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The Coal Hill, Hartman, and Clarksville quadrangles enclose an area of approx. 182 sq miles in Johnson, Logan, and Franklin counties in NW. Arkansas. Sedimentary rocks penetrated by wells drilled for gas in the area range in age from Middle Ordovician to Middle Pennsylvanian. Rocks of the Atoka and Des Moines Series of Pennsylvanian age and terrace deposits and alluvium of Pleistocene and Recent age crop out in the area. The exposed rocks consist mainly of dark-gray shale, light- to medium-gray siltstone and sandstone, and a few beds of coal. The sedimentary rocks are folded into gently dipping generally E.-W.-trending anticlines and synclines and are broken by normal faults striking generally east-west. The structural relief, measured on the base of the Hartshorne Sandstone, is about 1,600 ft. Natural gas, coal, building stone, road metal, gravel, sand, and clay are of commercial importance in the area. The reported potential production of gas is about 331 Mcfd. The Lower Hartshorne coal bed in the McAlester Formation has approx. 348 million short tons of remaining reserves. (20 refs.)

Geology of the Coal Hill, Hartman, and Clarksville quadrangles, Johnson County and vicinity, Arkansas