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

2015; Cambridge University Press; Volume: 94; Issue: 1 Linguagem: Inglês

10.1017/njg.2015.1

1573-9708

C. Strganac, Louis L. Jacobs, Michael J. Polcyn, Kurt M. Ferguson, Octávio Mateus, António Olímpio Gonçalves, M.-L. Morais, Tatiana da Silva Tavares,

Isotope Analysis in Ecology

Abstract 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 δ 18 O values derived from inoceramids show a long-term increase from –3.2‰ in the Late Turonian to values between –0.8 and –1.8‰ in the Late Campanian. Assuming a constant oceanic δ 18 O value, an ∼2‰ increase may reflect cooling of the shallow marine environment at Bentiaba by approximately 10°. Bentiaba values are offset by about +1‰ from published records for bathyal Inoceramus at Walvis Ridge. This offset in δ 18 O values suggests a temperature difference of ∼5° between coastal and deeper water offshore Angola. Cooler temperatures implied by the δ 18 O curve at Bentiaba coincide with the stratigraphic distribution of diverse marine amniotes, including mosasaurs, at Bentiaba.