Bed rock in the Rock Island area of northeastern Le Flore County in southeastern Oklahoma consists of shale, siltstone, and sandstone of the McAlester, Hartshorne, and Atoka Formations of Pennsylvanian age. The area is on the south flank of the Backbone anticline; the rocks dip to the south at 5o-45o. Alluvium along James Fork consists of sandy and clayey silt and may be as much as 30 feet thick.
Water in bedrock is under artesian conditions. The depth to water in most wells is less than 20 feet below the surface; a few wells flow. Yields of most wells probably are less than 5 gallons per minute. Water from nine wells was a sodium carbonate or sodium mixed anion type; dissolved-solids concentrations ranged from 294 to 1,250 milligrams per liter. No relationship between variations in chemistry of ground water and well depth, geographic distribution, or geologic formation is apparent.
James Fork has flow most of the time and discharge exceeds 25 cubic feet per second about one-half the time. The mean dissolved-solids concentration in James Fork water ranged from 224 milligrams per liter near Williams, Oklahoma, to 332 milligrams per liter near Hackett, Arkansas. Water in James Fork is a calcium magnesium sulfate type about 75 percent of the time. Maximum suspended sediment discharge was 2,720 tons per day. Silt-clay particles (diameters less than 0.062 millimeter) are the dominant sediment size.
Potential hydrologic effects of surface mining for coal include: (1) Creation of additional water storage in surface-mine ponds, (2) changes in rock permeability and ground-water storage, (3) changes in runoff and streamflow characteristics, (4) changes in drainage patterns, and (5) changes in the chemical quality and sediment load of James Fork. Although mining may increase the quantities of sediment and dissolved minerals added to James Fork, detection of these increases would be difficult because the potentially mineable area is very small in proportion to the total area of the basin.