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Mazon Creek fossil beds

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Title: Mazon Creek fossil beds  
Author: World Heritage Encyclopedia
Language: English
Subject: Geography of Grundy County, Illinois, Paleozoic paleontological sites of North America, Burpee Museum of Natural History, Belotelson, Fossil
Collection: 1997 in Paleontology, Carboniferous Illinois, Carboniferous Paleontological Sites, Geography of Grundy County, Illinois, Lagerstätten, National Historic Landmarks in Illinois, National Register of Historic Places in Illinois, Natural Features on the National Register of Historic Places, Natural History of Illinois, Paleontological Sites of North America, Paleontology in Illinois, Paleontology in the United States, Paleozoic Paleontological Sites of North America, Protected Areas of Grundy County, Illinois
Publisher: World Heritage Encyclopedia

Mazon Creek fossil beds

Mazon Creek fossil beds
Stratigraphic range: Pennsylvanian
Mazon Creek Fossil Beds
Nearest city Benson Road, Morris, Illinois
Governing body Private
NRHP Reference # 97001272
Significant dates
Added to NRHP September 25, 1997[1]
Designated NHL September 25, 1997[2]
Tullimonstrum gregarium in a concretion from the Mazon Creek lagerstätten.

The Mazon Creek fossil beds are a conservation lagerstätte important to paleontologists, in attempting to reconstruct the paleoecology of the sites.[3] The locality was declared a National Historic Landmark in 1997.[2][4]


  • Geology 1
  • Location 2
  • Flora 3
  • Fauna 4
    • Essex Biota 4.1
    • Braidwood Biota 4.2
  • See also 5
  • References 6
  • Further reading 7
  • External links 8


The Mazon Creek fossils are found in the Upper Carboniferous Francis Creek Shale;[5] the type locality is the Mazon River (or Mazon Creek), a tributary of the Illinois River near Morris, Grundy County, Illinois. The 25 to 30 meters of shale were formed approximately , during the Pennsylvanian period. The fossiliferous concretions are usually found within the thickest deposits of Francis Creek. The concretions occur in localized deposits within the silty to sandy mudstones, in the lower four metres of the formation. The paleoecosystem is believed to be a large river delta system, deposited by at least one major river system flowing from the northeast. The sediments are believed to derive from the Appalachian orogeny events. The delta had a tropical climate, a result of the area being within 10° north latitude of the equator during the Pennsylvanian.

The remains of plants and animals were rapidly buried by the sediment deposited in the deltaic system. Bacterial decomposition of the remains produced carbon dioxide that combined with dissolved iron from the groundwater. This process formed siderite in the sediments surrounding the remains, forming detailed casts of their structure. Lithification of the sediments formed protective nodules of ironstone around the now fossilized remains. This mode of preservation is known as authigenic mineralisation.


The fossiliferous concretions are found in the Mazon River area of Grundy, Will, Kankakee, and Livingston counties. Additional fossils are found in LaSalle County, Illinois; between the Vermilion River and Marseilles, Illinois. The ironstone concretions are recovered from exposures along streams, roadcuts and in active or abandoned coal mine areas.

Most concretions are found among the shale and sandstone that was piled up in either a spoil tip of an older underground mine, or ridges of the later surface mining. The Peabody Energy company operated several large strip mines in Grundy County that are now abandoned. They were named Pit 1 through Pit 11. The northern pits 1-8 are known for the Braidwood Biota with mostly terrestrial fauna and flora. Pit 11, which was located southwest of the town of Braidwood, Illinois, is known for its Essex Biota with a greater abundance of marine species.[6] Pit 11 is now Braidwood State Fish and Wildlife Area, an Illinois state park. Fossil collecting is allowed at the park with a permit.[7]

The site's importance was realized in the mid-nineteenth century: "the nodules of Mazon Creek, where fragments of plants, even of the softest texture, have been preserved in their integrity".[8]


The Mazon Creek flora comprises over 400 species from at least 130 genera. However, the true number of species is difficult to determine. Paleobotanists name separate plant structures with different names by convention, inflating the number of fossil plant taxa. Paleobotanists are currently determining which taxa are valid.

