The Ducey Stromatolite Locality EarthCache
The Ducey Stromatolite Locality
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This EarthCache will take you to the Ducey Stromatolite Locality and is found northwest of Maybell Colorado. It is close to the badlands area near Lookout Mountain and the Vermillion Bluffs. In this three-part EarthCache, you will be looking at hundreds of examples of stromatolites, (in the form of concretions), which are the fossilized remains of microbial mats which formed in limestone- or dolostone-forming environments. You will be measuring some of these, so please bring a tape measure (a 15’ or 25’ tape works well) and be prepared to get dirty! Stromatolite localities are rather rare worldwide, and this one is of exceptional quality due to the size and number of well-preserved specimens. Because of the scientific importance of this site, please refrain from any collecting, including other geological material.
Access is by way of gravel and two-track roads which can become impassable if they are wet. A 4-wheel drive vehicle is required for access, and this is reflected in the terrain rating (not counting the 4-wheel drive vehicle, the terrain rating is a 3.5 – 4 for steep slope with decaying shale). Parking is at N 40 46.664 W 108 39.094, and care will need to be taken since this is next to a steep drop-off.
The Ducey Stromatolite Locality overlooks a steep drainage to Vermillion Creek, which runs into Irish Canyon and the Gates of Ladore. From the parking area, make your way down the hill southwards to the first set of coordinates.
Stromatolites are formed by the trapping and precipitation of particles by communities of microorganisms such as cyanobacteria and algae. Stromatolites are included among the oldest known fossils, and those from the Warrawoona Group in Western Australia are thought to be on the order of 3.5 billion years old! The stromatolites at this site are weathering out of a silicified limestone layer within the Laney Member of the Green River Formation, and are about 45-47 million years old. “Living” stromatolite communities are currently very rare, and exist in only a few localities worldwide.
Site 1 - N 40 46.423 W 108 39.056
This area contains hundreds of concretions that are weathering from a silicified layer of limestone. Most of the concretions range in size from 3 feet in diameter to 10 feet in diameter. The one at the given coordinates is one of the larger concretions, and the largest of all is 30 feet high and 20 feet across! These concretions formed around giant algal heads, which themselves formed about a forest of silicified rotted tree stumps.
Question 1. Measure the length, width, and height of this large egg-shaped stromatolite.
Site 2 - N 40 46.505 W 108 39.180
As you walk between the first and second set of coordinates, you will see several concretions that have weathered out of the Green River Formation and have begun to move down the hillside. Some of the more spherical and rounded of the concretions have made it to the creek bed below.
As you get closer to Site 2, you will see the layer of silicified limestone and its place on the hillside. Differential erosion has caused more of this layer to be exposed in some places than in others.
Question 2. Measure the height of the layer of silicified limestone at this location.
Site 3 - N 40 46.554 W 108 39.245
Walking along the stromatolite layer, you will see the wide variety of shapes that this locality has to offer. Spherical, cone-shaped, and egg-shaped, along with concretions that have weathered and begun to break down.
At the third set of coordinates, you will reach a large partially buried stromatolite that is almost perfectly spherical in shape. Answer one of the following two questions at this site:
Question 3a. Measure the diameter of this stromatolite and using the density of 2.4 g/cm^3 for silicified limestone, calculate its mass; or
Question 3b. According to research conducted on stromatolites which are actively growing in Australia, the growth rate of a stromatolite is approximately 0.5 mm/year. Assuming that this growth rate is constant, and that this is the rate at which this stromatolite grew, how long did it take the stromatolite at these coordinates to grow to this size?
To log this EarthCache, send me an email with the answers to these questions:
1.) Measure the length, width, and height of the egg-shaped stromatolite at the first set of coordinates.
2.) Measure the height of the layer of silicified limestone at this location.
3a.) Measure the diameter of this stromatolite, and calculate its mass; or tell me
3b.) How long did it take this stromatolite to grow to this size?
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:
Virtual Fossil Museum – Stromatolites. Online at: (visit link) and (visit link)
Cyanobacteria: Fossil Record. Online at: (visit link)
Early Life on Earth. Online at: (visit link)
Present-day Stromatolites from Shark Bay, Australia. Online at: (visit link)
1989. Kuntz, D.W., H.J. Armstrong, and F. J. Athearn. Faults, Fossils, and Canyons. Significant Geologic Features on Public Lands in Colorado. Geologic Advisory Group, Bureau of Land Management. Cultural Resource Series, Number 25.
Thanks to the Bureau of Land Management – Little Snake Field Office for allowing placement of this EarthCache!
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