Berkshire Valley Formation is here proposed for sequence of strata at Longwood Lake, NJ, previously mapped as Decker Formation by Kummel and Weller (1902) and Weller (1903). Unit is composed predominantly of gray to greenish gray fossiliferous, calcareous siltstone with abundant lenses and beds of medium gray, fossiliferous, sublithographic, silty dolomite. Both rock types weather yellow gray. At the type section, unit conformably overlies the Poxono Island Formation and disconformably underlies the Connelly Conglomerate. The Berkshire Valley is known only in the southern part of the Green Pond-Schunemunk Mountain outlier. Measures 126 ft at Longwood Lake, the only complete section. Large glacial erratics of the Berkshire Valley are scattered over a large area from 1 to 2 mi northeast of Green Pond, NJ. Correlates with the entire Clove Brook Member of the Decker Formation at Nearpass Quarry.

Source: GNU records (USGS DDS-6; Reston GNULEX).

The Berkshire Valley Formation in the Green Pond Mountain region consists of yellowish-gray weathering, medium-gray to pinkish-gray, very thin- to thin-bedded, fossiliferous limestone with interbedded gray to greenish-gray calcareous siltstone and silty dolomite, medium-gray to light-gray dolomite conglomerate, and grayish-black, thinly laminated shale. Thickness is 27 to 38 meters. Conformably overlies the Poxono Island Formation and unconformably underlies the Connelly Conglomerate. The Berkshire Valley Formation is of Late Silurian age.

Source: GNU records (USGS DDS-6; Reston GNULEX).