Significant and Rare Paleontological Resources

Click on above image from the Denver Museum of Nature and Science to learn more.
About 65 million years ago, during the early Palocene epoch after the extinction of the dinosaurs, the area we now call Corral Bluffs was covered by subtropical forest. Palm trees were common, along with some rather modern deciduous trees.An ancient river flowed to the northeast and carved out the existing rock formations. The river and surrounding area were inhabited by ancient
Champsosaur fossil from the Royal Tyrrell Museum
turtles, fish and crocodiles.

Early Paleocene mammals drank at the river and lived nearby. Their brains were small and their teeth and limbs were not yet specialized. They were the ancestors of our present day deer, cattle, mountain lions, bears, coyotes, squirrels, mice and other mammals.

Since 1896, Corral Bluffs has been a significant area of study for paleontologists. A dozen mammal species have been found at Corral Bluffs, as well as fish, turtles, champsosaur and crocodiles. These fossils are in the Smithsonian, the Denver Museum of Nature and Science, the University of Colorado Museum of Natural History and other museums of note.

Fossil evidence from the Paleocene is scarce. Because of their small size, early mammal bones are not well-preserved in the fossil record. Most knowledge comes from fossil teeth and a few skeletons.

Phenacodus, a primitive ungulate (hooved mammal) about
5-1/2 feet long. Partial skeletal remains were found at Corral Bluffs.

As described by Kirk Johnson, Ph.D., Chief Curator and Vice President of Research & Collections at the Denver Museum of Nature and Science, Corral Bluffs is unique because it includes some of the most extensive surface exposures and badland outcrops in the Denver Basin. Because they're on private property they've not been fully explored, but explorations to date have shown that Corral Bluffs contains one of the three best exposures of the Cretaceous -Tertiary (K-T) boundary in the Denver Basin and one of the top 25 in the world. The K-T boundary is famous because it coincides with the extinction of the dinosaurs. See the black line pointed out on the map below.

Map courtesy of the Denver Museum of Nature and Science

See the article Corral Bluffs and the K/T Boundary - A Needle in the Haystack of Time from the Black Forest News 4/10/08 edition for more details and photographs

A 3/28/07 article in The Gazette says Dr. Kirk Johnson "thinks a student geologist came within about 10 feet of pinpointing the thin layer of clay known as the K/T boundary near Jimmy Camp Creek in the Corral Bluffs. That thin layer of clay separates two distinct periods of time on Earth — the Cretaceous, when dinosaurs lived and became extinct, and the Tertiary, which gave rise to the age of mammals. The boundary is so important because it is a precise marker in geologic time,” Johnson said. (link to Gazette article)

In 2000, The Denver Museum of Nature and Science (DMNS) excavated a nearly complete skull of an unnamed crocodile at Corral Bluffs (see below). They believe the potential for discovering more fossils of this type is high. An extremely rare fossil bird feather and highly unusual salamander footprints have been found. Corral Bluffs is the best site in Colorado and one of the top 20 sites in the world for mammals from the first 1 million years of the age of mammals.

Also exposed along the upper ledges of Corral Bluffs are dozens of large horizontal petrified logs ranging up to 4 feet in diameter and as long as 50 feet. Dr. Kirk Johnson says this represents one of the finest fossil forests in Colorado.

The DMNS recommends ongoing research, preservation of natural outcrops and exposed and buried fossils, and possible creation of guided trails, interpretive signage and even an interpretive center for the Corral Bluffs area. (link to letter from Kirk Johnson, Ph.D (pdf file).

Jaelyn Eberle, Curator of Vertebrate Paleontology at the University of Colorado Museum of Natural History (UCM) in Boulder writes, "These rocks in Corral Bluffs span the Cretaceous-Tertiary (K-T) boundary (65.5 million years b.p.), which marks one of the most important evolutionary events in the history of life - dinosaurs go extinct and soon after, mammals rapidly diversify and become larger. Very few places in the world preserve this explosive evolution of mammals wherein the roots of most modern mammalian groups were born. The Denver Basin, in particular Corral Bluffs, is one such place.

