ABSTRACT
The present paper is a preliminary summary of the Beekmantown succession established by the writer in Berks County, Pennsylvania. In the Reading Quadrangle, near the Schuylkill River, four mappable rock formations could be differentiated readily in the Beekmantown limestone, thus raising the name Beekmantown to the rank of group in that area. This paper summarizes the diagnostic rock characters of the units at the chosen type sections and introduces new names for three of the formations. The formations and their thicknesses at or near the type sections are as follows in descending order.
| . | Feet . |
|---|---|
| Lower Ordovician series, Beekmantown group | |
| Ontelaunee (new name) dolomite with interbedded limestone and chert.................... | 675 |
| Epler (new name) interbedded limestone and dolomite........................................ | 800 |
| Rickenbach (new name) fine-grained and coarse-grained dolomite........................ | 580 |
| Stonehenge limestone and interbedded dolomite.................................................. | 250 |
| Total thickness.................................................... | 2,305 |
| . | Feet . |
|---|---|
| Lower Ordovician series, Beekmantown group | |
| Ontelaunee (new name) dolomite with interbedded limestone and chert.................... | 675 |
| Epler (new name) interbedded limestone and dolomite........................................ | 800 |
| Rickenbach (new name) fine-grained and coarse-grained dolomite........................ | 580 |
| Stonehenge limestone and interbedded dolomite.................................................. | 250 |
| Total thickness.................................................... | 2,305 |
Lithologic subdivisions or members are recognized in the formations. A columnar section summarizes the diagnostic rock characters of the members in Berks County. General rock equivalents of the formations in central Pennsylvania and in western Vermont are indicated.
