Paleotemperature reconstructions from high Late Jurassic paleolatitudes

Mean belemnite delta18O values, derived from well preserved skeletal material, were -1.29‰ from DSDP site 330 and -1.45‰ from DSDP site 511. Assuming a seawater SMOW value of -1.0‰, mean palaeotemperatures calculated from the oxygen isotopic composition are 17.2°C and 17.9°C, respectively.

The inoceramid bivalves yielded much lighter delta18O values (mean -3.58‰). Petrographic and geochemical evidence points to the inoceramid bivalves being altered by diagenesis which accordingly accounts for the observed differences in isotopic values. "Vital effects" or the importation of belemnites or inocerarnids from another area, are considered not to account for the observed isotopic trends. The palaeotemperatures interpreted from the belemnites are significantly warmer than other recent estimates of Late Jurassic temperature (from oxygen isotope studies and climate model predictions) from similar southern palaeolatitudes.