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Pipe Creek Sinkhole

Grant County's Window into Indiana's Remote Prehistory

Overlook at Pipe Creek Junior Quarry
Photo courtesy of Professional Geologists of Indiana

Background: In 1996, workers at the Pipe Creek Junior limestone quarry near Swayzee, Ind., uncovered an amazing assemblage of fossils. Since the ancient sinkhole was first uncovered, researchers have discovered abundant plant and animal remains, including those of camels, bears, frogs, snakes, turtles and several previously unknown species of rodents. According to paleontologist James O. Farlow of Indiana University-Purdue University at Fort Wayne (IPFW), the five-million-year-old assemblage has yielded the first pre-glacial fauna from the age of mammals ever found in the interior of the eastern half of North America.

Text by Ed McDonald*
Past President, Three Rivers Gem and Mineral Society, Fort Wayne, Ind.

Grant County, Indiana To set the stage for the fantastic diversity of fauna (animal) and flora (plant) fossils located in "the sink," we need to go back in geologic time to the Paleozoic Era (570 to 280 million years ago). This era consisted of six periods:

  1. 1. the Cambrian (570 to 505 million years ago) saw the beginning of complex life forms including sea plants and shelled animals, the most notable being trilobites;
  2. the Ordovician (505 to 438 million years ago.), the dominant forms were brachiopods, bryozoans and crinoids, and land plants became established;
  3. the Silurian (438 to 408 million years ago) saw land plants flourish and the growth of major reefs in warm, shallow tropical waters;
  4. the Devonian (408 to 360 million years ago) was the age of fishes and saw the deposition of reefs and all their diversity now in evidence at the Falls of the Ohio River;
  5. the Carboniferous (360 to 286 million years ago) worldwide, in North America subdivided as
    • the Mississippian: the beginning of amphibians; and
    • the Pennsylvanian: the development of trees and the expansion of areas of tropical swamps dominated by huge fern plants that gave us our present-day coal deposits; and
  6. the Permian (286 to 245 million years ago): the age of reptiles and the precursors to dinosaurs.

    The Paleozoic started as a warm interval following an ice age and the first of three major mass extinctions. These mass extinctions separate the three eras: Paleozoic ("ancient life"); Mesozoic ("middle life"); and Cenozoic ("recent life"), the era in which we live, which has seen two periods:

    1. the Tertiary (66.4 to 1.6 million years ago - the Pipe Creek fossils are from late in this period); and
    2. the Quaternary, our own period.

    reef dolostone, IPFW GeoGarden In the Silurian Period, what is now Indiana and the interior of North America was located south of the equator and enjoyed warm tropical weather. The interior of the continent was a warm, shallow sea that supported the diverse tropical reef ecosystem. The organisms in this reef deposited huge amounts of calcium carbonate that compacted into limestone. The northern portion formed the Fort Wayne Bank that extends from northwestern Ohio to southern Lake Michigan. (The stone at right comes from an exposed portion of the bank at the May Stone and Sand quarry in Allen County.) To the south, the Terre Haute Bank formed, separating the Cincinnati Arch from the Illinois Basin, giving rise to deposits that became the coal seams of southern Illinois and southwestern Indiana. All this time, North America was drifting northward toward its present location on the globe. Over time, water percolated through the limestone, forming numerous caves and caverns, as evidenced in the karst area of southern Indiana and central Kentucky.

    The Sinkhole: Origins and Importance

    The Permian Period ended with a "greenhouse" interval that saw another mass extinction and ushered in the Mesozoic Era, noted for the rise of the dinosaurs. Birds and mammals developed, but did not become dominant until after the mass extinction of the dinosaurs that ended the Mesozoic 65 million years ago. During this time, the continent continued to move north, and the caves in the limestone of the old Silurian reef became larger and more numerous. The collapse of one of these caves created the Pipe Creek Sinkhole, a water-filled depression that attracted an amazing diversity of animals in the Pliocene Epoch, 7 to 2 million years ago, the last of the five epochs of the Tertiary Period.

    The diverse ecology of the Pliocene is well-known from fossil discoveries in many locations. 1, 2. However, Pipe Creek is the only known example in the central part of the eastern half of North America. The sinkhole today is exposed in the Pipe Creek Junior Quarry, operated by Irving Materials, Inc., near Swayzee in Grant County (see map). It is about 75 meters long, 50 meters wide and 11 meters deep, with steep sides. At the bottom are stream and pond sediments covering the collapsed cave roof that rests on Silurian bedrock. This layer of sediment contains the Pliocene fossils.

    Above Left: The exposed sinkhole. The original depression is still visible.
    Above Right: Oxidized limestone below the feature shown at left is a remnant of the sinkhole.
    Photos courtesy of Professional Geologists of Indiana.

