Specimen Ridge

Coordinates: 44°52′13″N 110°17′48″W / 44.87028°N 110.29667°W / 44.87028; -110.29667 (Specimen Ridge)
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Specimen Ridge
North face Specimen Ridge from Lamar Valley
Highest point
Elevation8,379 ft (2,554 m)[1]
Coordinates44°52′13″N 110°17′48″W / 44.87028°N 110.29667°W / 44.87028; -110.29667 (Specimen Ridge)[1]
Geography
LocationYellowstone National Park, Park County, Wyoming, U.S.
Parent rangeWashburn Range
Topo mapAmethyst Mountain

Specimen Ridge, el. 8,379 feet (2,554 m) is an approximately 8.5-mile (13.7 km) ridge along the south rim of the Lamar Valley in Yellowstone National Park. The ridge separates the Lamar Valley from Mirror Plateau. The ridge is oriented northwest to southeast from the Tower Junction area to Amethyst Mountain. The ridge is known for its abundance of amethyst, opal and petrified wood. It was referred to as Specimen Mountain by local miners and was probably named by prospectors well before 1870.[2] The south side of the ridge is traversed by the 18.8-mile (30.3 km) Specimen Ridge Trail between Tower Junction and Soda Butte Creek. The trail passes through the Petrified Forest[3] and over the summit of Amethyst Mountain el. 9,614 feet (2,930 m).[4]

Geology

Specimen Ridge consists of a geological

lahars) that are complexly interlayered with braided and meandering stream deposits. The lahar (mudflow) deposits consist of normally massive and structureless, matrix-supported conglomerates that contain subangular, poorly sorted gravel that range in size from 1 cm (0.39 in) to 2 meters (6.6 ft) in diameter. The majority of the sediments consist of well-bedded, clast-supported fluvial conglomerates that consist of grain-supported, subrounded, and moderately well-sorted gravel that typically ranges in size from 1 cm (0.39 in) to 30 cm (12 in). The vast majority of petrified wood occurs within the conglomerates. The fossil leaves, needles, pollen, and cones are largely found within tuffaceous sandstones and siltstones that were deposited either along the banks of either braided or meandering rivers, within their abandoned channels, or in shallow lakes of very limited extent. At Specimen Ridge, these sediments consist of volcanic material eroded from and accumulated downslope of an adjacent Eocene stratovolcano, known the 'Washburn Volcano', in an intermountaine basin. The Lamar River Formation is part of the Washburn Group.[5][6][7][8][9]

The Lamar River Formation is part of the Absaroka Volcanic Supergroup. It is a thick accumulation of volcanic rocks that were either erupted from or eroded from the slopes of two belts of Eocene stratovolcanoes. These rocks accumulated within an intermountain basin between these belts. Before they were destroyed by erosion, these volcanoes are estimated to have had peaks that rose about 8,000 feet (2,400 m) to 10,000 feet (3,000 m) above adjacent intermountain valleys. Depending on location, the Lamar River Formation

Mississippian limestones and dolomites; or Precambrian gneiss. Based on radiometric dates and plant fossils from it, the Lamar River Formation is considered to be of Middle Eocene age.[5][10]

Yellowstone Petrified Forest

Within the Specimen Ridge, exposures of the Lamar River Formation is well known for the

petrified forests and petrified wood concentrations. The concentrations of silicified wood, upright standing, petrified tree trunks, and associated buried petrified forests of Specimen Ridge and adjacent Amethyst Mountain are collectively known as Yellowstone Petrified Forest. They have been known to science and studied for over 130 years.[11][12][13][14][15]

Within Specimen Ridge, the Yellowstone Petrified Forest consists of a mixture of fossilized, in place (

In regard to these fossil forests and other fossils, collecting of fossils in Yellowstone National Park is illegal. In addition, visitors should stay on marked and maintained trails.[13]

