The early Cretaceous was cold but punctuated by warm snaps resulting from episodic volcanism

Abstract

The Cretaceous is characterized as a greenhouse climate from elevated atmospheric carbon dioxide concentrations, transgressive seas, and temperate ecosystems at polar paleolatitudes. Here we test the hypothesis that the early Cretaceous was a cold climate state with a new Aptian atmospheric carbon dioxide record from the C3 plant proxy and early Cretaceous sea level curve from stable oxygen isotopes of belemnites and benthic foraminifera. Results show that carbon dioxide concentrations were persistently below 840 ppm during the Aptian, validating recent General Circulation Model simulations of ice sheets on Antarctica at those concentrations. In addition, sea level was estimated to be within the ice sheet window for much of the early Cretaceous prior to the Albian. This background state appears to have been episodically interrupted by Large Igneous Province volcanism followed by long-term carbon burial from weathering. We hypothesize that the early Cretaceous was largely an icehouse punctuated by warm snaps.