| Bigfork Chert | |
|---|---|
| Stratigraphic range: Ordovician | |
| Type | Formation |
| Unit of | none |
| Sub-units | none |
| Underlies | Polk Creek Shale [1] |
| Overlies | Womble Shale |
| Thickness | 450 to 750 feet [2] |
| Lithology | |
| Primary | Chert |
| Location | |
| Region | Arkansas, Oklahoma |
| Country | United States |
| Type section | |
| Named for | Big Fork, Montgomery County, Arkansas |
| Named by | Albert Homer Purdue [3] |
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]
Paleofauna
Graptolites
- C. antiquus [6]
- D. divaricatus [6]
- L. flaccidus [6]
- M. perexcavatus [6]
- O. quadrimucronatus [6]
See also
References
- ^ Harlton, B.H. (1953). "Ouachita chert facies, southeastern Oklahoma". AAPG Bulletin. 37 (4): 778–796. ISSN 0149-1423. Wikidata Q63311479.
- ^ 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.
- ^ a b Purdue, A.H. (1909). Slates of Arkansas. Geological Survey of Arkansas. pp. 30, 35.
- ^ Griswold, L.S. (1892). "Whetstones and the novaculites". Annual Report of the Geological Survey of Arkansas for 1890. 3.
- ^ Barwood, Henry (1997). "Occurrence of turquoise group minerals in the eastern United States". The Mineralogical Record. 28 (1): 53.
- ^ a b c d e f g h i 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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