Named for Charles L. Pillmore, geologist with the U.S. Geological Survey. A specialist in the use of aerial photographs in geologic mapping, Pillmore is also an expert on the geology of the Raton Basin of Colorado and New Mexico, where he discovered the Cretaceous-Tertiary boundary claystone at about 20 different sites. Investigation of these sites has produced critical evidence that a large impact occurred at the end of the Cretaceous, coincident with a mass extinction of species. (M 17656) _ _.