Global trends of pCO(2) across the Cretaceous-Paleogene boundary supported by the first Southern Hemisphere stomatal proxy-based pCO(2) reconstruction

摘要

Reliable reconstructions of atmospheric carbon dioxide concentrations (pCO(2)) are required at higher resolution than currently available to help resolve the relationship between mass extinctions and changes in palaeo-pCO(2) levels. Such reconstructions are needed: 1, at a high temporal resolution for constraining the pre- and post extinction atmospheres; and 2, at a sufficient spatial resolution to constrain potential inter-hemispheric differences. Here we estimate pCO(2) based on fossil Lauraceae leaf cuticle specimens derived from three localities with strata spanning the latest Cretaceous to the mid-Paleocene, including a new Cretaceous-Paleogene boundary (K-Pg) locality, in New Zealand. We use two independent methods of stomatal density-based pCO(2) reconstructions; a transfer function calibrated using herbarium material and the stomatal ratio method, producing three calibration sets. Our results based on the mean values of each of the three calibration methods indicate pCO(2) ranging between ca. 460 and 650 ppm during the latest Cretaceous, falling precipitously to average values between ca. 360 and 430 ppm across the K-Pg boundary, and further to ca. 305-320 ppm in the mid-Paleocene. A 'spike' of extremely high pCO(2) at the K-Pg could not be confirmed, but our results are, nonetheless, consistent with previously published pCO(2) records from the Northern Hemisphere, and show that stomatal density worldwide was responding to significant changes in pCO(2) across the K-Pg. (C) 2016 The Authors. Published by Elsevier B.V.