Mazon Creek flora includes: lycopsids, related to modern club moss, with arborescent forms named Lepidophloios, Sigillaria and Lepidodendron, and herbaceous forms called Lycopodites and Cormophyton; sphenopsids like Calamites a tree-like horsetail relative, with common foliage names of Annularia and Asterophyllites, and a vine-like form called Sphenophyllum; Pteridophyta as marattitalean tree ferns and Filicales and Zygopteridales understory ferns, with common foliage names of Pecopteris, Acitheca and Lobatopteris; pteridosperms, also known as seed ferns, an extinct group of plants that grew both as trees and smaller shrubs, with features like pinnated leaves similar to true ferns, but reproduced by seeds instead of spores; they had common foliage names Mariopteris, Alethopteris, Odontopteris, Neuropteris, Laveineopteris and Macroneuropteris; extinct gymnosperm Cordaites, believed to be closely related to and sharing many features with modern conifers.


Bandringa rayi fossil shark, Mazon Creek Lagerstatte. This is the holotype specimen of the species. Its size and lack of developed cartilaginous skeletal structures indicate that this is a juvenile shark.

The Mazon Creek fauna has over 320 species of animals that have been identified. The fauna is divided into two components: the marine Essex fauna and the land and freshwater Braidwood fauna, that were washed into the deltaic sediments.

Essex Biota

The Essex fauna includes crustacean Belotelson and the possible hemichordate Etacystis.

Braidwood Biota

The Braidwood fauna includes insects, millipedes, centipedes, scorpions, spiders, other arachnids, amphibians, freshwater fish, freshwater shrimps, freshwater horseshoe crabs and ostracods. The oldest known beetle has been described from the Braidwood fauna.[9]

Three species of centipede have been described from Mazon Creek. They are known from around 60 specimens in total, and belong to three species:[10]

Fossil centipedes are very rare, and Mazoscolopendra and Palenarthrus are the only known Paleozoic scolopendromorphs.[11]

See also


  1. ^ "National Register Information System". National Register of Historic Places.  
  2. ^ a b "Mazon Creek Fossil Beds". National Historic Landmark summary listing. National Park Service. Retrieved 2007-10-11. 
  3. ^ Illinois State Museum-Mazon Creek Fossil Exhibit
  4. ^ Joanne Klussendorf (March 30, 1995), National Historic Landmark Nomination: Mazon Creek Fossil Beds (pdf), National Park Service . Accompanying photos, from 1912 and 1991. PDF (497 KB)
  5. ^ a b P. A. Allison (1987). "A new cephalopod with soft parts from the Upper Carboniferous Francis Creek Shale of Illinois, USA".  
  6. ^ a b Selden, Paul; Nudds, John (2012). "Mazon Creek". Evolution of Fossil Ecosystems (second ed.). Manson Publishing Ltd. pp. 94–96.  
  7. ^
  8. ^ A.H.W. in Geological Survey of Illinois, 1866, p 489
  9. ^ Oliver Bethoux (2009). "The earliest beetle identified".  
  10. ^ William A. Shear & Patricia M. Bonamo (1990). "Fossil centipeds from the Devonian of New York State, U.S.A.". In Alessandro Minelli. Proceedings of the 7th International Congress of Myriapodology.  
  11. ^ Heather M. Wilson (2003). "A new scolopendromorph centipede (Myriapoda: Chilopoda) from the Lower Cretaceous (Aptian) of Brazil".  

Further reading

  • Stephen A. Schellenberg (2002). "Mazon Creek: preservation in late Paleozoic deltaic and marginal marine environments". In Walter Etter, James W. Hagadorn, Carol M. Tang & David J. Bottjer. Exceptional Fossil Preservation: A Unique View on the Evolution of Marine Life.  
  • Charles W. Shabica & Andrew A. Hay (ed.). Richardson's Guide to the Fossil Fauna of Mazon Creek.  
  • Jack Wittry (2006). The Mazon Creek Fossil Flora.  
  • Mike Sula (July 1, 2004). "The Vanishing Mother Lode of Mazon Creek".  

External links

  • Illinois State Museum Mazon Creek Fossil Exhibit
  • UC Berkeley Mazon Creek info
  • Northeastern Illinois University fossil fauna
  • Fossil News generalized diagram of Mazon Creek Delta and fossil photos
  • University of Bristol Mazon Creek flora and fauna discussed with photographed fossils
  • Mazon Creek Lagerstätte photo gallery

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