal event zone. The δ¹³C_org values are all below −25‰, and reach a low of −27.41‰ in the fungal event zone. This negative shift in δ¹³C_org is an example of the global negative shift in δ¹³C found associated with the end-Permian extinctions and fungal event.