    Above Left: Another view of the exposed sinkhole. Above Right: Excavated pond turtle shell.
    Photos by Ed McDonald.

    Abundant quartzite pebbles from the stream deposit have been traced to the headwaters of the ancient Teays River in the Appalachian Mountains. Buried by glacial deposits, the Teays drained much of this part of the continent before the Ohio existed and passed a few miles north of the sinkhole. Noting that the buried Teays bedrock is some 400 feet lower than the sinkhole, Jack A. Sunderman, IPFW Emeritus Professor of Geology, concludes that if the Teays is the source of the pebbles, then "it must have transported and deposited them on an upland surface before the downcutting of the now-buried Teays Valley began!"

    Above these deposits a wetland formed with a large and dense plant and animal population. The climate was warm and temperate, but somewhat dry, possibly supporting a "parkland" ecology, a grassland-forest transitional zone. It is the deposits from this wetland that have yielded the fossil assemblage that is unique to Pipe Creek. The fossiliferous deposit was covered by glacial outwash and till in the Pleistocene Epoch, 2 million to 11,000 years ago. The vertebrate fauna preserved is dominated by aquatic species, particularly leopard frogs. Mammalian finds include an early rhinoceros (Teleoceras), canids (related to dogs), peccaries (similar to pigs) and short-faced bear.

    In addition to Jim Farlow, Pipe Creek researchers include Ron Richards of the Indiana State Museum, J. Alan Holman of Michigan State University, Bob Martin of Murray State University in Kentucky and Anthony Swinehart of Hillsdale College in Michigan. Funded by a National Science Foundation grant, regular field work at Pipe Creek continued through 2005, but a weeklong dig has usually been conducted every year since. The toe bone of a young camel was uncovered in 2011; and pieces of the jawbone of a hyena-like canid were found in 2014 during what probably will be the last year of field work at the site. A taxonomic list of species discovered at Pipe Creek may be found in The Paleobiology Database.

    Summary: The collapse of a cave in limestone that was once a Silurian coral reef created a steep-sided depression that filled with water from the now-vanished Teays River. During the Pliocene Epoch, roughly five million years ago, the waterhole attracted wildlife from the drier surrounding area. Some of the plants and animals that died there were preserved as fossils in the sediments. During the glaciations of the Pleistocene, the entire assemblage was buried, preserving it as a unique record of life in eastern North America before the Ice Age.

    References and Additional Reading

    Ault, Curtis H., et al., 1987. Map of Indiana showing thickness of Silurian rocks and location of reefs. Indiana Geological Survey/Dept. of Natural Resources, Map #54.

    Ault, Curtis H., 1992. Exposure of Silurian Reefs in Indiana. Indiana Geological Survey Occasional Paper #61.

    Bevington, Cindy, 2003. History Unearthed: Paleontological dig fills a gap in prehistoric Indiana, The Evening Star (Auburn, Ind.) 15 June 2003, p. C1.

    Bleuer, N.K., 1989. Historical and Geomorphic Concepts of the LaFayette Bedrock System (So-called Teays Valley) in Indiana. Indiana Geological Survey Special Report #46.

    Bleuer, N.K., 1991. The Lafayette Bedrock Valley System of Indiana: Concept, Form, and Fill Stratigraphy, pp. 51-77 in W.N. Melhorn and J.P. Kempton (eds.), Geology and Hydrology of the Teays-Mahomet Bedrock Valley System. Geological Society of America, Special Paper #258.

    Breen, Ed, 2004. Digging Up Indiana's Past: Grant County Sinkhole is Time Capsule. The Journal Gazette (Fort Wayne, Ind.) 5 July 2004, p. 1C.

    Esarey, Ralph E., and D.F. Bieberman, 1949. Silurian Formations and Reef Structures of Northern Indiana. 3rd Annual Indiana Geologic Field Conference, 13-15 May, 1949.

    Farlow, James O. et al., 1997. The Pipe Creek Sinkhole Biota, a Diverse Late Tertiary Continental Fossil Assemblage from Grant County, Indiana. American Midland Naturalist, 145:367-378. (Note literature cited as additional technical references.) Abstract

    Farlow, James O. et al., 2004. New Vertebrate Fossils fom 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 12, 2004), St. Louis, Mo. Abstract

    Farlow, James O. and Anne Argast, 2006. 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. Full text

    Farlow, James O. et al., 2010. Coprolites from the Pipe Creek Sinkhole (Late Neogene, Grant County, Indiana, U.S.A.), Journal of Vertebrate Paleontology, 30(3):959-969. Abstract

    Farlow, J.O., Argast, A., Sunderman, J.A., 2010. Geology of the Late Neogene Pipe Creek Sinkhole (Grant County, Indiana), Indiana Geological Survey Special Report 69. Full text

    Kash, Steve, 1999. Amazing Fossils: Grant County Discovery Reveals Life from 3-6 million years ago. Outdoor Indiana, March/April 1999.

