REMARKS: A spectacular "wall" of outcrop of Sharp Mountain quartz-pebble conglomerate (Pottsville Group, Pennsylvanian age). The "wall" has also been known as High Rocks and Boxcar Rocks.
PHOTO: © Michael Lane.
REMARKS: An igneous, diabase layer of Triassic age intruded a sequence of limestone layers. Iron-rich solutions replaced the limestone bedrock and deposited a large iron ore body that had a wide variety of minerals. Mined from 1742 to 1973, it was the oldest continuously operated mine in the United States. The mine provided cannon shot and cannons for the Revolutionary War.
REFERENCES: Gray, Carlyle, and Lapham, D. M. , Guide to the geology of Cornwall, Pennsylvania, Pennsylvania Geological Survey, 4th ser., General Geology Report 35, 18 p.
Lapham, D. M. , Cornwall: the end of an era, Pennsylvania Geology, v. 3, no. 5, p. 2-5.
Lapham, D. M., and Gray, Carlyle , Geology and origin of the Triassic magnetite deposit and diabase at Cornwall, Pennsylvania, Pennsylvania Geological Survey, 4th ser., Mineral Resource Report 56, 343 p.
REMARKS: A local name applied to an erosional remnant of a Triassic-Jurassic diabase sheet. The diabase of this large intrusion is a medium- to coarse-grained, dark-gray rock having ophitic texture. The rock in the outcrop is very massive and usually weathers into large spheroidal boulders.
PHOTO: © Michael Lane.
REMARKS: The hard, resistant quartzite and conglomerate of the Hardyston Formation (Cambrian age) underlie this feature and account for its high relief (1300 feet above sea level). Numerous exposures of quartzite on the summit have weathered into various shapes.
REMARKS: Schaefferstown Spring issues from the limestone conglomerate of the Hammer Creek Formation (Triassic age). The yield is usually less than 10 gallons per minute. This spring was deeded from Alexander Schaeffer to the residents of Market Street on July 16, 1763. The water is now piped from the spring to a fountain near the spring and to two fountains on Market Street. The water flows by gravity from the spring in Fountain Park to the fountains.
It is the oldest chartered waterworks in the United States.
REFERENCES: Gray, Carlyle, Geyer, A. R., and McLaughlin, D. B. (1958), Geology of the Richland quadrangle, Pennsylvania Geological Survey, 4th ser., Atlas 167, scale 1:24,000.
Thomas R. Brendle Museum of Historic Schaefferstown, Inc., Schaefferstown, Pa.
PHOTO: Left - Spring in Fountain Park; Right, top and bottom - Fountains on Market Street. © Randy E. Newcomer 12/30/01.
REMARKS: An outcrop of Ordovician shale containing the largest abundance of the trilobite Cryptolithus in Pennsylvania; also contains excellent specimens of the rare Ordovician starfish Hallaster.
REFERENCES: Hoskins, D. M. , Fossil collecting in Pennsylvania, Pennsylvania Department of Geological Survey, 4th ser., General Geology Report 40, 2nd printing, revised 126 p.
Cramer, H. R. , Ordovician starfish from the Martinsburg Shale, Swatara Gap, Pennsylvania, Journal of Paleontology, v. 31, p. 903-907.
UPDATE: The PA Geological Survey has listed this site as "extinct" since it was partially covered in the process of bridge construction. Much of the material was relocated as described in the link below. [09/03/09]
Swatara Gap Fossil Migration - PAGS page on the transfer of material from the orginal site. [09/03/09]