Climate, CO2 and correlation: A middle to Late Jurassic–Early Cretaceous carbon and oxygen isotope record

Carbon (δ 13 C organic , δ 13 C carbonate ) and oxygen (δ 18 O carbonate ) isotope records presented from DSDP Site 534A from the central Atlantic integrated with biostratigraphy, provides insights into the pattern of changes in carbon cycling, climate and ocean circulation. This study builds on the pioneering work of the DSDP, and utilises the extensive datasets published combined with new stable isotope data. We additionally examine the Jurassic/Cretaceous boundary to evaluate whether a distinct carbon isotopic pattern is observable. The dataset from Site 534A is one of the very few where long-term records of both δ 13 C carbonate and δ 13 C organic have been developed. These data from DSDP Site 534A record the temporal evolution of the carbon isotopes, together with oxygen isotopes that are interpreted as a temperature proxy. The Δ 13 C (i.e. the offset between δ 13 C carbonate and δ 13 C organic ) data are interpreted as a pCO 2 proxy. A Bathonian-Callovian δ 13 C carbonate and δ 13 C organic rise is followed by a Late Jurassic to earliest Cretaceous decline and the globally recognized isotopically positive event, the Weissert Event in the Valanginian. A distinctive δ 13 C carbonate and δ 13 C organic shift to more negative values in the mid-late Tithonian, the Volgian Isotopic Carbon Excursion (VOICE), as recognised elsewhere, is not identified. The δ 18 O record shows seawater temperature changes closely following the pCO 2 proxy record whereby rising pCO 2 and temperatures are seen in the Bathonian-Callovian, and occur in the early Valanginian. Temperatures and pCO 2 maxima occur the early Valanginian prior to the onset of the Weissert positive event. The inferred pCO 2 rise is coincident with the earliest Paraná-Etendeka volcanic phase.