THE PALEOCENE DINOSAURS OF THE SAN JUAN BASIN, NEW MEXICO: THE STRATIGRAPHER AND THE VERTEBRATE PALEONTOLOGIST SHOULD BE FRIENDS (PART TWO)

In his News in Depth comment “Does fossil site record dino-killing impact” (Science, 5 April, 2019, p. 10) Colin Barras writes “Geologists have theorized that the impact, near what is now the town of Chicxulub on Mexico's Yucatan Peninsula, played a role in the mass extinction at the end of the Cretaceous period, when all the dinosaurs (except birds) and much other life on Earth vanished. [my emphasis]”. In 2009, a paper by the author was published in Palaeontologia Electronica: “New geochronologic and stratigraphic evidence confirms the Paleocene age of the dinosaur-bearing Ojo Alamo Sandstone and Animas Formation in the San Juan Basin, New Mexico and Colorado.” This 146-page paper included a massive and detailed appendix on the palynology of the K-Pg boundary rocks in the San Juan Basin. These data showed that the dinosaur-bearing Ojo Alamo Sandstone was Paleocene in age throughout its extent in the San Juan Basin demonstrating that some dinosaurs in the San Juan Basin area survived the K-Pg asteroid-impact event. The value of palynologic data to help define the K-Pg boundary in the Western Interior of North America was first confirmed in the Raton Basin (230 km east of the San Juan Basin) where the actual fallout layer from the asteroid impact was found at multiple localities there. In fact, the fallout layer was first located in the Raton Basin based on palynologic data. The power of palynology to precisely locate and define the K-Pg boundary in the Western Interior of North America has been subsequently confirmed in numerous recent publications further supporting the palynologic Paleocene age determination for the dinosaur-bearing Ojo Alamo Sandstone in the San Juan Basin. Several papers, almost exclusively by a coterie of vertebrate paleontologists, have questioned the presence of Paleocene dinosaurs in the San Juan Basin, but none have provided one bit of evidence refuting the fact that the massive palynologic data base for the Paleocene age of the dinosaur-bearing Ojo Alamo Sandstone confirms its age. It is therefore frustrating to read commentaries, such as the one cited above in Science magazine, claiming that all dinosaurs became extinct at the end of the Cretaceous. Old paradigms die hard but is now past time for our geologic community to face the fact that some dinosaurs lived on into the Paleocene in the San Juan Basin.