Little Mountain forms a small, secondary ridge parallel to and lying along the northern base of Blue Mountain where Susquehanna River has cut its water gap through the ranges north of Harrisburg, Pennsylvania. This topographic feature appears first about 2 miles east of the Susquehanna, and continues westward beyond the river into Perry County. Its development suggests some structural peculiarity. At the crest of Little Mountain west of Susquehanna River occur beds here assigned to the Oriskany, although the bulk of this ridge is composed of Middle Devonian strata. The presence of the Oriskany is significant since the absence of Lower Devonian and adjacent beds at Susquehanna Gap has been generally accepted. This absence has been attributed either to nondeposition locally or to subsequent faulting out of any of those beds which may have been deposited, or to a combination of these causes.
Geology of the Susquehanna Gap Region . . .