Geologic Time & Ancient Environments

Time Travel through Turkey Run State Park's Past

by Deborah DeChurch, Erik Kvale, and Todd Thompson

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Rocky Hollow at Turkey Run State Park. Photo by Bill Stalions

Drive less than an hour west of Indianapolis, and you can stand in a steamy tropical swamp and watch dragonflies with two-foot wingspans buzzing above the fern-like trees. A six-foot-long millipede crawling through the mud passes by your feet.

In Indiana? Yes! That is, if you use your imagination to place yourself 300 million years into the geologic past when Turkey Run State Park was a sweltering insect-infested rain forest crossed by tidal creeks and estuaries. Imagine yourself in an area similar to the mouth of today's Amazon River where fresh-water rivers and streams meet the salty ocean. Giant rushes and now-extinct scaled trees line the coastline, and iguana-sized amphibians and sharp-toothed reptiles hunt for insects. Today, the sandstones and shales which make up the magnificent ravines along the park's trails are the remnants of the shorelines from this part of geologic time.

Whew! Now that you're overheated from hiking around in this tropical environment, time-travel forward 300 million years to the last Ice Age (10,000 years ago), and feel icy winds from a dirt-covered glacier chill you to the bone. Trumpeting herds of mammoths paw the tundra in front of the glacier looking for snow-covered grasses to eat. Pebbles, gravels, and dirt from bedrock of what is now the northern U.S. and Canada are left behind as the glacier melts. Today, we understand that Turkey Run's scenic ravines and canyons were carved by the forceful torrent of melting water from the glacier. In some of the streams of the park, you can see bowl-shaped potholes carved in the rock by current-driven pebbles and gravels swirling in depressions in the sandstone.

Once you get the hang of thinking in geologic time, it's fun to imagine what the world was like millions of years ago. Sherlock Holmes in hiking boots! Many of the remnants of ancient time are easy to find along the trails through Turkey Run. Look for seams of coal that were formed from the swampy jungles and fine layers in the lichen-covered sandstones formed by shifting sand bars in an ancient river. Human history is evident as well; you can learn about the ways that people used many of the resources there, such as quarrying the quartz-rich sandstone for use in glassmaking.

More information about Turkey Run State Park is availalbe in IGS publication SPG5, which also includes a topographic map of the park area.

Visit the Indiana Department of Natural Resources Web site at http://www.in.gov/dnr/parklake/properties/park_turkeyrun.html to read more about Turkey Run State Park.