Carbon and oxygen isotope data were obtained from the fine fraction and planktonic and benthic foraminifers from the Aptian-Albian sediments of the Ocean Drilling Program (ODP) Leg 192 at the Ontong Java Plateau (western equatorial Pacific). The 13C curves of these Ontong Java sections can be correlated to the composite 13C curve compiled from two sections in Italy. The difference in 13C between shallow and benthic carbonate was used in conjunction with the calcite compensation depth to estimate the atmospheric CO2 level during the Aptian-Albian interval according to Berger and Spitzy's (1988) method, and the CO2 estimated was ~8120 ppm for the Early Aptian, and ~1570 to 730 ppm for the Late Albian. The increase in atmospheric CO2 content as a result of the Ontong Java Plateau eruption (~1800 ppm) was also estimated from the degassing of basalt magma erupted. The 18O data were internally consistent in most cases, and were used to derive the average paleotemperatures during the Aptian-Albian (sea surface temperature: ~15-24°C after latitudinal correction). The relatively low paleotemperature estimates suggested that minor alteration might have occurred. Nevertheless, the temperature evolution trend had been largely preserved.
Reprinted with permission from the author.