REMARKS: Massive outcrops of albite-chlorite schist of the Wissahickon Formation (Precambrian (?) age) in a narrow gorge of the West Branch produce a highly scenic setting. A public spring marked "Black Rock" is nearby.
REMARKS: A magnificent anticline of Lower Cambrian Chickies Quartzite is exposed along the Susquehanna River at the west end of Chickies Ridge. This is also the site of a fine overlook and picnic area atop the anticline. The Chickies Quartzite contains rare animal borings, or tubes, called "scolithus tubes"; these were once thought to be a Cambrian-age marine worm, Scolithus.
REFERENCES: Frazer, Persifor, Jr. , The geology of Lancaster County, Pennsylvania Geological Survey, 2nd ser., Report CCC, 350 p.
Goodwin, P. W., and Anderson, E. J. , Associated physical and biogenic structures in environmental subdivision of a Cambrian tidal sand body, Journal of Geology, v. 82, p. 779-794.
Stose, G. W., and Jonas, A. I. , Geology and mineral resources of the Middletown quadrangle, Pennsylvania U. S. Geological Survey Bulletin 840, 86 p.
PHOTO: ©2004 Kurt Enck.
REMARKS: South of the Holtwood Dam there are over 60 islands. In contrast to the others in the river, which are alluvial in nature, the Conowingo Islands are erosional remnants of the metamorphic rocks (schists and gneisses) of southern Lancaster County. This group of islands represents one of the most scenic areas of the state. The larger islands are:
356. Upper Bear Island: the largest of the group and the most primitive; has ridges of bedrock.
357. Lower Bear Island: second in size; the northern third is very rocky and has sheer-walled old channels, and ponds and marshes.
358. Piney Island: the northernmost of the group and immediately south of the Holtwood Dam; about half of the island is exposed rock.
359. Brushy Island: this and the cluster of islands immediately west of Piney Island are aptly named; very brushy; contains large exposures of Wissahickon Schist (Precambrian (?) age).
360. Peavine, 361. Wildcat, and 362. Crow Islands : these islands and lesser ones total about 35 acres and are north and west of Upper Bear Island and immediately downstream from the Norman Wood Bridge; they are low, rocky islands.
363. Deepwater and 364. Turkey Islands: two small areas east of the Bear Islands and very close to the York County Shoreline.
365. Little Chestnut, 366. Wolf, 367. Sicily, and 368. Beach Islands : a scattered cluster near Big Chestnut and Hennery Islands; these small islands are especially scenic because of their spectacular high cliffs.
369. Mount Johnson Island: the southernmost island of the group; it towers 200 feet above the river and is very rugged.
REMARKS: Outcrops of quartz conglomerate of the Hammer Creek Formation (Triassic age); one outcrop has weathered unevenly and now resembles the shape of an eagle.
PHOTO: ©2004 Kurt Enck.
REMARKS: Magnificent view of the Susquehanna River valley, in an area known as the "river hills." These "hills" are underlain by schists of the Wissahickon Formation (Precambrian(?) age). Piney Island, one of the Conowingo Islands, lies directly below the overlook. An actual topographic cliff of schist known as Face Rock (372) is approximately 1.6 miles south of this overlook.
REMARKS: Limited genera and individuals in a Lower Cambrian shaly siltstone (Kinzers Formation). Outstanding examples of two trilobite genera, Paedumias and Olenellus, are found; a site of the oldest fossils found in Pennsylvania.
REMARKS: A unique site of Lower Cambrian fossils, chiefly trilobites; the site from which an almost 500-specimen collection came, now at the Peabody Museum (Yale University); the type locality for the trilobite Olenellus getzi. Trilobites are present in shale of the Kinzers Formation.
REFERENCES: Dunbar, C. O. (1925), Antennae in Olenellus getzi, new species, American Journal of Science, Fifth Series, v. 9, no. 52, p. 303-308.
REMARKS: Before 1800 a notorious horse thief known as "The Governor" established his headquarters here. Another legend has it that the cave was visited by Andrew Curtin, Governor of Pennsylvania from 1861 to 1867, who took shelter here with his aides during a storm while traveling the Falmouth-Elizabethtown Pike on the way from Lancaster to Harrisburg. This is a boulder cave made up of two large boulders capped by a third boulder, surrounded by other boulders; it has a convenient natural chimney. The rounded boulders are composed of Triassic diabase (commonly called ironstone).
REFERENCES: Bolles, W. H. , Governor's Stables, Pennsylvania Geology, v. 9, no. 1, p. 6-7.
Reich, J. R., Jr.  Caves of southeastern Pennsylvania, Pennsylvania Geological Survey, 4th ser., General Geology Report 65, p. 27.
REMARKS: Kellys Run flows through a very wild and rocky gorge in the Wissahickon Schist (Precambrian(?) age). Sheer, vertical rock walls occur through the gorge.
REMARKS: An excellent view of the river to the north; islands, Lake Aldred, and the "river hills" in the Wissahickon Schist (Precambrian(?) age). A plaque at the site reads: "In 68 miles the Susquehanna River falls 295 feet."
REMARKS: A series of extremely large potholes in diabase (Triassic age) in the bed of the Susquehanna River; visible yearly at low water levels.
REFERENCES: Beck, H. H. , Prolonged drouth uncovers geologic phenomenon, Pennsylvania Department of Internal Affairs Bulletin, v. 16, no. 2, p. 3-6.
___________ , The pot holes of Conewago Falls, Pennsylvania Academy of Science Proceedings, v. 22, p. 127-230.
Myers, R. E. , The Conewago pot holes of the Susquehanna River, Pennsylvania Angler, v. 22, no. 10, p. 6-9, 25-27.
REMARKS: An excellent view of the Conowingo Islands in the Susquehanna from this pinnacle of Peters Creek Schist (Precambrian age). The northwest side of the park boundary follows Wissler Run and includes a very steep, rocky north slope (Peters Creek Schist). The three-unit facility of the Peach Bottom Nuclear Plant (one of the largest in the world) may be viewed from this site.
REMARKS: An extremely scenic glen carved into the Wissahickon Schist (Precambrian(?) age); wild, wooded, and remote.
REMARKS: Chromite was mined here in the early 1800's. The Wood Mine was the largest and most famous of many chromite mines in the southeastern Pennsylvania. This mine supplied nearly 100 percent of the world's chrome ore prior to the Civil War.
REFERENCES: Lapham, D. M. , Preliminary report on the chromite occurrence at the Wood mine, Pennsylvania, Pennsylvania Geological Survey, 4th ser., Progress Report 153, 11 p.
Pearre, N. C., and Heyl, A. V. , The history of chromite mining in Pennsylvania and Maryland, Pennsylvania Geological Survey, 4th ser., Information Circular 14, 27 p.