Wheeler Shale

Wheeler Shale
Stratigraphic range: Middle Cambrian (c. 507 Ma)

Elrathia kingii, famed trilobite of the Wheeler Shale.
Type Geological formation
Thickness 100-200 metres
Lithology
Primary Calcareous Shale
Other Mudstone, Shaley Limestone & Limestone
Location
Named for House Amphitheater (Geographic feature & type locality)
Named by Charles Doolittle Walcott
Region House Range & Drum Range, Millard Co., west Utah
Country USA

The Wheeler Shale (named by Charles Walcott) is a Cambrian (c. 507 Ma) fossil locality world famous[1] for prolific agnostid and Elrathia kingii trilobite remains (even though many areas are barren of fossils)[2] and represents a Konzentrat-Lagerstätten. Varied soft bodied organisms are locally preserved, a fauna (including Naraoia, Wiwaxia and Hallucigenia) and preservation style (carbonaceous film) normally associated with the more famous Burgess Shale.[3] As such, the Wheeler Shale also represents a Konservat-Lagerstätten.[4]

Together with the Marjum Formation and lower Weeks Formation, the Wheeler Shale forms 490 to 610 m (1,600 to 2,000 ft) of limestone and shale exposed in one of the thickest, most fossiliferous and best exposed sequences of Middle Cambrian rocks in North America.[5]

At the type locality of Wheeler Amphitheater, House Range, Millard County, western Utah, the Wheeler Shale consists of a heterogeneous succession of highly calcareous shale, shaley limestone, mudstone and thin, flaggy limestone.[6] The Wheeler Formation (although the Marjum & Weeks Formations are missing) extends into the Drum Range, northwest of the House Range where similar fossils and preservation are found.[6]

Contents

Taphonomy & Sedimentology

Further information: Burgess Shale type preservation

Detailed work recognises a number of ~10 m thick lagerstätten sequences in the formation, each of which formed at a sea-level high stand[7] in deep water.[8] The lagerstätte were deposited by turbitides and mudslides onto an oxygenated sea floor.[7]

Stratigraphy

The Wheeler Shale spans the Ptychagnostus atavus[9] and uppermost-Middle Cambrian Bolaspidella trilobite zones (See House Range) for full stratigraphy).

Fauna

Main article: Burgess Shale type fauna

Incomplete list of the fauna of the Wheeler Shale:[6][10][11][12][13][14][15] (Note: the preservation of hard bodied trilobite remains and soft bodied animals seems to be mutually exclusive within particular horizons.)[4][16]

Protista

Arthropoda

Arachnomorpha

Trilobita

Brachiopoda

Chordata

Cnidaria

Mollusca

Echinodermata

Porifera

Priapulida

Unclassified

Gallery

References

  1. ^ Johnson, Kirk; Troll, Ray (2007), Cruising the fossil freeway: An epoch tale of a scientist and an artist on the ultimate 5,000-Mile paleo road trip, Golden, CO.: Fulcrum Publishing, ISBN 978-1-55591-451-6 
  2. ^ Robert R. Gaines; Mary L. Droser (2003), "Paleoecology of the familiar trilobite Elrathia kingii: An early exaerobic zone inhabitant" (pdf), Geology 31: 941–4, doi:10.1130/G19926.1, http://earthsciences.ucr.edu/docs/Gaines&Droser_2003.pdf 
  3. ^ Robert R. Gaines; Derek E.G. Briggs ; Zhao Yuanlong (2008), "Cambrian Burgess Shale–type deposits share a common mode of fossilization", Geology 36: 755–758, doi:10.1130/G24961A.1 
  4. ^ a b Gaines, R; Kennedy, M; Droser, M (2005), "A New Hypothesis for Organic Preservation of Burgess Shale Taxa in the Middle Cambrian Wheeler Formation, House Range, Utah", Palaeogeography Palaeoclimatology Palaeoecology 220: 193–205, doi:10.1016/j.palaeo.2004.07.034 
  5. ^ Robison, R.A. (1964), "Late Middle Cambrian faunas from western Utah", Journal of Paleontology 38 (3): 510–566, http://jpaleontol.geoscienceworld.org/cgi/content/abstract/38/3/510 
  6. ^ a b c Gunther, L.F.; Gunther, V.G. (1981), "Some Middle Cambrian Fossils of Utah", Brigham Young University Geology Studies 28: 1–81 
  7. ^ a b Brett, C. E.; Allison, P. A.; Desantis, M. K.; Liddell, W. D.; Kramer, A. (2009). "Sequence stratigraphy, cyclic facies, and lagerstätten in the Middle Cambrian Wheeler and Marjum Formations, Great Basin, Utah". Palaeogeography Palaeoclimatology Palaeoecology 277: 9–33. doi:10.1016/j.palaeo.2009.02.010.  edit
  8. ^ Halgedahl, S. L.; Jarrard, R. D.; Brett, C. E.; Allison, P. A. (2009). "Geophysical and geological signatures of relative sea level change in the upper Wheeler Formation, Drum Mountains, West-Central Utah: A perspective into exceptional preservation of fossils". Palaeogeography Palaeoclimatology Palaeoecology 277 (1–2): 34–56. doi:10.1016/j.palaeo.2009.02.011.  edit
  9. ^ Lieberman, B. S. (2003). "A New Soft-Bodied Fauna: the Pioche Formation of Nevada". Journal of Paleontology 77 (4): 674–690. doi:10.1666/0022-3360(2003)077<0674:ANSFTP>2.0.CO;2. ISSN 0022-3360.  edit
  10. ^ Briggs, D.E.G.; Robison, R.A. (1984), Exceptionally preserved nontrilobite arthropods and Anomalocaris from the Middle Cambrian of Utah, The Paleontological Institute, The University of Kansas, http://kuscholarworks.ku.edu/dspace/handle/1808/3656 
  11. ^ Photos of Wheeler Shale fossils from UC Berkeley
  12. ^ Rigby, J.K. (1978), "Porifera of the Middle Cambrian Wheeler Shale, from the Wheeler Amphitheater, House Range, in western Utah.", Journal of Paleontology 52 (6): 1325–1345 
  13. ^ Utah's Cambrian Life from University of Kansas Natural History Museum
  14. ^ Cambrian fossils from Utah by the University of Utah
  15. ^ Comprehensive treatment from The Virtual Fossil Museum
  16. ^ Gaines, Robert R.; Droser, Mary L.; Kennedy, Martin J. (2001), "Taphonomy of soft-bodied preservation and ptychopariid Lagerstätte in the Wheeler Shale (Middle Cambrian), House Range, USA; controls and implications.", PaleoBios 21 (Suppl.2): 1–55, http://www.ucmp.berkeley.edu/napc/abs9.html 
Localities
Burgess shale, Chengjiang, Sirius Passet, Emu Bay, Kinzers formation, Wheeler Formation, Pioche Shale
Modes of preservation in the Cambrian
Exceptional
Phosphate
Carbonaceous film
Casts and moulds

Legged trilobite fossil
Conventional
Shelly
Small shelly fossils · Conventional fossils
Organic
Acritarchs · Organic-walled microfossils
Traces
Microbialites · Trace fossils