Beekmantown Group

Includes, in descending order, the Ontelaunee (Oo), Epler (Oe), Rickenbach (Ori), and Stonehenge (Os) Formations.
State Pennsylvania
Name Beekmantown Group
Geologic age Ordovician
Lithologic constituents
Sedimentary > Carbonate > Limestone (Bed)Oe and Os
Sedimentary > Carbonate > Dolostone (Bed)
Sedimentary > Chemical > Chert (Lens)Oo and Ori
Sedimentary > Clastic > Conglomerate (Bed)Oe and Os
Comments Secondary unit description from USGS Geologic Names lexicon (ref. PA003): [Ontelaunee Formation] Name Ontelaunee formation proposed for the dolomite and interbedded limestone and chert lying above Epler formation (new) and underlying either Annville limestone, Jacksonburg argillaceous limestone, or Martinsburg shale. Formation is 675 ft thick near type locality and is divided into three unnamed members: upper interbedded limestone and dolomite member, middle dolomite member, and lower interbedded chert and dolomite member. Thins to 150 to 250 ft near Reading. Contact with Epler is placed at top of first limestone beneath lowest chert bed of Ontelaunee. Contact zone is gradational. Line demarcating contact in Berks Co. is placed 100 ft below lowest chert bed of Ontelaunee. Age is Early Ordovician. [Epler Fromation] Name Epler formation proposed in southeastern PA for interbedded limestone and dolomite overlying Rickenbach formation (new) and underlying dolomite beds here termed Ontelaunee formation. Divided into two unnamed members: upper characterized by large proportion of calcarenite with bioclastics and limestone pebbles, and lower in which calcilutite is common. Both members contain interbedded dolomite with much larger percentage in lower member. Thickness 800 ft in type section. Contact with underlying Rickenbach is transitional, and boundary set at base of first limestone above solid dolomite body of the Rickenbach. Contact with overlying Ontelaunee is placed at top of first limestone bed beneath lowest chert bed of Ontelaunee, and in Berks Co. this contact is 100 ft below lower chert bed. Contact zone is gradational. Age is Early Ordovician. [Rickenbach Formation] Name Rickenbach proposed for thick- to thin-bedded fine-grained and coarse-grained dolomite overlying Stonehenge limestone and underlying interbedded limestone and dolomite here referred to as Epler formation. Upper and lower contacts transitional. Consists of two unnamed members, an upper fine-grained and a lower coarse-grained. Total thickness about 580 ft. Type sections for both members given.

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, Miles, C.E., and Whitfield, T.G., compilers, 2001, Bedrock Geology of Pennsylvania, edition: 1.0, digital map, scale 1:250,000.

USGS Geologic Names lexicon found at:

NGMDB product
Counties Berks - Bucks - Lehigh