DIVERSE EARLY PALEOCENE FOSSIL FLORA FROM THE OJO ALAMO SANDSTONE, SAN JUAN BASIN, NEW MEXICO, USA: IMPLICATIONS FOR LOCAL AND REGIONAL RESPONSES TO THE CRETACEOUS-PALEOGENE EXTINCTION EVENT
Fossil leaves were collected from the earliest Paleocene Ojo Alamo Sandstone, which corresponds with the Puercan 1 (Pu1) NALMA and was deposited in polarity C29r, indicating an approximate age of 66.0-65.7 Ma for these leaf localities. Fifteen leaf localities were collected, and census collections were made at 5 of the sites. The Ojo Alamo flora is dominated by angiosperms, relatively diverse, dominated by species that appear to be endemic to the SJB, and displays variability in morphotypes occurrences between facies. Leaf physiognomic paleoclimate analyses indicate the Puercan floras sample a warm and relatively wet climate, which remained similar throughout the early Paleocene. Interestingly, the SJB floras are significantly more diverse than age equivalent Northern Great Plains floras and indicate a warmer and wetter climate. These results indicate that a diverse and largely endemic plant community existed in the SJB within <~300 kyr of the K-Pg boundary. Further, these results demonstrate significant differences in species composition of northern and southern floras and a potentially large north-south diversity gradient, which suggests variable responses to the K-Pg extinction event across North America.