See also

  • Erling Dorf
  • Mountains and mountain ranges of Yellowstone National Park

References

  1. ^ a b "Specimen Ridge". Geographic Names Information System. United States Geological Survey, United States Department of the Interior. Retrieved 2009-12-31.
  2. ^ Knowlton, F. H. (1914) The Fossil Forests of Yellowstone National Park. National Park Service, Department of the Interior, Office of the Secretary, Wasignton DC. 31 pp. Last accessed September 23, 2013.
  3. (pp. 199–202)
  4. ^ a b c Fritz, WJ (1980a) Depositional Environment of the Eocene Lamar River Formation in Yellowstone National Park. Doctoral Dissertation, The University of Montana, Missoula, Montana.
  5. ^ Fritz, WJ (1980b) Stratigraphic framework of the Lamar River formation in Yellowstone National Park. Northwest Geology. vol. 9, pp. 1-18.,
  6. ^ a b Fritz, WJ (1981) Reinterpretation of the depositional environment of the Yellowstone fossil forests: Reply. Geology. 9(2):53-54.
  7. ^ a b Fritz, WJ (1982) Geology of the Lamar River Formation, northeast Yellowstone National Park. In SG Reid and DJ Foote, eds., pp. 73-101, Geology of Yellowstone Park Area. Wyoming Geological Association Guidebook, 33rd Annual Field Conference, 1982, Wyoming Geological Association, Casper, Wyoming.
  8. ^ Feeley, TC, MA Cosca, MA and CR Lindsay (2002) Petrogenesis and implications of calc-alkaline cryptic hybrid magmas from Washburn Volcano, Absaroka Volcanic Province, USA. Journal of Petrology. 43(4):663-703.
  9. ^ Smedes, HW, and HJ Prostka, 1972, Stratigraphic framework of the Absaroka Volcanic Supergroup in the Yellowstone National Park region. Professional Paper no. 729-C, U. S. Geological Survey, Reston, Virginia. 33 pp.
  10. ^ Holmes, WH (1879) Fossil forests of the volcanic Tertiary formation of Yellowstone National Park. Geological and Geographical Survey of the Territories. Bulletin of the Survey vol. 5, no. 1, pp. 125-132. United States Geological and Geographical Survey, Department of the Interior, Washington DC
  11. ^ Knowlton, FH (1914) The Fossil Forests of Yellowstone National Park. National Park Service, Department of the Interior, Office of the Secretary, Washington DC. 31 pp. Last accessed September 26, 2013.
  12. ^ a b Dorf, E (1960) Tertiary fossil forests of Yellowstone National Park, Wyoming. in DE Campau, HW Anisgard, and RL Egbet, pp. 253-260, Guidebook, 11th Annual Field Conference, Billings Geological Society, Casper, Wyoming.
  13. ^ Dorf, E (1964) The 'petrified forests' of Yellowstone Park. Scientific American. 210(4):106-114.
  14. ^ Dorf, E (1980) Petrified Forests of Yellowstone. National Park Service, U.S. Department of Interior, Washington, D.C., 31 pp.
  15. ^ a b c Karowe, AL. and TH Jefferson (1987) Burial of trees by eruptions of Mount St. Helens, Washington; implications for the interpretation of fossil forests. Geological Magazine. 124(3):191-204.
  16. ^ Fritz, WJ (1983) Comment on 'Erect floating stumps in Spirit Lake, Washington' Geology 11(12):733-734
  17. ^ Fritz, WJ, (1980c) Reinterpretation of the depositional environment of the Yellowstone "fossil forests". Geology. 8:(7):309-313.
  18. ^ Fritz, WJ, and S Harrison (1985) Transported trees from the 1982 Mount St. Helens sediment flows--Their use as paleocurrent indicators. Sedimentary Geology 42(1-2):49-64.
  19. ^ Cameron, KA, and PT Pringle (1991) Prehistoric buried forests of Mount Hood. Oregon geology. 53(2):34-43.

External links