Bigfork Chert

Bigfork Chert
Stratigraphic range: Ordovician
Type Formation
Unit of none
Sub-units none
Underlies Polk Creek Shale
Overlies Womble Shale
Thickness 450 to 750 feet[1]
Lithology
Primary Chert
Location
Region Arkansas, Oklahoma
Country United States
Type section
Named for Big Fork, Montgomery County, Arkansas
Named by Albert Homer Purdue[2]

The Bigfork Chert is a Middle to Late Ordovician geologic formation in the Ouachita Mountains of Arkansas and Oklahoma. First described in 1892,[3] this unit was not named until 1909 by Albert Homer Purdue in his study of the Ouachita Mountains of Arkansas.[2] 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.[4]

Paleofauna

Graptolites

C. antiquus[5]
  • Dicellograptus
D. divaricatus[5]
D. trifidus[5]
D. vulgatus[5]
  • Glyptograptus[5]
  • Lasiograptus
L. flaccidus[5]
  • Mesograptus
M. perexcavatus[5]
  • Orthograptus
O. quadrimucronatus[5]

See also

References

  1. ↑ McFarland, John David (2004) [1998]. "Stratigraphic summary of Arkansas" (PDF). Arkansas Geological Commission Information Circular. 36: 19.
  2. 1 2 Purdue, A.H. (1909). Slates of Arkansas. Geological Survey of Arkansas. pp. 30, 35.
  3. ↑ Griswold, L.S. (1892). "Whetstones and the novaculites". Annual Report of the Geological Survey of Arkansas for 1890. 3.
  4. ↑ Barwood, Henry (1997). "Occurrence of turquoise group minerals in the eastern United States". The Mineralogical Record. 28 (1): 53.
  5. 1 2 3 4 5 6 7 8 9 Miser, Hugh D.; Purdue, A.H. (1929). "Geology of the De Queen and Caddo Gap quadrangles, Arkansas". U.S. Geological Survey Bulletin. 808: 38–39.


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