USGS - science for a changing world

Mineral Resources On-Line Spatial Data

Beekmantown Group

Beekmantown Group - Includes, in descending order, the Pinesburg Station (Ops), Rockdale Run (Orr), and Stonehenge (Os) Formations.
StatePennsylvania
NameBeekmantown Group
Geologic ageOrdovician
Original map labelOb
CommentsSecondary unit description from USGS Geologic Names lexicon (ref. PA003): [Pinesburg Station ] Named Pinesburg Station dolomite for Pinesburg Station, Washington, Co., MD. Unit is a succession of dolomites overlying the Rockdale Run formation and underlying the Row Park limestone. Formation averages about 450 feet thick and the top of the Pinesburg Station is placed at the base of the lowest limestone bed in the overlying Row Park. The lack of fossils in this unit makes it difficult to date, however, correlation to sections in PA suggest that the Lower-Middle Ordovician boundary is near the top of the Pinesburg Station dolomite and is therefore tentatively placed at the top of the formation. [Rockdale Run Formation] Named Rockdale Run formation of the Beekmantown group for Rockdale Run, near Hicksville, Washington Co., MD. Consists of interbedded limestones and dolomites overlying the Stonehenge limestone. The lower two-thirds of the formation is predominantly limestone, while dolomite dominates the upper third. The top of the Rockdale Run is placed at the top of the highest limestone bed beneath the Pinesburg Station dolomite. The formation averages about 2450 feet thick. A number of faunal zones may be useful for local and regional correlation including the LECANOPIRA zone (200-560 feet above base), the ARCHAEOSCYPHIA zone (560-790 feet above base), the DIPARELASMA zone (790-1420 feet above base), and the SYNTROPHOPSIS-CLELANDOCERAS zone (1650-2070 feet above base). The formation is considered of Early Ordovician age. [Stonehenge Formation] Named for the community of Stonehenge, just east of Chambersburg, Franklin Co., PA. Consists of a lower dark to light gray limestone with sandy laminae less developed than overlying beds and an upper fine-grained light to dark gray limestone containing contorted laminae of sandy matter that stand in relief or fall to sandy shale on weathering and thick beds of "edgewise" conglomerate. 485 feet thick. Overlies Conococheague limestone; underlies remainder of Beekmantown limestone. Report contains measured section of Beekmantown limestone. Considered of Ordovician age.
Primary rock typelimestone
Secondary rock typedolostone (dolomite)
Other rock typeschert
Lithologic constituents
Major
Sedimentary > Carbonate > Limestone (Bed)
Minor
Sedimentary > Carbonate > Dolostone (Bed)Ops and Orr
Incidental
Sedimentary > Chemical > Chert (Bed)Orr
Map references
Pennsylvania Bureau of Topographic and Geologic Survey, Department of Conservation and Natural Resources, 2001, Bedrock Geology of Pennsylvania, edition: 1.0, digital map. Retrieved from internet 9-30-2004; <http://www.dcnr.state.pa.us/topogeo/map1/bedmap.aspx> DL Data: pageoexp.zip
Unit references
Berg, T. M., Edmunds, W. E., Geyer, A. R., and others, compilers, 1980, Geologic map of Pennsylvania: Pennsylvania Geological Survey, 4th ser., Map 1, 2nd ed., 3 sheets, scale 1:250,000.
Pennsylvania Bureau of Topographic and Geologic Survey, Department of Conservation and Natural Resources, 2001, Bedrock Geology of Pennsylvania, edition: 1.0, digital map. Retrieved from internet 9-30-2004; <http://www.dcnr.state.pa.us/topogeo/map1/bedmap.aspx> DL Data: pageoexp.zip
USGS Geologic Names Lexicon (GEOLEX)
Geographic coverageAdams - Berks - Bucks - Lehigh

Show this information as [XML] - [JSON]

AccessibilityFOIAPrivacyPolicies and Notices

Take Pride in America logoUSA.gov logoU.S. Department of the Interior | U.S. Geological Survey
URL: http://mrdata.usgs.gov/geology/state/sgmc-unit.php?unit=PAOb;20
Page Contact Information: Peter Schweitzer