ABSTRACT

The study area includes approximately 825 sq. mi. in all or part of 31 townships in Haskell, Le Flore, McIntosh, and Muskogee Counties.

The Stigler coal is included in the McAlester Formation, Krebs Group, Desmoinesian Series, Pennsylvanian System. The study interval consists of the middle 2/3 of the McAlester Formation. The stratigraphic section is characterized by alternating, predominant shale and subordinate sandstones. The study interval thickens southeastward into the Arkoma Basin from less than 150 ft. in the northwest corner of the study area to nearly 500 ft. across southern Haskell and northwestern Le Flore Counties.

The shale units are primarily marine clay-shales and secondarily silty prodelta and carbonaceous marsh and swamp units. The sandstones vary from medium- to very fine-grained, moderate to well sorted, feldspar-and lithic-rich quartzarenites. Overall, general paleocurrent trend is east-southeastward. The sandstone facies are characterized by widely spaced lenticular channel sandstones with erosional bases and more widespread, thin bedded, interchannel sandstones with gradational contacts.

In general, that part of the McAlester Formation included in the study interval within the study area can be best described as a distal, mud-dominated, sequence of marine shale and sandstone, prodelta and interdistributary silty shales, and delta fringe and distributary sandstones, representing an eastward prograding lobe of a large deltaic complex to the west and northwest.

The presence of numerous thin coals and underclays, including the Stigler coal, in marine shales indicates periodic, abrupt sea level changes.

Three groups of the bituminous class are represented by the Stigler coal: (1) high volatile A bituminous, (2) medium volatile bituminous, and (3) low volatile bituminous. The Stigler coal is classified as a banded coal composed primarily of vitrain and secondarily of attritus. Thickness varies from 11 to 32 inches within the study area. Sulfur content is important economically and varies from less than 1 percent to over 5 percent. Ash content varies from 2.6 to 11.6 percent and closely parallels the distribution of sulfur.

Estimated recoverable reserves total over 50 million tons. Reserves are differentiated generally according to possible utilization based on sulfur content. Utilization is divided into two groups: (1) suitability for carbonization and (2) suitability for general fuel use.