The Cumberland Gap coal field lies in Bell and Harlan counties, in the southeast corner of Kentucky and in Claiborne and Campbell counties, Tenn., and extends in a general northeast-southwest direction between Pine and Cumberland mountains from Fork Mountain on the southwest to the heads of Poor and Clover forks of Cumberland River on the northeast. As defined in this paper, it has a total length of about 90 miles and a width of from 15 to 20 miles. (See Pl. II.)
In this paper is described only the central part of the basin, or the area lying between Log Mountains at the head of Yell ow Creek of Cumberland and nearly north-south line about 10 miles east of Harlan, and while the data presented will give an idea of the general stratigraphy and structure of the whole field, they are not authoritative except within these limits.