 Five major rock formations are present in Leonard Harrison State Park , from the Devonian and Carboniferous periods . The youngest of these , which forms the highest points in the park and along the gorge , is the early Pennsylvanian Pottsville Formation , a gray conglomerate that may contain sandstone , siltstone , and shale , as well as anthracite coal . Low @-@ sulfur coal was once mined at three locations within the Pine Creek watershed . Below this is the late Mississippian Mauch Chunk Formation , which is formed with grayish @-@ red shale , siltstone , sandstone , and conglomerate . <unk> were once carved from the exposed sections of this conglomerate . Together the Pottsville and Mauch Chunk formations are some 300 feet ( 91 m ) thick . 
