OF-21-01 Geologic Map of the Barnesville Quadrangle, Weld County, Colorado


The purpose of this publication is to describe the geology, geologic resources, and geologic hazards of this 7.5-minute quadrangle. It is a continuation of field mapping work on the northern Front Range of Colorado where the CGS has cumulatively mapped 10 other quadrangles, this one extending the contiguously mapped area further east into the High Plains. CGS Geologists Kassandra Lindsey and Martin Palkovic completed the field work on this project during the mapping seasons of 2020-2021. Digital ZIP download. OF-21-01D

From the Geologic History:

The Southern Rocky Mountains bounds the western margin of the Denver Basin; the latter underlies much of the Great Plains physiographic province in north-eastern Colorado. The Barnesville quadrangle is situated within the Colorado Piedmont section of the Great Plains, approximately 80 km northeast of Denver and 50 km east of Fort Collins, Colorado. The Western Interior Seaway (WIS) occupied most of Colorado during the Late Cretaceous, depositing transgressive and regressive sedimentary rock sequences that underlie most of the map area. The early phase of the Laramide orogeny (~70 Ma) is correlative with the final stages of the WIS in the region. The Carlile Shale, Greenhorn Limestone, and Codell Sandstone (collectively known as the Colorado Group, map unit Kcgg), Niobrara Formation (Kn), and the Pierre Shale (Kp) record the final WIS transgressive and regressive marine sequences.