"Not only is this area rich with fossils, they are exquisitely preserved, a rare combination indeed in the world of paleontology! Understanding what happened amongst mammals following dinosaur extinction at the K-T boundary is critical to understanding the origins of modern mammals, including ourselves. Much of our knowledge of this important time comes from the fossil record in the Denver Basin, especially Corral Bluffs.

"If not collected properly and conserved, these fossils will be lost from scientific research and education. Given its natural beauty, unique fossils, and proximity to Colorado Springs, Corral Bluffs seems an ideal setting for educating students of all ages about the amazing prehistory of this region. Places like Corral Bluffs draw world attention to Colorado." (link to complete letter)

Jaelyn Eberle's article "Puercan mammalian systematics and biostratigraphy in the Denver Formation, Denver Basin, Colorado" published in Rocky Mountain Geology contains several references to fossils found at Corral Bluffs. See the abstract of her article.

Peter Robinson, Curator Emeritus at University of Colorado Museum supervised field work in the Corral Bluffs area during the 1970’s 80’s and writes, "The Corral Bluffs faunal sample is the only good record of that mammal age (early Paleocene; Puercan 2, in geologic terms) in Colorado. ... One can collect what is visible at the moment, but the next heavy rain may erode more of the outcrop and expose more fossil material. (link to complete letter)

In 2008, El Paso County Parks department hired an independent firm, SWCA Environmental Consultants, to do a brief paleontological survey of a portion of Corral Bluffs. Paleontology study PDF

They recommend a full paleontological survey and say, "Because of the abundance, diversity, and scientific importance of fossils in the Corral Bluffs area, together with the fact that it is the largest exposed sequence of late Cretaceous and early Tertiary rocks in the Denver Basin, mitigation strategies should include avoidance of highly fossiliferous areas, monitoring of construction excavations and salvage of scientifically significant fossils." Fossil occurrence is high and the rarely exposed K/T boundary and the property's extreme relevance to ongoing NSF-funded scientific research.

The paleontologists survey lasted only 5 hours (including hike to and from property) so they were only able to inspect the east-central portion of the property. They couldn't do stratigraphic positioning of the 9 fossil localities they found and it wasn't possible to develop meaningful development-specific mitigation options. No map was provided because fossil sites are protected by federal law.

SWCA Environmental Consultants saw abundant fossil wood, well-preserved logs, abundant leaves, twigs and roots. No vertebrate fossils were found, but given the limited time, this is not surprising. These fossils are often only discovered by screenwashing of bulk matrix samples. The previously recorded museum fossils indicate the virtual certainty that additional vertebrate fossils are present in the area. The primitive mammals fossils found at Corral Bluffs are rare examples of a critically important time in the evolution of mammals.

To read about the current paleontology and geology studies and see the latest fossil discoveries, visit Paleotrails Project, Colorado Springs, CO


Paleontology professor and students from the University of Wisconsin
A few of the fossils found
at Corral Bluffs
Partial skull of Periptychus, earliest Paleocene, dog-sized mammal that lived right after dinosaur extinction. Periptychus was an archaic ungulate or ‘condylarth’ and among the largest mammals of its time. They would have been in the first wave of mammals that appeared right after dinosaurs went extinct at the Cretaceous-Tertiary boundary.
Lower jaw (or dentary) of Periptychus
Lower jaw of Periptychus
Lower jaw of Ectoconus
Mammalian lower jaw fragment
Portion of ancient turtle shell before excavation
Interior of portion of ancient turtle shell after excavation
Exterior of portion of ancient turtle shell after excavation
Portions of another ancient turtle shell
Petrified tree roots
Petrified tree roots
65 million-year-old fossilized leaves
Shell fragment of a soft-shelled turtle (Trionychidae)
Fragment of vertebrate pelvic girdle
(hip region)
Pelvic or pectoral girdle
Ball of a femur or humerus
Crocodile humerus
Crocodilian osteoscute – one of the bones that sit in the skin on a crocodile’s back
Petrified wood
Petrified log