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
Coordinates 39°15′N 113°20′W / 39.25°N 113.33°W
Region House Range & Drum Range, Millard Co., west Utah
Country USA
Type section
Named for House Amphitheater (Geographic feature & type locality)
Named by Charles Doolittle Walcott

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]

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 turbidities and mudslides onto an oxygenated sea floor.[7] The productive layers comprise mud and clay particles, with a tiny fraction of wind-blown quartz.[9]

Stratigraphy

The Wheeler Shale spans the Ptychagnostus atavus[10] and uppermost-Middle Cambrian Bolaspidella trilobite zones (See House Range) for full stratigraphy).

Fauna

Incomplete list of the fauna of the Wheeler Shale:[6][11][12][13][14][15][16] (Note: the preservation of hard bodied trilobite remains and soft bodied animals seems to be mutually exclusive within particular horizons.)[4][17]


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 (11): 941–4, Bibcode:2003Geo....31..941G, doi:10.1130/G19926.1
  3. ↑ Robert R. Gaines; Derek E.G. Briggs ; Zhao Yuanlong (2008), "Cambrian Burgess Shale–type deposits share a common mode of fossilization", Geology 36 (10): 755–758, doi:10.1130/G24961A.1
  4. ↑ 4.0 4.1 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
  6. ↑ 6.0 6.1 6.2 Gunther, L.F.; Gunther, V.G. (1981), "Some Middle Cambrian Fossils of Utah", Brigham Young University Geology Studies 28: 1–81
  7. ↑ 7.0 7.1 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.
  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.
  9. ↑ Gaines, R. R.; Kennedy, M. J.; Droser, M. L. (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. doi:10.1016/j.palaeo.2004.07.034.
  10. ↑ 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.
  11. ↑ 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
  12. ↑ Photos of Wheeler Shale fossils from UC Berkeley
  13. ↑ 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, doi:10.2307/1303938
  14. ↑ Utah's Cambrian Life from University of Kansas Natural History Museum
  15. ↑ Cambrian fossils from Utah by the University of Utah
  16. ↑ Comprehensive treatment from The Virtual Fossil Museum
  17. ↑ 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