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The 240-square-mile area described in this report includes the Ivydell, Jellico 'Vest, Ketchen, and Pioneer 7lh-minute quadrangles in Scott and Campbell Counties, Tenn., and McCreary and Whitley Counties, Ky. Elk Yalle.y, the source of the area name, is centrally located.The quadrangles of this report are in the Cumberland Mountain section of the Appalachian Plate-aus province, except for the southeast co•rner of the Ivydell quadrangle which is in the Valley and Ridge province. That part of the area in the Cumberland Mountain section lies within the gently folded Cumberland overthrust sheet where the principal streams flow parallel to ridges that fringe the blunt southwest end of the Middlesboro syncline. Northwest and •southwest of the Cumberland overthrust sheet, the Cumberland Mountain section is characterized by dendritic drainage patterns that were incised into relatively flat-lying rocks.The rock formations exposed in the Elk Valley area range from the Newala Dolomite of Early Ordovician age to the Hignite Formation of Middle Pennsylvanian age. Approximately the lower third of this sequence consists of ca•rbonate rocks of Early and Middle Ordovician age that crop out in the extreme southeast corner of the area. The middle third of the sequence is composed of alternating beds of shale and carbonate rocks of Late Ordovician to Early Mississippian age that crop out in narrow belts of upturned beds on the limbs of the MiddleSJboro syncline and along the Pine Mountain fault zone. Strata in the upper third of the section consist principally of sandstone, siltstone, shale, and coal of Late Mississippian and Pennsylvanian age, which are at the surface in most of the report area. These upper strata are largely of continental origin and vary more laterally than do the underlying formations of marine origin. The sequence totals a'bout 8,300 feet in thickness and haSI been divided into 25 mapped formations. An additional 3,500 feet of underlying strata in the subsurface has been assigned to six formations that range in age from Early Cambrian to Early Ordovician. Unconsolidated surficial deposits of Quaternary age locally cover the bedrock.The gentle southeasterly dip of strata, away from the Cincinnati arch, is terminated in the Elk Valley area by faulting and folding at the pe.riphery of the Cumberland overthrust sheet. During late-or post-Paleozoic deformation of the Appalachian geosyncline the overthrust sheet was di>splaced northwestward by overthrusting on the Pine Mountain fault and by strike-slip movement along the Jacksboro fault. The thickness and character of formations on opposite sides of the Jacksboro fault indicate approximately 11 miles of movement at the southwest end of the overthrust sheet. Because of southeastward thickening of the stratigraphic section, northwestward movement of the overthrust sheet has placed a relatively thicker ,section of rocks opposite its counterpart across the Jacksboro fault. As a result of this thickening and subsequent displacement, 'beds cropping out in the Middlesboro ....

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The Pocahontas Formation is a clastic wedge of sandstone, siltstone, shale, coal, and underclay that is transitional between underlying marine strata of Mississippian age and overlying continental beds of Pennsylvanian age. It attains a maximum thickness of 750 ft. at the southeastern edge of the Appalachian coal field and thins northwestward by the tonguing out of lower beds and by the truncation of upper beds at an overlying unconformity.Sandstone, which composes about 70 percent of the formation, occurs in lenticular bodies that have two distinct distribution patterns-lobate and linear-of contrasting orientation and composition. The lobate bodies are elongate to the northwest and contain sandstone having a quartz content of about 50 to 65 percent. Within a lobe, thickness lines show a northwestward bifurcating pattern similar to the pattern of channels in an alluvial distributary system of a modern delta. Laterally, lobate bodies merge to form northwestward-thinning sandstone wedges as much as 300 ft. thick. The linear pattern is shown by 3-to 8-mi.-wide sandstone lenses that extend north-northeast for about 45 mi. They are near the distal ends of the lobate sandstone and consist of 0 to 140 ft. of relatively pure quartzose sandstone. The well-washed character and orientation of the linear bodies, normal to the lobate bodies, indicate a barrier-bar origin.These sediment distribution patterns show that the Pocahontas Formation was deposited mainly in deltaic complexes built out from the southeast during marine regression to the northwest. Brief periods of transgression and stable shoreline conditions are recorded by tongues of marine strata and by the barrier bars. 31 32 KENNETH J. ENGLUND

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