Field trip no. 28 from “Geologic Excursions to the Rocky Mountains and Beyond,” field trip guidebook of the 1996 Annual Meeting of the Geological Society of America. Tertiary Igneous Rocks and Laramide Structure and Stratigraphy of the Spanish Peaks Region, South-Central Colorado: Road Log and Descriptions from Walsenburg to La Veta (Day 1) and and La Veta to Aguilar (Day 2). (SP-44 has the complete set.) 21 pages. Digital PDF download. OF-96-04-28D
Excerpted from the Introduction:
The Spanish Peaks are located in the western part of the Raton basin in south-central Colorado, southwest of Walsenburg. The two peaks, West Spanish Peak (WSP, 13,626 feet) and East Spanish Peak (ESP, 12,683 feet), are located on the upland part of the far western edge of the Great Plains physiographic region. East of Spanish Peaks, a deeply dissected plateau extends into the Great Plains.
The Raton basin, an asymmetric structure of Laramide age, underlies and surrounds the Spanish Peaks. The basin extends north from Ute Park, New Mexico, to Huerfano Park, Colorado. The juncture of steeply dipping western and gently dipping eastern limbs of the Raton basin forms the basin axis, known locally as the La Veta syncline. The La Veta syncline extends north-northwest into Huerfano Park, between the Sangre de Cristo and Wet Mountains.
These features and others such as the Laramide orogeny, igneous rocks, and an overview of petrology are discussed.