Caesar Creek Spillway: Family Friendly Place to Fossil Hunt
Caesar Creek State Park - Near Waynesville, Warren County, Ohio
~ 449 to 445 Million Years Old
Waynesville, Liberty, and Whitewater formations
The Caesar Creek Spillway is full of Ordovician Fossils
A Beautiful Cincinnetina Brachiopod Fossil from the Caesar Creek Spillway
Why Are There Fossils Here? About the Geology of Caesar Creek
This map shows the Earth during the Ordovician time period. The approximate location of Ohio is marked by the star. It sits in a shallow sea along the continent Laurentia (which would become North America). Image modified from: Colorado Plateau Geosystems, Inc. [CC BY-SA 4.0]
The Caesar Creek Spillway was created by the U.S. Army Corps of Engineers to aid in flood control. When they blasted it out, they exposed layers upon layers of fossil bearing Ordovician limestones and mudstones that stretch for football fields!
Ohio in the Ordovician
During the late Ordovician, around 447 million years ago, most of North America, including Ohio, was covered by a shallow sea. Proto North America, or Laurentia, was just below the equator and experienced a very tropical climate.
Sediments would accumulate on the sea floor and eventually form the intermittent bands of shales/mudstones and limestones that we see today.
The mudstones represent deeper waters, while the limestones represent shallower waters (Hansen, 1997). Many of the thin limestone beds represent storm events where sediments washed in from the Taconic mountains to the east. These storm deposits are called tempestites (Hansen, 1997).
Over time, these sediments, along with any trapped and dead organisms, accumulated into deep layers. Pressure then turned these sediment layers into the mudstones and limestones we see today. Many of the organisms trapped in these sediments can now be found as fossils in these layers.
A Preserved Reef
The fossils record an ancient Ordovician reef system. Preserved in this reef are many types of corals, brachiopods (sort of like clams), trilobites, bryozoans, crinoids, and cephalopods. Although early jawless fish existed at this time, Hansen notes there are no recorded fish fossils from this area. He suggests since Ordovician fish fossils are found in nearshore environments elsewhere, the Cincinnatian rocks may have been too far offshore and therefore not the right environment for fish to inhabit (Hansen, 1997).
The Cincinnati Arch
Normally, these Ordovician rocks that are exposed all around Cincinnati would still be buried deep underground. However, during the Ordovician period, a volcanic island arc collided into Laurentia. This created the Taconic Mountains to the east. The Taconic mountain building event (Taconic Orogeny) caused buckling and folding of the Earth's crust. The area under Ohio buckled upwards. The whole Cincinnati region slowly uplifted, lifting these Ordovician rocks to the surface. This geological feature is called the Cincinnati Arch.
A closer map of Ohio showing the shallow sea and Mountains to the East Image from: Hansen, 1997 modified from Coogan, 1996.
Coogan, Allan H. (1996) Ohio's Surface Rocks and Sediments; Chapter 3 in Fossils of Ohio, edited by Rodney M. Feldmann; Ohio Geological Survey, Bulletin 70. Article Here
Hansen, Michael C. (1997) "The Geology of Ohio - The Ordovician" Ohio Geology, Ohio Division of Geological Survey, Fall. Article Here
Location: Where are the Fossils and how do I Collect them?
NOTE: Before collecting at the spillway, you must obtain a fossil collecting permit at the Visitor Center
The visitor center (where the permits are) is marked on the map. The actual spillway is just south of it, it's the large grey rectangle looking area. All of that grey is the Ordovician limestones and shales that contain fossils!
Caesar Creek Lake Visitor Center
Visitor Center Address: 4020 N Clarksville Rd, Waynesville, OH 45068
Hours: Mon-Fri: 8:00 - 4:00 , Sat-Sun: 8:30 - 5:00
Phone Number: (513) 897-2437 : You can always call before going to make sure their hours didn't change.
Visitor Center: How to get a Permit:
Caesar Creek State Park is a big park. The permits are at the Caesar Creek Lake Visitor Center. Be sure to go to the correct place, or you'll be driving around the lake for a half hour. The Caesar Creek Visitor Center is marked on the map above. It's just north of the Spillway.
Once there, simply go in and ask for a fossil hunting permit. They will go over all the do's and don'ts with you, you will initial it and sign off, then you can drive to the spillway to fossil collect. The US Army Corps of Engineers will also give you a nice little "Common Fossils" pamphlet that describes the types of fossils you will find.
When at the center, be sure to spend some time looking at all the Ordovician fossils. They have some nice displays!
The Fossil Permit and the "Common Fossils" pamphlet given to you when at the Caesar Creek Visitor Center
These rules are listed on the fossil collecting permit:
How to Look for Fossils
Since there are no tools of any kind permitted, looking for fossils is quite easy. Go slow, take you time, and walk or crawl around. You will find TONS of fossils. The key is to find nice specimens that are in palm sized rocks, so you can take them home!
I recommend fossil hunting here in the early spring. The winter freeze/thaw cycle tends to break up the rocks and freshly expose the fossils. By mid to late summer, the area becomes picked over until the next freeze/thaw cycle. Also, look closely, the trilobites here are "reduced" in size. In the rocks, the enrolled ones look similar to some of the tiny brachiopods.
The Fossil Hunting Area at the Caesar Creek Spillway
Fossil Identification: Fossils Found Here:
Below are common fossils found at the Caesar Creek Spillway. Click on any of them to go to the more detailed Identificaion Page:
Recommended Books about Ohio Fossils
Fossils of Ohio (Bulletin 70)
By Rodney M. Feldmann (ed)
State of Ohio Div. of Geological Survey
This book is a MUST for anyone collecting in Ohio or nearby Devonian formations. It has detailed descriptions and images of 100's of fossils one can find throughout Ohio, including the Cincinnati Arch. It can be ordered through the link above.
A Sea without Fish: Life in the Ordovician Sea of the Cincinnati Region (Life of the Past)
Life of the Past series: Richard Arnold Davis, David L. Meyer
Copyright 2009, Indiana University Press
This book gives a comprehensive view of life in the Ordovician seas. This wonderful introduction to the geology and paleontology of life in Ohio 450 million years ago is full of illustrations. If you have ever wondered what exactly the Ordovician of Ohio and the surrounding states looked like, this is your window!
By Albert B. Dickas
The author, a personal acquaintance of mine, is a Geologist that grew up in Ohio. His book is filled with beautiful pictures and wonderful information about Ohio's most interesting geologic sites. He does a great job writing these type of books. I recommend this book for anyone who lives in or is curious about Ohio's interesting geologic past.