Carbon cycle dynamics following the end‐Triassic mass extinction: Constraints from paired <i>δ</i>¹³C_carb and <i>δ</i>¹³C_org records

Abstract

Constraining the carbon isotopic changes associated with the end‐Triassic mass extinction is key to understanding the causes of the extinction and dynamics of recovery from it. Yet the pattern and timing of δ 13 C variation surrounding the extinction remain poorly constrained. Here we present close to 1000 new δ 13 C measurements from six newly sampled sections in Italy. We observe a sharp negative excursion in δ 13 C carb coincident with the disappearance of the Triassic fauna, and two positive excursions above it. The negative δ 13 C carb excursion in these sections does not occur in δ 13 C org suggesting a possible diagenetic origin. In contrast, the interval of elevated δ 13 C occurs in both carbonate and organic carbon, suggesting that it is likely to be a primary feature. The positive excursions in the Lombardy Basin (southern Alps) and Mt. Cefalo (southern Apennines) appear to be time correlative on the basis of their position above the disappearance of characteristically Triassic biota. However, it is less certain that they are time correlative with positive excursions in other sections worldwide, as few options exist that honor both bio‐ and chemostratigraphy. Nonetheless, similarity to other events that are interpreted as global, as well as carbon cycle considerations, suggest that the isotopic enrichment is best interpreted to reflect a shift in the isotope composition of the global surface carbon reservoir. Our data indicate that perturbation of the global carbon cycle was not confined to the immediate vicinity of the extinction interval, but rather persisted for substantial length of geologic time afterwards.