Paleoclimate in the Wake of the K-Pg Extinction: Changes in Leaf Morphology and Carbon Cycling in the Early Paleocene of the Denver Basin, Colorado

The first million years of the Cenozoic Era encompass the initial recovery of the biosphere after the devastation of the K-Pg extinction. A stratigraphically constrained, expanded terrestrial section of the uppermost Cretaceous and lowermost Paleocene rock is present in the Denver Basin, Colorado, providing an extraordinary record of environmental change and ecological recovery in the aftermath of the extinction. This study constructs a paleoclimate record of this interval, and relates it to changes in the carbon cycle. Mean Annual Temperature (MAT) results from Leaf Margin Analysis from the first 850 ka after the K-Pg boundary were combined and correlated with Mean Annual Precipitation (MAP) estimates from Leaf Area Analysis conducted on 15 floral sites. These data were compared with carbon isotope ratios of bulk sediment analyzed from 28 discrete stratigraphic levels. The combined MAT and MAP records indicate that there were multiple temperature and precipitation shifts during the early Paleocene. Notably, the two lowermost of these events are each associated with significant changes in carbon isotope ratios. The isotopic event that occurs at the C29r/C29n boundary in the Denver Basin, Colorado is similar to those observed in some marine records, showing a possible terrestrial signal of the proposed "Dan-C2" event. These global teleconnections of the ocean-atmosphere system and their associated environmental changes in the wake of the K-Pg extinction provide further insight into the conditions under which the recovery of Paleocene ecosystems progressed.