Trilobites are rare in Colorado and occur mainly in the Manitou Formation.
Manitou Formation (L. Ord.):
Trilobites:
Bellefontia cf. B. chamberlaini Clark
Hystricurus? aff. H.? genacurus (Hintze)
Kainella sp. cf. K. billingsi Walcott
Leiostegium (Leoistegium) manitouensis Walcott, 1925
Leiostegium (Manitouella) ulrici
Symphysurina cf. S. globocapitella Hintze
other fossils: cystoids, trace fossils, brachiopods, stromatolites, possible hyolithid (?Kainella spine?)
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Peerless Formation (U. Cam.):
Trilobites:
Ellipsocephaloides butler Resser
Idahoia wisconsensis (Owen)
Idahoia sp.
Ptychaspis granulusa (Owen)
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REFERENCES:
Bass, N.W. and Northrop, S.A., 1953, Dotsero and Manitou formations, White River Plateau, Colorado, with special reference to Clinetop algal limestone member of Dotsero formation: American Association of Petroleum Geologists Bulletin, v. 37, no. 5, p. 889-912
Bassett, C.F., 1939, Paleozoic section in the vicinity of Dotsero, Colorado: Geological Society of America Bulletin, v. 50, no. 12, pt. 1, p. 1851-1866
Berg, Robert R. and Ross, Reuben Jr. (1959) Trilobites from the Peerless and Manitou Formations of Colorado, Journal of Paleontology, v.33, No.1, p. 106-119, January 1959.
Brainerd, E.A., Baldwin, H.L., Jr., and Keyte I.A., 1933, Pre-Pennsylvanian Stratigraphy of Front Range in Colorado; Bull. Am. Ass. Petroleum Geologists, v. 17, p. 375-396
Gerhard, L.C., 1972, Canadian depositional environments and paleotectonics, central Colorado, IN De Voto, R.H., ed., Paleozoic stratigraphy and structural evolution of Colorado: Colorado School of Mines Quarterly, v. 67, no. 4, p. 1-36
Myrow, Paul M., John F. Taylor, James F. Miller, Raymond L. Ethington, Robert L. Ripperdan, and Joseph Allen (2002) Fallen arches: Dispelling myths concerning Cambrian and Ordovician paleogeography of the Rocky Mountain region. Geological Society of America Bulletin: Vol. 115, No. 6, pp. 695–713.
COMMENTS:
The main trilobite-bearing formation in Colorado is the Manitou Formation (Manitou Dolomite), which is Lower Ordovician in age. The Manitou Formation is composed of mainly limestone, dolomite, and red dolomite. It has been divided into the Deadhorse and Tie Gulch Members in its northwest province near Glenwood Springs, Garfield Co. in the Piceance basin and the Helena Canyon, Ptarmigan, and Fairplay Members in its southeast province near Salida, Gunnison Co. in the Piceance basin. The Manitou Formation is exposed along the Front Range of Colorado, and extends southward (as far as the San Luis Valley), and north and west (as far as the northern Sangre De Cristo range in the San Isabel National Forest of south central Colorado).
The Manitou Formation is underlain by the Dotsero Formation (Dotsero Dolomite) or the Peerless Formation, both of which are Upper Cambrian and consist of carbonates, dolomitic sandstones and dolomitic shales. The Dotsero Formation is divided into a lower Glenwood Canyon Member and is capped by the Clinetop algal limestone Member (Stromatolite Bed). Below these formations is the early Late Cambrian Sawatch Formation (also called the Sawatch Quartzite or Sawatch Sandstone). All formations mentioned above comprise the Horseshoe Mountain Group which is named for exposures on Horseshoe Mountain in Park County. Rocks of the group include conglomerate, sandstone, shale, limestone, and dolomite. The thickness of the group in the southeast facies is 352 ft: Manitou, 167 ft; Peerless, 35 ft; and Sawatch, 150 ft. The thickness of the group in the northwest facies is 772 ft: Manitou, 156 ft; Dotsero, 96 ft; and Sawatch, 520 ft. The Manitou Formation is overlain by the Harding Formation.
OTHER trilobite-bearing formations in Colorado:
We do not as yet have much information on these formations.
Minturn Formation (Pennsylvanian) has produced several trilobite fragments.
Trilobites:
Phillipsidae
Ameura sangamonensis (Meek & Worthen)
References:
Roth, R., and J. Skinner, 1930. The fauna of the McCoy Formation, Pennsylvanian, of Colorado. Journal of Paleontology, 4:332-352.
Stevens, C.H., 1958. Stratigraphy and Paleontology of the McCoy, Colorado Area. Unpublished M.A.thesis, University of Colorado, Boulder, 242 p.
Fossils of McCoy, Colorado, by Wayne M. Itano
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Glen Eerie Formation (Mostly Lower Pennsylvanian, but perhaps slightly
upper Mississippian) has produced trilobite fragments.
Trilobites:
Phillipsidae
Ameura sangamonensis (Meek & Worthen)
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Williams Canyon carbonates (Williams Canyon Formation) is an
Upper Devonian and Lower Mississippian deposit which may contain trilobites.
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Chaffee Fm., Dyer Dolomite Member, Devonian
-brachiopods found in this formation - should be trilobites.
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Beldon Fm., Pennsylvanian
Trilobites:
Ditomopyge parvulus (Girty)
Reference:
Ridlon, James Barr (1954) Stratigraphy and paleontology of the Belden Formation in part of West Central Colorado, Masters Thesis, University of Colorado, Boulder, 1954
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Ouray Limestone, Mississippian:
Trilobites:
Phillipsia peroccidens Hall and Whitfield
Reference:
Girty, George H. (1903) The Carboniferous Formations and Faunas of Colorado, USGS Prof. Paper 16.
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Hermosa Formation, Pennsylvanian:
Trilobites:
Phillipsia major Shumard
Phillipsia trinucleata Herrick (?= Sevillia trinucleata)
Reference:
Girty, George H. (1903) The Carboniferous Formations and Faunas of Colorado, USGS Prof. Paper 16.
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Weber Formation, Pennsylvanian:
Trilobites:
Phillipsia major Shumard
Reference:
Girty, George H. (1903) The Carboniferous Formations and Faunas of Colorado, USGS Prof. Paper 16.
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Maroon Formation, Pennsylvanian:
Trilobites:
Phillipsia trinucleata Herrick (?= Sevillia trinucleata)
Reference:
Girty, George H. (1903) The Carboniferous Formations and Faunas of Colorado, USGS Prof. Paper 16.
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Acknowledgements:
Thanks to Jerry Suchan and Wayne Itano for assistance on this page.
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