Pipe Creek Sinkhole preserves an ancient wetland. It was created by the collapse of a limestone cave in a Silurianreef formation. That left a steep-sided depression about 75 meters long, 50 meters wide and 11 meters deep. When water collected in the depression, it became the habitat of the plants and animals whose remains were preserved there when the sinkhole was buried by glacialoutwash and till during the Pleistocene Epoch, two million to 11,000 years ago.
While the ecology of the Pliocene in North America is well-known from fossil discoveries in other places, notably coastal sites, the Pleistocene glaciers destroyed or scattered most of the fossil remains in the continent's interior. Pipe Creek Sinkhole, however, was buried by the glaciers and the debris they left, making it the only known Pliocene example in the central part of the eastern half of the continent.
The sinkhole's ecology
A fossil pond turtle (center right) uncovered at Pipe Creek Sinkhole in 2003
Backed by a grant from the National Science Foundation, researchers from the Indiana State Museum and several universities substantially completed field work at the sinkhole in the summer of 2004, but the job of describing the fossils and determining their significance will take many years.
References
Farlow, James O. and Anne Argast, Preservation of Fossil Bone from the Pipe Creek Sinkhole (Late Neogene, Grant County, Indiana U.S.A.), Journal of the Paleontological Society of Korea, 22(1):51-75, 2006.
Farlow, James O. et al., New Vertebrate Fossils from the Pipe Creek Sinkhole (Late Hemphillian, Grant County, Indiana) Paper No. 7-1, delivered at Geological Society of America, North-Central Section - 38th Annual Meeting (April 1–2, 2004), St. Louis, Missouri.
Farlow, James O. et al., The Pipe Creek Sinkhole Biota, a Diverse Late Tertiary Continental Fossil Assemblage from Grant County, Indiana. American Midland Naturalist, 145:367-378.
Kash, Steve, Amazing Fossils: Grant County Discovery Reveals Life from 3-6 million years ago, Outdoor Indiana, March/April 1999.
Kash, Steve, Dr. Jack Sunderman Looks at Ancient River, Outdoor Indiana, November/December 2001.
Martin, Robert A., H. Thomas Goodwin and James O. Farlow, Late Neogene (Late Hemphillian) Rodents from the Pipe Creek Sinkhole, Grant County, Indiana. Journal of Vertebrate Paleontology 22(1):137-151, March 2002.
Sheets, Hope A., and James O. Farlow, Size-Frequency Distribution of Leopard Frogs (rana pipiens complex) from the Late Tertiary Pipe Creek Sinkhole, Grant County, Indiana, Paper no. 16-11 presented at the 37th Annual Meeting of the North-Central Section, Geological Society of America, 24-25 March 2003, Kansas City, Missouri.
Simo, J.A., and Patrick J. Lehmann, Diagenetic History of Pipe Creek Jr. Reef, Silurian, North Central Indiana, U.S.A., Journal of Sedimentary Research, 70(4):937, July 2000.
Sunderman, Jack A., Surprises in a Sinkhole, ACRES Quarterly, 42(3), Autumn 2003, published by ACRES Land Trust, Fort Wayne, Indiana.