No Evidence for a Large Atmospheric CO2 Spike Across the Cretaceous
RESEARCH LETTER No Evidence for a Large Atmospheric CO2 Spike Across 10.1029/2018GL081215 the Cretaceous‐Paleogene Boundary Key Points: Joseph N. Milligan1,2 , Dana L. Royer1 , Peter J. Franks3 , Garland R. Upchurch4 , • Understanding atmospheric CO 2 1 across the Cretaceous‐Paleogene and Melissa L. McKee boundary has been limited due to 1 2 deficiencies in existing records Department of Earth and Environmental Sciences, Wesleyan University, Middletown, CT, USA, Department of Geology, • Our study highlights the utility of a Baylor University, Waco, TX, USA, 3School of Life and Environmental Sciences, University of Sydney, Sydney, New South proxy based on leaf gas exchange Wales, Australia, 4Department of Biology, Texas State University, San Marcos, TX, USA principles • We record a small transient rise in atmospheric CO2 that is more in line ‐ fi with modeled estimates of both Abstract Currently, there is only one paleo CO2 record from plant macrofossils that has suf cient Deccan volcanism and a bolide stratigraphic resolution to potentially capture a transient spike related to rapid carbon release at the impact Cretaceous‐Paleogene (K‐Pg) boundary. Unfortunately, the associated measurements of stomatal index are off‐calibration, leading to a qualitative interpretation of >2,300‐ppm CO2. Here we reevaluate this record Supporting Information: ‐ • Supporting Information S1 with a paleo CO2 proxy based on leaf gas exchange principles. We also test the proxy with three living species • Data Set S1 grown at 500‐ and 1,000‐ppm CO2, including the nearest living relative of the K‐Pg fern, and find a mean error rate of ~22%, which is comparable to other leading paleo‐CO2 proxies.
[Show full text]