Picket Wire Dinosaur Tracksite EarthCache
Hidden : 10/23/2008
Difficulty:
1.5 out of 5
Terrain:
4 out of 5

Size: Size: other (other)

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Geocache Description:


This EarthCache will take you to the Picketwire Canyonlands Dinosaur Tracksite, the largest dinosaur tracksite in North America. Withers Canyon is the only allowable access to the canyonlands for the general public. Parking can be found near N 37 39.584, W 103 34.251. Hiking, non-motorized bicycles, and horseback are the only allowable access. It is a minimum 11 mile round-trip from the parking area to the tracksite and back, with 500 feet of steep elevation change at the beginning and end of the hike. Once you reach the tracksite, you will need to cross the Purgatoire River, which may be ankle to waist deep. Know your limits and plan your hike carefully, as there is no overnight camping in the Picketwire Canyonlands. There is no drinking water available in the canyonlands, and at least one gallon of water per person should be taken with you. There is very little shade, so be prepared for the heat.

Picketwire Canyonlands is home to several rock art sites, as well as the Delores Mission and Cemetery. Please remember that cultural and paleontological resources on public lands are protected by law. Do not damage or remove cultural or paleontological resources. Making casts of the dinosaur tracks is not permitted without permission of the Comanche National Grasslands, U.S. Forest Service.

The Picktewire Canyonlands Dinosaur Tracksite is the largest dinosaur tracksite in North America. It is about one-quarter mile long and is located on both sides of the Purgatoire River in rocks of the Morrison Formation. The tracksite contains over 1300 visible tracks which make up over 100 distinct trackways. These prints were made by several species of dinosaurs, but were primarily made by two types: Allosaurus (or related theropods), and sauropods such as Apatosaurus (Brontosaurs).

About 60% of the tracks at the tracksite are from Allosaurus, a two-legged meat eating scavenger. These tracks consist of three narrow toes ending in a sharp point. Thin indentations formed from claws are often seen at the end of each toe.

Around 40% of the tracks are from Brontosaurs, four-legged plant eating sauropods. These tracks are very round in shape, with either no toes visible, or short stubby toes at the front end of the tracks. Several parallel trackways indicate that groups of younger Brontosaurs traveled as a group along the shoreline. This is the first evidence of social behavior among juvenile Brontosaurs found in the Morrison Formation.

These dinosaurs lived and walked along the edge of a large freshwater lake in what is now southeastern Colorado. As they walked through the mud and silt at the edge of the lake, their tracks were left behind. Fine silts and muds covered the tracks, and after being buried, the mudflats were turned to stone.

To log this EarthCache, send me an email with the answers to the following questions: 1.) How many million years ago did the dinosaurs inhabit the area that is now the Purgatoire River Valley? 2.) What has begun to erode the tracksite? 3.) What material is the Forest Service using to construct the erosion control structures to ensure the long-term preservation of the tracksite.

Please consider posting photos of yourself, or the local geology, when you log this EarthCache. Photos can be an additional rewarding part of your journey, but posting them is not a requirement for logging this EarthCache, and is strictly optional.

The above information was compiled from the following sources:

Interpretive Sign at Site.

Pike & San Isabel National Forests, Cimarron & Comanche National Grasslands Website: Picketwire Canyonlands Dinosaur Tracksite (visit link) and Comanche National Grassland – Picket Wire Canyon (visit link)

Santa Fe Trail Scenic and Historic Byway, The Mountain Branch. Website: Picket Wire Canyon on Comanche National Grasslands (visit link)

2000. Lockley, M.G. et. al. A Guide to the Purgatoire Dinosaur Trackway, Excerpts from the Book Dinosaur Lake, Special Publication 40, Colorado Geological Survey, 1997; in Field Trip Guidebook 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, La Junta and Trinidad, Colorado.

Thanks to the Comanche National Grassland for allowing placement of this EarthCache!

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