Terrestrial Evidence for Two Greenhouse Events in the Latest Cretaceous

Abstract

We present a terrestrial record of stable carbon and oxygen isotopes from paleosol carbonate for climate interpretations between ca.71.0 and 63.6 Ma.Isotopic ratios point to covarying and elevated atmospheric CO 2 pressures and temperatures between ca.70.0 and 69.0 Ma and ca.65.5 and 65.0 Ma.These two greenhouse episodes were characterized by atmospheric CO 2 levels between 1000 and 1400 ppmV (V = volume) and by mean annual temperatures in west Texas between 21 and 23 °C (~35°N paleo-latitude).Atmospheric CO 2 and temperature relations indicate that a doubling of pCO 2 was accompanied by an ~0.6 °C increase in temperature.A temperature gradient of ~0.4 °C per degree of latitude is proposed for North America across the Cretaceous-Tertiary boundary when comparing temperature proxies from west Texas with paleobotanical work in North Dakota.Our data demonstrate strong coupling between terrestrial climates and ocean temperatures that were possibly forced by Deccan trap volcanic degassing, leading to dramatic global climate changes.