Stable oxygen isotope chemostratigraphy and paleotemperature regime of mosasaurs at Bentiaba, Angola

Stable oxygen isotope values of inoceramid marine bivalve shells recovered from Bentiaba, Angola, are utilised as a proxy for paleotemperatures during the Late Cretaceous development of the African margin of the South Atlantic Ocean. The delta O-18 values derived from inoceramids show a long-term increase from -3.2 parts per thousand in the Late Turonian to values between -0.8 and -1.8 parts per thousand in the Late Campanian. Assuming a constant oceanic delta O-18 value, an similar to 2 parts per thousand increase may reflect cooling of the shallow marine environment at Bentiaba by approximately 10 degrees. Bentiaba values are offset by about +1 parts per thousand from published records for bathyal Inoceramus at Walvis Ridge. This offset in delta O-18 values suggests a temperature difference of similar to 5 degrees between coastal and deeper water offshore Angola. Cooler temperatures implied by the delta O-18 curve at Bentiaba coincide with the stratigraphic distribution of diverse marine amniotes, including mosasaurs, at Bentiaba.