Oakdale Formation

Metamorphosed thin-bedded, pelitic and calcareous siltstone and muscovite schist, probably low-grade equivalent of Paxton Formation. The Oakdale Formation is here revised to include strata previously mapped in CT and adjacent MA as the Hebron Formation and the Scotland Schist. The Scotland Member (Pease, 1980) is renamed the Scotland Schist Member of the Oakdale. The Oakdale is a homogeneous, calcareous metasiltstone at the base of a thick stratigraphic sequence in a geosyncline terrane and extends from NH to the Honey Hill fault in eastern CT. In central eastern CT it underlies the Hebron Formation; in northeast CT and adjacent MA it underlies conformably the Dudley Formation of the Paxton Group; in central MA it underlies the Paxton Group undivided. The lower part of the Oakdale is cut out along the Clinton-Newbury fault zone. Thickness in type area is about 1500 m. Correlative with the Gove Member of the Berwick Formation in NH and the Gonic Formation in ME. Age is Late Proterozoic(?) based on intrusion of 440 Ma Hedgehog Hill gneiss in the upper part of the Brimfield Group at the top of the stratigraphic sequence, and an age of 1188 Ma for detrital zircons from the Paxton in north-central MA (Pease, 1989).
State Massachusetts
Name Oakdale Formation
Geologic age Silurian
Lithologic constituents
Major
Metamorphic > Schist > Mica-schist > Muscovite-schistMetamorphosed thin-bedded, pelitic and calcareous siltstone and muscovite schist, probably low-grade equivalent of Paxton Formation.
Metamorphic > MetasedimentaryMetamorphosed thin-bedded, pelitic and calcareous siltstone and muscovite schist, probably low-grade equivalent of Paxton Formation.
Comments Part of Merrimack Belt (Silurian, Devonian and Pennsylvanian Rocks). Secondary unit description per MA009.
References
NGMDB product
Counties Middlesex - Worcester