GC1TKN8 The Ducey Stromatolite Locality
Type: Earth | Size: Other | Difficulty: | Terrain:
By: Me & Bucky @ | Hide Date: 06/12/2009 | Status: Available
Country: United States | State: Colorado
Coordinates: N40° 46.423 W108° 39.056 | Last updated: 08/30/2019 | Fav points: 0

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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: http://www.fossilmuseum.net/Tree_of_Life/Stromatolites.htm and http://www.fossilmuseum.net/Fossil_Galleries/StromatolitesAmerica2.htm

Cyanobacteria: Fossil Record. Online at: http://www.ucmp.berkeley.edu/bacteria/cyanofr.html

Early Life on Earth. Online at: http://www.wmnh.com/wmel0000.htm

Present-day Stromatolites from Shark Bay, Australia. Online at: http://everything-everywhere.com/2009/01/23/daily-travel-photo-shark-bay-australia/

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!

09/14/2018 By lesslost2
This EC almost achieves status as a bucket list component for us. When we saw that there were significant, even unique stromatolites to be seen, planning was on. We bought our first strom several years ago in Thermopolis, Wyoming, and have added considerably to that one since. Besides being dazzled by all the stroms to be seen at Ducey, we also took note of a piece of turritella agate nearby (reminiscent of Wamsutter, WY strata). We were further rewarded on the way in from US40 and on the way out by the large number of wild horses in the area (being provided water by a volunteer group in a heavy duty tanker). We have never been disappointed doing a "Me & Bucky" EC; thanks a bunch for this one.

10/01/2016 By k9jayhawk
Found with OF-Erad and Dustykat while touring NW CO. This cache was the highlight of the trip. The hike in and out was a bit strenous for us older guys but well worth it to see the geological history at this site...TFTC

10/01/2016 By OF-Erad

Found with K9jayhawk and DustyKat on another fun cache run. DustyKat e-mailed the answers for all of us. Thanks for placing this cache for us to find today. This is the most interesting earth cache I have ever found! TFTC!

10/01/2016 By DustyKat


We made the hike into this cache on Saturday October 1 2016 not expecting to find something this interesting and intriguing. I will in the future make a hike back here for a better look and better camera gear for more pictures. Favorite point for sure. Answers were emailed.

08/25/2012 By Denali41
Several years ago I became fairly familiar with the "roads" in this area when I was attempting to find my way in to the general vicinity of Vermillion Bluffs Badlands cache. It took me three attempts before I hit on an approach that actually worked, and the entire adventure remains one of my most memorable of my geocaching years. I discovered that I NEVER wanted to be on these "roads" when they are wet, or if there is any threat of rain! So it was with some trepidation that I began my journey in to this remarkable EarthCache while clouds were beginning to build. I went prepared, with shovel and jack and plenty of food and water and sleeping gear. But all turned out OK, and I was treated to a wonderful Me & Bucky educational experience and adventure. I knew nothing about stromatolites before reading the cache write-up and some of the supplemental materials. And then to see them in the field--these monsters that formed around algal masses stationed on what had once been rotted tree stumps. Now picture that scenario--trees out in this territory! And algae. How the world changes over geological time!

Well, I had a thoroughly enjoyable experience reaching and being at the Locality. And it was great to hike to the three Sites that needed to be visited. It was an eye-opener. And, of course, I was very happy to eventually get back to decent roadways after my excursion out to see these remarkable features was finally over. Thanks, Me & Bucky, for the experience! An e-mail will be sent with my specific answers.