Iowa's Devonian Fossil Gorge EarthCache
Iowa's Devonian Fossil Gorge
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The Devonian Fossil Gorge – A Window to Iowa’s Geologic Past
350 to 400 million years ago (give or take a week or two) all kinds of interesting creatures were happily enjoying the warm tropical sea in this area, filtering the water for food, resting on the seabed, swimming about and some even eating others.
In 1866, while digging the foundation for a new mill, strange coral formations were found, giving the name “Coralville” to the local town. By 1938, people living in the area had grown weary of the completely uncontrolled Iowa River, and the Army Corps of Engineers was given the task of moderating the flows. A large earthen dam was completed in 1958, creating Coralville Lake.
1993 brought record rainfall to the area, finally pushing the level of Coralville Lake over 712 feet above sea level, allowing a torrent of water to overtop the emergency spillway for 28 days. When the water finally receded, in places, up to 15 feet of topsoil and sediments below the emergency spillway had been washed way, exposing a large expanse of bedrock. Closer examination of this area showed this limestone bedrock to be an ancient sea floor, covered with millions of fossils of those creatures that inhabited the area 350 to 400 million years ago. This area was named “The Devonian Fossil Gorge” and in 2001, an outdoor interpretive facility was completed at the site.
In 2008, once again, record rainfall pushed the lake over the emergency spillway, this time to an even higher level, scouring the area below the spillway. Although parts of the interpretive facility were washed away or destroyed, the exposed area of bedrock was expanded, giving visitors to the site the opportunity to see additional fossil specimens.
Visiting the Devonian Fossil Gorge is a unique experience and hopefully those on a quest to log this Earth Cache will learn a bit more about the area in the process. To log this cache, please find the answers to the following questions and email them to me via Geocaching.com:
1) The listed coordinates will take you to the Entry Plaza. This area contains information about the site. One of these describes a “large armored fish” whose partial fossil was moved to the Visitors Center. What is this fish called?
2) This area of Iowa was once covered by a warm, shallow tropical ocean. What geological event(s) caused the area to slowly convert from an ocean to land now situated at an elevation of approximately 700 feet above sea level and over 700 miles from the nearest ocean?
3) Many of the “Discovery Points” placed at the site 2001 were washed away during the flood of 2008, however, one of these (Discovery Point 7 found at N41 43.368 W091 31.972) withstood the wrath of the flood and remains in place. Locate Discovery Point 7, tell what it refers to and if possible post a picture taken from this point looking down the gorge (away from the spillway).
3/3/09 - Unfortunately, it appears that Discovery Point 7 has been pilfered. Until this is replaced, you can find information on this point in the handout map of the area found on the temporary sign in the area. If possible, post a picture for the coordinates listed above.
4) For those die hards that absolutely need to sign a log book, one can be found in the Visitors Center (N 41 43.372, W 091 31.973) . Year round : Monday – Friday, 8:00 am – 4:00 pm. Saturday and Sunday (April 15 – October 15 only) 10:00 am – 5:00 pm.
This is a very unique area and should be treated with respect. As posted in the area, no fossils or rocks are to be removed from the area. Thank you to the area rangers and the U.S. Army Corps of Engineers for their work in maintaining this site.
Here is an interesting article done by Kaj O'Mara, Meteorologist with KCRG showing the effects of the flooding in 2008: (visit link)
Another point of interest here - if your GPSr has an altimeter and you are feeling a bit adventuresome, the top of the spillway is measured at 712 above sea level. If you wish to calibrate your altimeter, (carefully) climb to to top of the spillway (at your own risk, of course), and calibrate the altimeter with your GPSr laying on the very top of the spillway. Mine was off by 25-30 feet.
Thanks to drtmn for posting some great pictures. The one posted of an area that was cut out was actually a fossil specimen that was removed by the US Arm Corp of Engineers for further study and to preserve it from further weathering. These specimens are now located in the visitors center.
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