Wheeler Shale

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Wheeler Shale
Stratigraphic range:
Middle Cambrian
~507 Ma
File:ElrathiakingiUtahWheelerCambrian.jpg
Elrathia kingii, famed trilobite of the Wheeler Shale.
TypeGeological formation
Thickness100–200 m (330–660 ft)
Lithology
PrimaryCalcareous shale
OtherMudstone, shaley limestone and limestone
Location
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RegionHouse Range and Drum Mountains, Millard Co., west Utah
CountryUnited States
Type section
Named forHouse Amphitheater (Geographic feature and type locality)
Named byCharles 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-Lagerstätte. 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 (1,610 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 Mountains, northwest of the House Range where similar fossils and preservation are found.[6]

Taphonomy and sedimentology

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File:Asaphiscuswheelerii.jpg
Asaphiscus wheeleri, Cambrian, Wheeler shale, Utah
File:Emeraldella brocki.jpg
Emeraldella brocki an arthropod From the Burgess Shale

Detailed work recognises a number of ~10 m thick lagerstätten sequences in the formation, each of which formed at a sea-level highstand[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

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

Fauna

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File:Stanleycaris sp. KUMIP 153923.png
Stanleycaris sp. from Wheeler shale, originally described as Aysheaia prolata

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

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Arthropoda

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Dinocaridida

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Trilobita

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Brachiopoda

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Chordata

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Cnidaria

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Mollusca

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Echinodermata

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Porifera

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Priapulida

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Unclassified

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References

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  12. ^ Photos of Wheeler Shale fossils from UC Berkeley
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  14. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  15. ^ Cambrian fossils from Utah by the University of Utah[permanent dead link]
  16. ^ Comprehensive treatment from The Virtual Fossil Museum
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