TIMING OF CARBON ISOTOPE EXCURSIONS DURING THE LATE TRIASSIC AND EARLY JURASSIC: NEW MODELING CONSTRAINTS FOR CARBON CYCLE PERTURBATIONS ASSOCIATED WITH THE EMPLACEMENT OF THE CENTRAL ATLANTIC MAGMATIC PROVINCE

A pronounced negative isotopic excursion in organic and inorganic carbon is coincident with the end-Triassic mass extinction, and a positive excursion follows during a period of initial recovery. The presence of these features is well established in many successions around the world; however, the temporal duration and causes of the isotopic excursions are not agreed upon. The changes in stable carbon isotopes during the late Triassic and early Jurassic are commonly linked to the emplacement of the Central Atlantic Magmatic Province via rapid input of CO₂. To better understand the effects of increased CO₂ on the biosphere, it is necessary to know the duration of the carbon cycle perturbations.

We measured organic carbon isotopes at the section near Levanto, Peru, and use the temporal framework provided by recent high-resolution biostratigraphy and ash bed dating (Schaltegger et al., 2008; Schoene et al., 2010; Guex et al., 2012; Wotzlaw et al., 2014). An initial positive excursion can be identified immediately followed by a negative excursion coincident with the last occurrence of Triassic ammonites, then an extended positive isotope excursion that persists through the onset of Jurassic ammonite recovery. This record is compared to existing data sets from Tethys and Panthalassa to distinguish local vs global CAMP effects. We temporally constrain the isotope excursions, and are able to compare and contrast these durations with those from modeled results.