PHANEROZOIC ATMOSPHERIC OXYGEN: NEW RESULTS USING THE GEOCARBSULF MODEL

Modifications of the GEOCARBSULF model for Phanerozoic atmospheric oxygen have been made to account for new carbon isotopic data, reconsideration of the fractionation of carbon isotopes between carbonate and organic matter deposited in sediments, and different rates of weathering of volcanic rocks versus granitic rocks. Results indicate distinctly higher O(2) values than GEOCARBSULF for the Mesozoic and Cenozoic, lack of an appreciable drop in O(2) below 15 percent at any time, and a small late Cenozoic decline of O(2) to the present.