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Caesar Creek: Family Friendly Place to Fossil Hunt

Caesar Creek State Park - Near Waynesville, Warren County, Ohio ~ 449 to 445 Million Years Old
Upper Ordovician
Waynesville, Liberty, and Whitewater formations

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Why Are There Fossils Here? About the Geology of Caesar Creek

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.

Depositional Environments
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.

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References:

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

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Location: Where are the fossils - How to collect them

NOTE: Before collecting at the spillway, you must obtain a fossil collecting permit at the Visitor Center

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The visitor center (where the permits are) is marked on the google map below. 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! Be sure to go to the visitor center first for the permit.

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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!

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Rules:

These rules are listed on the fossil collecting permit:

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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.

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Fossil Identification: Fossils Found Here:

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Recommended Books about Ohio Fossils

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Fossils of Ohio (Bulletin 70)
By Rodney M. Feldmann (ed)
Copyright 1996
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.

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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!

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Ohio Rocks!
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.

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Recommended Fossil Clubs in the Area

Dry Dredgers

The Dry Dredgers is a Cincinnati based fossil club. Their club and website is a wonderful resource on fossils of ohio. They take regular field trips around the Cincinnati region, including Caesar Creek!

North Coast Fossil Club

This is another great fossil club based out of Cleveland. They also take regular field trips to fossil sites in and around Ohio.