Site Locations: (5)                                                           

Indigo Tunnel, mileage 140.03

          Nearest Access: Fifteen Mile Creek Camp, mileage 140.77

 Little Orleans, mileage 142.25

           Nearest Access: Fifteen Mile Creek Camp, mileage 140.77

Four Mile Level, mileage 153.01

           Nearest Access: Outdoor Club Road, mileage 153.28                                                 

Tunnel Hill, mileage 155.20/155.80

           Nearest Access: Paw Paw Tunnel Parking Lot, mileage 156.20                                       

Lock 67, mileage 160.60

          Nearest Access: Lock 67, mileage 161.76

  This thick assemblage of thin to medium bedded marine sandstones, interbedded with marine siltstone layers, becomes coarser grained upwards terminating in a quartz pebble conglomerate. In other regions of the eastern U.S. this formation is known as the Chemung.  Here it is named for the more locally occurring exposures along the Foreknobs ridge in West Virginia.  The Foreknobs is defined by the abundance of sandstone layers while its adjacent formation, the Brallier-Sherr, is predominantly a siltstone formation, notably lacking in sandstone.  However, the rocks grade into each other such that a definitive boundary is not easily recognized.  This is an issue at Paw Paw tunnel.  The excavation was primarily in siltstone but the ridge called Tunnel Hill is capped by Foreknobs and it can also be observed at river level parallel to the tunnel where sandstone layers slant upwards to form an anticline arching over the tunnel.

  One of the most interesting segments of the Canal geologically is that which includes the Four Mile Level site but continues down stream to Bond’s Landing and upstream to Sorrel Campground a distance of about 4 miles.  A succession of folds is the prime attraction.  Also the segment from the Little Orleans site upstream through Devil’s Alley is very rewarding for the spectacular cliffs, a mileage distance of about 2.4 miles.

  The Foreknobs was deposited in an environment that was most conducive to marine life, therefore, it is perhaps the most fossiliferous of the rock formations along the Canal.  Next to the Mississippian age clastic deposits such as the Rockwell, Foreknobs is the most divers in terms of genus and species varieties.  One particular fossil, Cyrtospirifer disjunctus, is recognized as an index fossil meaning that when it is discovered, as it was atop Tunnel Hill, it explicitly defines the Chemung, a.k.a. Foreknobs.  Fossilized crinoids, brachiopods, pelecypods, gastropods, and cephalopods can all be found in the Foreknobs.  However, be aware that only ‘eyeballing’ the rock surfaces for fossil evidence is permitted by Federal law within National Park boundaries.

Top of Page