Bigfork Chert

The Bigfork Chert is a Middle to Late Ordovician geologic formation in the Ouachita Mountains of Arkansas and Oklahoma. First described in 1892,[4] this unit was not named until 1909 by Albert Homer Purdue in his study of the Ouachita Mountains of Arkansas.[3] Purdue assigned the town of Big Fork in Montgomery County, Arkansas as the type locality, but did not designate a stratotype. As of 2017, a reference section for this unit has yet to be designated. The Bigfork Chert is known to produce planerite, turquoise, variscite, and wavellite minerals.[5]

Bigfork Chert
Stratigraphic range: Ordovician
TypeFormation
Unit ofnone
Sub-unitsnone
UnderliesPolk Creek Shale[1]
OverliesWomble Shale
Thickness450 to 750 feet[2]
Lithology
PrimaryChert
Location
RegionArkansas, Oklahoma
CountryUnited States
Type section
Named forBig Fork, Montgomery County, Arkansas
Named byAlbert Homer Purdue[3]

Paleofauna

Graptolites
C. antiquus[6]
  • Dicellograptus
D. divaricatus[6]
D. trifidus[6]
D. vulgatus[6]
  • Glyptograptus[6]
  • Lasiograptus
L. flaccidus[6]
  • Mesograptus
M. perexcavatus[6]
  • Orthograptus
O. quadrimucronatus[6]

See also

References
  1. Harlton, B.H. (1953). "Ouachita chert facies, southeastern Oklahoma". AAPG Bulletin. 37 (4): 778–796. ISSN 0149-1423. Wikidata Q63311479.
  2. McFarland, John David (2004) [1998]. "Stratigraphic summary of Arkansas" (PDF). Arkansas Geological Commission Information Circular. 36: 19. Archived from the original (PDF) on 2016-12-21. Retrieved 2018-01-09.
  3. Purdue, A.H. (1909). Slates of Arkansas. Geological Survey of Arkansas. pp. 30, 35.
  4. Griswold, L.S. (1892). "Whetstones and the novaculites". Annual Report of the Geological Survey of Arkansas for 1890. 3.
  5. Barwood, Henry (1997). "Occurrence of turquoise group minerals in the eastern United States". The Mineralogical Record. 28 (1): 53.
  6. Miser, H.D.; Purdue, A.H. (1929). "Geology of the De Queen and Caddo Gap quadrangles, Arkansas" (PDF). U.S. Geological Survey Bulletin. 808. doi:10.3133/B808. ISSN 8755-531X. Wikidata Q60894700.


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