Trilobite Point
| Trilobite Point | |
|---|---|
 Trilobite Point (right of Mount Holmes) from Madison River | |
| Highest point | |
| Elevation | 10,010 ft (3,050 m) |
| Coordinates | 44°49′01″N 110°50′38″W / 44.81694°N 110.84389°W[1] |
| Geography | |
 | |
| Location | Yellowstone National Park, Park County, Montana |
| Parent range | Gallatin Range |
Trilobite Point is a mountain peak in the southern section of the Gallatin Range in Yellowstone National Park. It has an elevation of 10,010 feet (3,050 m). In 1883, William Henry Holmes of the Hayden expedition named it after trilobite-bearing exposures of Cambrian sedimentary strata that he found just below its summit and around it.[2]
Geology
[edit]The summit of Trilobite Point consists of an erosional outlier of the unfossiliferous cherty dolomites of the Ordovician Bighorn Dolomite. Underlying the Bighorn Dolomite and exposed in steep slopes, from youngest to oldest, are the Cambrian limestones, dolomites, shales, and sandstones of the Snowy Range Formation, Pilgrim Limestone, Park Shale, Meagher Formation, Wolsey Shale, and Flathead Sandstone. The Flathead Sandstone is underlain by Precambrian metamorphic rocks. These strata are intruded by two, thin rhyodacite porphyry sills. A third, thicker rhyodacite porphyry sill separates the Flathead Sandstone from the underlying gneissic metamorphic rocks.[3]
Fossils
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The most fossiliferous of these geologic formations is the Pilgrim Limestone. Abundant trilobite] fragments have been observed, often as a fossil hash, as discrete beds in its lower and middle parts. Within Yellowstone National Park, the Pilgrim Limestone has yielded fossils of the enigmatic Chancelloria, hyoliths, brachiopods, trilobites, and conodonts. One of Walcott’s[4] trilobites, Solenopleura? weedi, is now attributed to the Pilgrim Limestone. Cambrian sponge spicules, hyoliths, brachiopods, trilobites, crinoid fragment, and invertebrate trace fossils have been collected from 11 outcrops within the vicinity of Trilobite Point.[5][6]
Hebgen Lake earthquake of August 17, 1959
[edit]During Hebgen Lake earthquake of August 17, 1959, the fire lookout on Mount Holmes reported that a crack opened across the ridge between Mount Holmes and Trilobite Point. It was not determined whether it was a either a small fault scarp caused by vertical displacement along a bedrock fault or the result of slumping in unconsolidated regolith.[7]
See also
[edit]Notes
[edit]- ^ "Trilobite Point". Geographic Names Information System. United States Geological Survey, United States Department of the Interior.
- ^ Holmes, W.H., 1883. On the Geology of Yellowstone National Park. in Hayden, F.V., ed., pp. 1-62. Twelfth Annual Report of the United States Geological and Geographical Survey of the Territories: A report of progress of the exploration in Wyoming and Idaho for the year 1878. Part II: Yellowstone National Park. Geology—Thermal Springs—Topography. Washington, D.C., U.S. Geological and Geographical Survey of the Territories and Government Printing Office, 681 pp.
- ^ Ruppel, E.T., 1972. Geology of pre-Tertiary rocks in the northern part of Yellowstone National Park, Wyoming. U.S. Geological Survey Professional Paper, 729. 66 pp.
- ^ Walcott, C.D., 1899, Chapter XII. Section 1.- Cambrian Fossils. in Hague, A., ed., pp. 440-479. Geology of the Yellowstone National Park: Part II. Descriptive geology, petrography, and paleontology. U.S. Geological Survey Monograph, 32, Part 2. Monograph 32, 893 pp.
- ^ Tweet, J.S., Santucci, V.L., and Connors, T., 2013. Paleontological resource inventory and monitoring: Greater Yellowstone Network. Natural Resource Report, NPS/GRYN/NRTR—2013/794. Fort Collins, Colorado, National Park Service. 418 pp.
- ^ Norr, M.R., V.L. Santucci, and J.S. Tweet., 2016. An inventory of trilobites from National Park Service areas. in Sullivan, R.M., and Lucas, S.G., eds. Fossil Record 5. New Mexico Museum of Natural History and Science Bulletin, 74, pp. 179-203.
- ^ Myers, W.B., and Hamilton, W., 1964. Deformation accompanying the Hebgen Lake earthquake of August 17, 1959. in Anonmynous, ed., pp. 55-98. The Hebgen Lake, Montana, earthquake of August 17, 1959. U.S. Geological Survey Professional Paper, 435, 242 pp.
Yellowstone National Park - Mammoth Hot Springs | ||
|---|---|---|
Historic structures and other attractions in the Mammoth Hot Springs area | ||
| Structures and history |  | |
| Geography and geology | ||
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