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National Geologic Map Database
Geologic Unit: Ouachita
Map showing publication footprint
  • Usage in publication:
    • Ouachita shale
  • Modifications:
    • Original reference
  • Dominant lithology:
    • Shale
    • Limestone
  • AAPG geologic province:
    • Ouachita folded belt
Publication:

Purdue, A.H., 1909, The slates of Arkansas: Arkansas Geological Survey, p. 1-95, (incl. geologic map)


Summary:

Pg. 30, 33. Ouachita shale. Chiefly dark-colored clay shale, but not uncommonly the dark layers alternate with green ones. In many places slaty cleavage is developed, when the alternating dark and green layers produce ribboned slate. Thin layers of limestone are interbedded in lower part. Quartz veins and thin layers of hard flinty material are common. Thickness probably not less than 900 feet. Grades into underlying Crystal Mountain sandstone [which at this time included Blakely sandstone, according to H.D. Miser, 1917]. Unconformably overlain by 75 to 150 feet of shale called Stringtown shale [only a part of typical Stringtown shale], which separates it from overlying Bigfork chert. [Age is Early and Middle Ordovician.]
[Named from Ouachita Mountains, southwestern AR, the pronunciation of which is Washita.]

Source: US geologic names lexicon (USGS Bull. 896, p. 1577).


Map showing publication footprint
  • Usage in publication:
    • Ouachita shale*†
  • Modifications:
    • Abandoned
  • AAPG geologic province:
    • Ouachita folded belt
Publication:

Miser, H.D., 1918, Manganese deposits of the Caddo Gap and De Queen quadrangles, Arkansas, IN Contributions to economic geology (short papers and preliminary reports), 1917; Part 1, Metals and nonmetals except fuels: U.S. Geological Survey Bulletin, 660-C, p. C59-C122.


Summary:

Interpreted †Ouachita shale as = Mazarn shale, Blakely sandstone, and lower part of Womble shale of present terminology. (See 1917 entry under Blakely sandstone.)

Source: US geologic names lexicon (USGS Bull. 896, p. 1577).


For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.

Asterisk (*) indicates usage by the U.S. Geological Survey. Other usages by state geological surveys.

"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).

Slash (/) indicates name does not conform with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005). This may be explained within brackets ([ ]).