Butler County, Ohio - Prehistory


Butler County Before Man

Please be advised that much of the information here is still theory. I am presenting the most widely accepted theories here. There are other theories to consider.

Before the Ice Age

Ordovician Period

Butler County is in an area known to scientists as the Cincinnati Dome, a large area in North America defined by a bulging of the earth's crust into a dome shape. The elevation of this dome caused the oldest fossils to be found at the peak of the dome. The farther away from the peak, the younger the fossils are.

The bedrock under the majority of the county is from the Ordovician period of the earth's history. [MAP] It is believed that this period occurred 505-440 million years ago. Our county was completely submerged under a shallow sea during this time.

Although there were no land-dwelling animals or plants during this period, life was abundant in the sea! The sea was home to plant life, in the form of algae, and to aquatic animals. Isotelus brachycephalus, Ohio's oldest fossil, was a living trilobite in the sea that covered Butler County in that distant past. Isotelus is Ohio's official State Fossil. Trilobites were not alone in the sea. Other creatures included ostracods, the clam-like brachiopods, graptolites, corals, bryozoans, squid-like nautiloids, and jawless fishes called agnatha. Fossils of these earliest known Butler countians have been deposited in the bedrock that was formed during the Ordovician period.

Silurian Period

A very small section of Butler County is situated over bedrock from the Silurian period. This small area is along the central northern border of the county. [MAP] Scientists believe this period occurred approximately 438 to 408 million years ago. Ohio was located just below the equator at that time. The theory is that land creatures and plants appeared during the Silurian period. Insects were probably the first living creatures that were able to survive above water and appeared during this age. Ancient fish with jaws and backbones appeared.

Eventually the shallow sea drained from the land by an ancient river called the Teays River. This river was filled with deposits left by the Ice Age and the flow was diverted to the Ohio River.

The Ice Age

We have the Ice Age to thank for the fertile farmland that beckoned the earliest human settlers to Butler County. The Ice Age is more properly referred to as the Pleistocene Epoch and actually consisted of a series of successive glaciation periods alternating with periods of thawing. This was the most recent period of glaciations and occurred about 1.8 million-11,000 years ago. [MAP]

The repeated freezing and thawing, coupled with the grinding action of glacial flows, produced the deep and fertile Miamian soil predominant in this county.

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Last modified on Tuesday, 11-Sep-2018 01:01:01 MDT.