Trilobites of the Ninemile Shale

Ninemile Shale, Ibexian Series, Pseudocybele nasuta Zone (of western Utah), Whiterock Canyon Narrows (after Fortey and Droser, 1999). See also the Antelope Valley Limestone Formation.

Trilobites:

WHITEROCK CANYON:

Acidophorus? lineotuberculatus Fortey and Droser, 1999

Ampyxina (or Ampyxoides?) n. sp.

Benthamaspis sera Fortey and Droser, 1999

Carolinites sibiricus Chugaeva, 1964 (=? angustagena)

Cybelurus halo Fortey, 1980

Ectonotus whittingtoni Ross, 1967

Illaenus sp. B of Ross (1970)

Lachnostoma latucelsum Ross

Nileus hesperaffinis Ross, 1967

Nileus svalbardensis

Oopsites cf. O. hibernicus

Protopresbynileus n. sp.

Ptyocephalus spp. 

Raymondaspis vespertina Ross, 1967

COMMENTS:

The base of the Whiterockian (contact with Ibexian) is under some controversy and the trilobite faunas within the Antelope Valley Limestone and Ninemile Shale vary from place to place. At Whiterock Canyon, the "spike" at the base of the Whiterockian occurs at the boundary between the Ninemile and Antelope Valley Formations. At other localities (Rawhide, Meiklejohn Peak), the base of the Whiterockian doesn't necessarily coincide with formational boundaries. The trilobite faunas also vary due to different facies and correspondingly different trilobite biofacies. For more information, see Fortey and Droser ( 1999).

REFERENCES:

Fortey, R. A. and Droser, M. L. ( 1999)  Trilobites from the base of the type Whiterockian (Middle Ordovician) in Nevada. Journal of Paleontology, Vol. 73, No. 2, pp. 182-201

Loch, J. D. (2002)  Trilobite biostratigraphy across the base of the Whiterockian Series (Ordovician) for the proposed GSSP at Whiterock Canyon, Nevada. (web document)

Loch, J. D.  (2001)  New trilobite occurrences in the Whiterock Narrows section. (web document)