The Purgatoire River dinosaur trackway at twilight, Otero County, Colorado. Photo credit: Martin Lockley.

A Dash with Dinosaurs

2000-10-01 | CGS Admin

In the next months, we will be sharing some unpublished field trip guides that we have made over the years. The occasion for this one was “Earth Science Week” back in 2000, an annual event initiated by the American Geological Institute (AGI). That year, scores of celebrations—field trips, demonstrations, lecture series, film series, exhibits, school visits, and open houses—took place in all 50 states, as well as in Australia, Canada and at least 20 other countries. Eighteen AGI member societies and more than 100 state geological surveys, regional societies, academic geoscience departments, museums, libraries and federal agencies hosted these events. Thirty governors, the mayors of several cities and President Clinton issued proclamations and messages supporting the celebration of geoscience.

FT-00-03 A Dash with the Dinosaurs – A mountain bike trek to the Purgatoire River dinosaur trackway and a separate tour of the Cretaceous-Tertiary (K/T, known now as the K-Pg) Boundary impact layer of southeastern Colorado (La Junta and Trinidad), edited and compiled by Matt Morgan. PDF download.

From the Introduction to Part I: A Guide to the Purgatoire Dinosaur Trackway, Excerpt from the Book Dinosaur Lake

The Purgatoire River rises in the Rocky Mountains west of Trinidad, Colorado, and flows northeast across the southern High Plains for a distance of about 150 miles to its confluence with the Arkansas River just east of Las Animas. Although a sparsely populated and little known area, the Purgatoire Valley is one of the most beautiful locations on the High Plains. This guidebook will focus on the story of one small stretch of this valley known as Picket Wire Canyonlands, an area containing the largest dinosaur tracksite currently known in North America. The Picket Wire Canyonlands lie within the Comanche National Grasslands, approximately 23 miles south of the town of La Junta in southeastern Colorado. The area, currently managed by the USDA Forest Service, is rich in history, flora and fauna, and above all has a unique paleontological heritage. The tracksite is located in the northern portion of the Canyonlands, and the track-bearing rock is situated both within, and on the banks of the Purgatoire River.

From the Introduction to Part II: The K/T Boundary Impact Layer of Southern Colorado and Its Relation to the Chicxulub Crater, Mexico

Sixty-five million years ago a spectacular event occurred over what is now the Yucatan Peninsula of Mexico. An asteroid or comet slightly smaller than the size of Denver (~10 km), traveling at roughly 30 km/sec, slammed into the earth leaving a crater more than 150 km in diameter (Figure 1). The crater is now officially called Chicxulub (pronounced cheek-shoe-loob). Giant tsunamis over a kilometer high swept across the Yucatan Peninsula and the Gulf Coast causing massive destruction on land and triggering submarine landslides in the ocean (Alvarez, 1997). The ejecta, composed of pulverized and melted rock resulting from the impact, was launched like a bullet into and beyond the earth’s atmosphere. Some material came to rest around the circumference of the crater, forming an ejecta blanket hundreds of kilometers wide. The remaining material circled the globe and blocked sunlight, turning day into night. All was not over. As the ejecta rained down, friction heated the debris turning the atmosphere into an oven, baking the ground and everything on it and igniting the vegetation and forests. Soot from the fires added to the ejecta cloud that shrouded the earth (Alvarez, 1997). The surface of the earth was changed in an instant. Mammals took the place of the dinosaurs.

We also have a handful of copies left of the out-of-print SP-40 Dinosaur Lake: The Story of the Purgatoire Valley Dinosaur Tracksite Area written by Dr. Martin Lockley, one of a handful of global experts on dinosaur track sites.

The Purgatoire River dinosaur trackway at twilight, Otero County, Colorado. Photo credit: Dr. Martin Lockley.
The Purgatoire River dinosaur trackway at twilight, Otero County, Colorado. Photo credit: Dr. Martin Lockley.

Citations, Categories & Tags


Morgan, M. L., Christopher J. Carroll, and Joanna Wright. “FT-00-03 A Dash with the Dinosaurs – A Mountain Bike Trek to the Purgatoire River Dinosaur Trackway and the Cretaceous-Tertiary Boundary Impact Layer of Southeastern Colorado:” Colorado Geological Survey, Division of Minerals and Geology, Department of Natural Resources, October 2000.




2000s, Cretaceous, dinosaurs, field trip, fossils, POGI, Purgatoire, RockTalk, trackway