Carbon cycle changes during the Triassic-Jurassic transition

摘要: The end-Triassic is regarded as one of the five major mass extinction events Phanerozoic. This time interval marked by up to 50% marine biodiversity loss and changes in terrestrial ecosystems. Mass are often global carbon cycle. reality nature C-cycle at Triassic-Jurassic (T-J) transition however questioned its causes poorly understood. Potential sizes fluxes between exchangeable reservoirs, reflected isotopic composition these reservoirs. Several geological outcrops, representing T-J transition, have been studied Northern Calcareous Alps (Austria). Sediments sections were deposited intra-platform Eiberg Basin that extended for several hundreds kilometers on continental margin north-western Tethys Ocean. High resolution C-isotope studies this basin showed a 5-6‰ isotope excursion (CIE), which directly preceded last occurrence typically Triassic ammonites succeeded first Jurassic pollen. strongly suggests simultaneous event negative CIE. Compound specific delta 13C measurements plant-wax derived n-alkanes also show ~6‰ together with event. It cycle caused depleted release atmosphere. These attributed increased volcanic CO2 emissions related break-up Pangaea, emplacement Central Atlantic Magmatic Province. duration activity boundary confined ~600 kyr. Alternations relative abundance limestone versus marl black shale deposits, observed uppermost lower shallow sedimentary succession St. Audrie’s Bay East Quantoxhead (southwest UK). Spectral analyses high (‰), TOC (%) CaCO3 (weight %) proxy-records from sections, suggest astronomically controlled variations climate palaeo-environment. allows confining subsequent recovery Hettangian stage ~20-40 kyr, ~140 kyr ~1.8 Myr, respectively. short coinciding CIE do not match tuned activity. Simple balance calculations perturbation best explained rapid massive ~7000 Gt isotopically methane-hydrate reservoir. research causal relationships release, change highly biodiversity-loss. However, levels did only increase Rhaetian. Also late already enhanced both realm. study shows late-Rhaetian two CIEs proxy-records, suggesting depletion Oxidation organic subsurface thermal metamorphism rich strata may be potential mechanism transfer light exogenic pool.