THE EARLY TRIASSIC CARBON ISOTOPE RECORD OF NORTH AMERICA: EVIDENCE FOR GLOBAL PERTURBATIONS OF THE CARBON CYCLE

Large perturbations of the global carbon cycle at and after the end Permian mass extinction have been reported by previous studies, on the basis of the carbon isotope record of marine and terrestrial sediments. The existing carbon isotope dataset is derived mainly from Tethyan locations. In this study, we examine marine sequences from the western margin of the North American continent and provide carbon isotope profiles from seven locatilies. One of them, the Ursula Creek section from Northeast British Columbia (Williston lake) is based on the analysis of organic matter, while all the other profiles were derived from carbonates from the Thaynes Formation outcropping in Western United States (NE Nevada, Utah and SE Idaho). The carbon isotope results show a series of large fluctuations throughout the early Triassic, that can be correlated with those previously reported from the Tethyan localities on the basis of existing biostratigraphical data. These findings confirm the global nature of the isotopic changes and, together with other geological observations, suggest that the perturbations in the global carbon cycle associated with the end Permian mass extinction did not stabilize before the Middle Triassic.