AGS / Energy / Coal / Geology
The Arkansas coalfields are made up of a series of coal basin districts that underlie parts of an area about 33 miles wide and 60 miles long in parts of Crawford, Franklin, Johnson, Logan, Pope, Sebastian, and Scott Counties (Figure 1). Coal has been mined commercially in two districts of west-central Arkansas (Table 1). Of the 19 or 20 coalbeds in the Arkansas Valley investigated in the past by state and federal agencies, only four have been considered to be of economic importance by the U.S. Geological Survey. They are the Lower Hartshorne, Upper Hartshorne, Charleston, and Paris coalbeds. All of them are entirely of Pennsylvanian age (Figure 2).
- Lower Hartshorne
- The Lower Hartshorne coal rests near the base of the McAlester Formation. It is the most extensive and productive coalbed in Arkansas. Underlying 1,360 square miles, it is greater than 14 inches thick over a 740 square miles area. In Sebastian County, it is up to 8 feet thick locally. Coal rank ranges from low-volatile bituminous in the western part of the Arkansas Valley coalfields to semianthracite in the eastern part.
- Upper Hartshorne
- The Upper Hartshorne coal underlies about 28 square miles of the southwestern Arkansas Valley. Low-volatile bituminous in rank, it is approximately 14 inches thick over an area of about 16 square miles, with a maximum thickness of 34 inches. It has been mined in one surface operation, located between Hartford and Huntington.
- The Charleston coalbed lies near the base of the Savanna Formation, and is 800 to 900 feet stratigraphically above the Hartshorne coalbed. The Charleston coalbed extends over an area of about 120 square miles and has been mined by many strip operations in both the east and west districts. The maximum thickness of the coalbed is about 23 inches, and it is 14 inches thick over an area of 52 square miles. In the western part of the Arkansas Valley, the coal is low-volatile bituminous in rank, whereas in the eastern part it is semianthracite. The Charleston coalbed in Franklin and Johnson Counties is known locally as the Philpott coal.
- The Paris coalbed occurs near the top of the Savanna Formation, 1,000 to 2,000 feet stratigraphically above the Hartshorne bed, underlying three small areas that total 18 square miles. The Paris coalbed ranges in thickness from 14 to 32 inches.
|Figure 1. Generalized diagram illustrating the regional distribution of the Arkansas coalfields and lignite resources (from Keystone Coal Industry Manual, 2003. This diagram was prepared by William V. Bush).|
|Table 1. Commercially Produced Coal by District|
West District (South of Arkansas River)
|Bonanza-Jenny Lind||Sebastian||Lower Hartshorne|
East District (North of Arkansas River)
|Denning-Coal Hill||Franklin-Johnson||Lower Hartshorne|
|Figure 2. Generalized stratigraphic sections in the Arkansas Valley coalfield.|