Bigfork Chert

ARDMORE-SHERMAN- Limestone, gray, and dark-gray to black chert; thickness, 575 feet. Occurs in the OUACHITA MNTS. McALESTER TEXARKANA- Chert, dark-gray to black, with interbedded graptolitic black shales and fossiliferous gray to black cherty limestones; contains asphaltite seams; erodes into a mappable escarpment; thickness, 600 to 800 feet. (Same as Viola Limestone in Arbuckle Mountains.) Occurs in POTATO HILLS, BROKEN BOW UPLIFT or ADJACENT SMALLER UPLIFTS IN SOUTHEASTERN PART OF OUACHITA MOUNTAINS.
State Oklahoma
Name Bigfork Chert
Geologic age Middle Ordovician
Lithologic constituents
Major
Sedimentary > Carbonate > Limestone (Bed)
Sedimentary > Clastic > Mudstone > Shale (Bed)
Sedimentary > Chemical > Chert (Bed)
Comments Unit is found in many parts of Ouachita Range. Consists of close textured, even-bedded, brittle, dark-gray chert in layers 1 to 18 inches thick. Weathered parts look like sandstone. Is about 700 ft thick. Has been mapped as novaculite but it is not novaculite. (Purdue, 1909).
References

Heran, W.D., Green, G. and Stoeser, D.B., 2003, A Digital Geologic Map Database of Oklahoma: USGS Open File Report 03-247, scale 1:250,000.

https://pubs.er.usgs.gov/publication/ofr03247

Hart, D.L., 1974, Reconnaissance of the water resources of the Ardmore and Sherman quadrangles, southern Oklahoma: Oklahoma Geological Survey, Hydrologic Atlas 3, scale 1:250,000, 4 sheets. (Geology on sheet 1 compiled by D.L. Hart, and R.O. Fay, in 1970.)

Cederstrand, J.R., 1996a, Digital geologic map of Ardmore-Sherman quadrangles, south-central Oklahoma: U.S. Geological Survey Open-File Report 96-370, (3 diskettes), URL address is: http://ok.water.usgs.gov/gis/geology

https://pubs.er.usgs.gov/publication/ofr96370

Marcher, M.V. and Bergman, D.L., 1983, Reconnaissance of the water resources of the McAlester and Texarkana quadrangles, southeastern Oklahoma: Oklahoma Geological Survey, Hydrologic Atlas 9, scale 1:250,000, 4 sheets. (Geology on sheet 1 compiled by M.V. Marcher and D.L. Bergman, in 1971 and revised by R.O. Fay, in 1978.)

Cederstrand, J.R., 1996h, Digital geologic map of McAlester-Texarkana quadrangles, southeastern Oklahoma: U.S. Geological Survey Open-File Report 96-377, (3 diskettes), URL address is: http://ok.water.usgs.gov/gis/geology

https://pubs.er.usgs.gov/publication/ofr96377

Purdue, A.H., 1909, Structure and stratigraphy of the Ouachita Ordovician area, Arkansas: Geological Society of America Bulletin, pp.556-557.

NGMDB product
Counties Atoka - Latimer - McCurtain - Pushmataha