    Kash, Steve, 2001. Dr. Jack Sunderman Looks at Ancient River. Outdoor Indiana, November/December 2001.

    Kilbane, Kevin, 2003. Picturing Prehistoric Life: Quarry's fossils could help solve a 5-million-year-old mystery. The News-Sentinel (Fort Wayne, Ind.) 4 July 2003, p. 1F.

    Kurtz, David, 2002. Rhinoceroses Once Roamed Indiana: Auburn Professor Sifts 5-Million-Year-Old Fossils. The Evening Star (Auburn, Ind.) 8 June 2002, p. 1A.

    Lutgens, Frederick K., and Edward Tarbuck, 1995. Essentials of Geology (5th ed.), Illinois Central College/Prentice Hall, Inc., Division of Simon and Schuester Co.

    Martin, Robert A., H. Thomas Goodwin and James O. Farlow, 2002. Late Neogene (Late Hemphillian) Rodents from the Pipe Creek Sinkhole, Grant County, Indiana. Journal of Vertebrate Paleontology 22(1):137-151, March 2002. Abstract

    Plummer, Charles C. and David McLeary, 1996. Physical Geology (7th ed.), California State Univ. at Sacramento/Wm. C. Brown Publishers (Times-Mirror Higher Education Group).

    Sharma, Rekha. 2004. Series of articles on 2004 dig at Pipe Creek Jr. quarry. The Chronicle-Tribune (Marion, Ind.) 18, 19, 24 June 2004.

    Shaver, Robert H., et al., 1978. The Search for a Silurian Reef Model in Great Lakes Area. Indiana Dept. of Natural Resources/Indiana Geological Survey Special Report #15.

    Sheets, Hope A., and James O. Farlow, 2003. 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. Abstract

    Sheets, Hope A., James O. Farlow, Blaine W. Schubert, and Steven C. Wallace, A Paleoecology Comparison Study of Anurans from the Gray Fossil Site, Washington County, TN, and the Pipe Creek Sinkhole, Grant County, IN (presentation at Geological Society of America, Southeastern Section, 55th Annual Meeting (2324 March 2006). Abstract

    Shunk, Aaron J, Steven G. Driese, James O. Farlow, Michael S. Zavada and Mohamed K. Zobaa, Late Neogene paleoclimate and paleoenvironment reconstructions from the Pipe Creek Sinkhole, Indiana, USA, Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 274, Issues 3-4, 15 April 2009, Pages 173-184. Abstract

    Simo, J.A., and Patrick J. Lehmann, 2000. Diagenetic History of Pipe Creek Jr. Reef, Silurian, North Central Indiana, U.S.A. Journal of Sedimentary Research, 70(4):937, July 2000. Abstract

    Sunderman, Jack A, 2003. Surprises in a Sinkhole, ACRES Quarterly, 42(3), Autumn 2003, published by ACRES Land Trust, Fort Wayne, Ind.

    Sunderman, Jack A. and E. Troy Rasbury and Sidney R. Hemming, submitted January 2003, Blue Ridge Provenance of Metaquartzite Pebbles from Northern Indiana, from Pb/Pb Quartz Ages and Petrographic Constraints: Implications for Midwest Tertiary Drainage History: Journal of Sedimentary Research.

    Troutman, Grant, "Ancient Bones Still Thrill," The News-Sentinel (Fort Wayne, Ind.) 1 July 2011.

    In Memoriam
    Ed McDonald

    Ed McDonald, the co-creator of this site, died at his home in Auburn, Ind., Feb. 10, 2013, at age 74. He will be greatly missed.


    Location of Pipe Creek Sinkhole
    Indiana Geologists
    Indiana Geological Survey
    Gray Fossil Site
    IPFW Geosciences
    Pipe Creek Sinkhole Project
    Animals of Pipe Creek Sinkhole
    Professional Geologists of Indiana
    Three Rivers Gem and Mineral Society
    Fossil feces from an Indiana sinkhole

    *The late Ed McDonald, a retired police officer for the City of Auburn, Ind., was an amateur geologist.
    **Page layout by Mike Walter.
    ***Ed and Mike are grateful to Jim Farlow for his help.

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    This page was published on May 22, 2003. It will be updated as new information becomes available.
    The most recent update was October 22, 2014.

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