Devonian Fossil Gorge – Coralville Lake, Iowa

devonian.jpg    Devonian Fossil Gorge – Coralville Lake, Iowa

Devonian Fossil Gorge – Coralville Lake, Iowa was discovered in 1993 when the flood abated, the eroded Gorge surface revealed a succession of 375 million year old bedding planes with diverse and abundant fossils commonly standing out in relief. Devonian Fossil Gorge soon emerged as the name for the feature.

Interpretive exhibits line the Entry Plaza, an open observation platform whose hexagonal outline reflects the symmetry of the abundant colonial coral Hexagonaria. Bedding plane bounded monoliths of Silurian Anamosa Stone dolomite that border the Plaza are 6 feet wide, 18 inches thick, and up to 15 feet high. Handicap-accessible walkways lead from the Entry Plaza to an adjacent Overlook Plaza, and down to the Biostrome Plaza near the Gorge floor. The Biostrome walkway is lined by a succession of 16 massive Cedar Valley slabs, taken from adjacent quarries, arranged in original stratigraphic succession. Construction of pathways within the Gorge has been avoided, but 20 “discovery points” are marked by numbered hexagonal metal plates: maps and explanatory brochures are provided.

Devonian Fossil Gorge is an invaluable resource for communication of the methodology of science. Evidence that the Midwest was once a shallow tropical sea, south of the Equator and teaming with life, can be presented convincingly, as can concepts such as geologic time and plate tectonics.

Location: Devonian Fossil Gorge is at the end of the Emergency Spillway at Coralville Dam, 2850 Prairie du Chien Road, N.E., Iowa City, Iowa

Phone: 319-335-1580 (Iowa Groundwater Association)

Open: Year around 


  1. I think this is a good article and it explains the history of the fossil gorge really well. I have been there once before and it is really neat I definetly reccomend going!

  2. Michael riley says:

    These six sided coral seem to be the same type of coral that is found at Petosky, Michigan.

  3. Michael riley says:

    Are other fossils present in Coralville, Iowa?
    Crinoid fossils for example lived in seawater.
    In 2011, I will visit and see these 375 million year old corals.

    I kind of understand 11,500 years old, because a glacier returned to WI and crushed a forest
    located about 2/3 of the way from Milwaukee to Green Bay. I just don’t get 375,000,000 years. I just cannot get my head around it.

  4. It truly is amazing, 350 million years! When you visit, this will be something you will remember and talk about for years!

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