INTERPRETING EARLY TRIASSIC (SMITHIAN) CLIMATE USING OXYGEN ISOTOPES OF CONODONT APATITE
The Smithian δ18O values range from ~14.4 to 17.6 ‰. In general, samples with low CAI values and smooth, non-pitted surfaces record higher isotopic values, while those with higher CAI values, pitted and/or secondary surface precipitates have lower isotopic values. Assuming conodonts with CAI values of ≤ 3 record primary/near primary seawater values and ice-free conditions, sea-surface temperatures from ~35 to 38 °C for the paleo-tropical and ~32 to 34 °C for the paleo-subtropical regions (Kolodny et al., 1983). These values indicate that the Smithian ocean was significantly warmer than the present oceans and were likely similar to the extreme greenhouse sea-surface temperatures calculated for mid- to late Cretaceous times.