The Emporia Gazette

May 27, 2012

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What’s more fun than a box of rocks?

I’ll tell you: it’s seeing rocks in their natural environment out in the Flint Hills.

These stones have stories to tell. Well, the rocks don’t talk to me, but apparently they do have a lot to say to geologists.

It took a long time to get Kansas looking the way she does.

Oceans came and oceans went and the seas that covered Kansas left behind layers of stone. Limestone, which underlies the state, was created from the skeletons of marine organisms.

Now we’re talking a lot of time here. It was about 280 million years ago that the Permian Period seas floated over the land that is now Kansas.

A little more recently, on Sept. 22, Rex Buchanan and Bob Sawin of the Kansas Geological Survey led about 30 people on a geological hike at the Tallgrass Prairie National Preserve near Strong City.

Rex Buchanan is associate director for public outreach and Bob Sawin is a research associate for the geology extension. The KGS is located at the University of Kansas in Lawrence.

These men are familiar with the Tallgrass Preserve. They’ve both spent time here, walking the land to track down springs on the property.

On the geology hike, our first stop was at the 1881 farmhouse to examine Cottonwood limestone in the structure. Embedded in the stone are fusulinids: wheat-shaped fossils which were one-celled organisms.

Used as a diagnostic fossil, these fusulinids help date and identify stones. Cottonwood limestone is named after Cottonwood Falls. The names for geologic units are derived from the location where they are discovered.

There are many types of limestone. While walking in the Flint Hills, you may stumble across white stones with holes in them.

“The holes are one of the characteristics of Eiss limestone,” Sawin said. “A few years ago, we inventoried all the springs. Eiss had a lot of springs associated with it. The holes not only stored water but allowed it to move through.”

A core sample showed that the Eiss limestone contained gypsum, “which is real soluble,” Sawin said. “That explains the holes.”

As you look across the landscape, you can see a step-like aspect to the Flint Hills which is due to alternating layers of shale and limestone.

“The limestone is more resistant to weathering (than the shale),” Sawin explained.

Layered in with the limestone is chert (also called flint) which is even harder than the limestone.

“Chert has a very characteristic fracture pattern,” Buchanan told us. It has sharp-edged breaks; that’s why Native Americans used the stone for arrowheads.

In a road-cut along K-177, Buchanan pointed out brachiopod fossils in the limestone.

“You very seldom see these (fossils) whole,” he said. The high-energy environment of waves crashing upon a seashore tends to break up would-be fossils. “It’s a very tough environment for that kind of preservation.”

Buchanan mentioned transgression and regression of the seas. A number of oceans came and went, creating those layers of shale, limestone and chert. The waters would have been shallow and warm.

“We’re looking at a record of what the climate was like here,” Buchanan said of the geology.

“If you want to know what Kansas looked like 300 million years ago, go to the Caribbean,” he said.

So, in its past life, Kansas was like the Caribbean. Sigh. I was born 300 million years too late.

Kansas has a long and rocky history.

But our past is far from dull and dry. Once upon a time, Kansas was warm and wet and splashy.