Notes on the Laramie Formation in Central Weld County, Colorado

Abstract

Several years ago while engaged in revising the geologic map of northeastern Colorado, there were discovered at two localities in the region of Laramie outcrop, horn cores and fragmentary limb bones of dinosaurs that strongly suggested Ceratopsian remains. The material, after preliminary study at the University of Colorado, was submitted to Dr. C. W. Gilmore of the United States National Museum for an opinion which verified the writer's determination of the horn cores as probable Triceratops remains. The limb bones are not sufficiently complete to be accurately identified, but the large size suggests that they too may be related to the genus Triceratops. One of the cores was found about two miles north of Briggsdale in central Weld County by Professor Henderson and the writer; the other some 12 miles northeast by a party under Mr. J. W. Vanderwilt of the Colorado Geological Survey. Inasmuch as identifiable dinosaur remains were previously unknown from the Laramie of the Denver Basin, the discoveries are of considerable interest because they suggest the correlation of the Laramie of eastern Colorado with the Lance formation of the Dakotas and Wyoming. In the early part of June of this year, Professor Henderson and the writer revisited the region near Briggsdale in an attempt to discover other remains and to locate those at hand definitely in the section as exposed in the area. Except for a small outlier of Oligocene (White River) beds on the higher areas north of Briggsdale, the surface of central Weld County is underlain by beds of Laramie age. The prevailing opinion has assigned a thickness of approximately 200 feet to the formation, but the recent investigation indicates the presence of about 400 feet of Laramie. The section consists of alternating sandstones, shales, lignitic shales, and impure