Basal limestone of Walloomsac contains pelmatozoans, bryozoans, algae remains, and conodonts. Conodonts exposed at No Bottom Pond indicate a Middle Ordovician or slightly younger age (according to J. Huddleston, USGS). Age of whole unit is Middle and Late(?) Ordovician.

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

Pg. 15, geologic time scale (inside front cover). Walloomsac Formation (Middle Ordovician). Sample from staurolite-garnet schist, at Lat. 41 deg. 59 min. 45 sec. N., Long. 73 deg. 25 min. 00 sec. W., Sharon quadrangle, Litchfield County, Connecticut, yielded a Rb-Sr age of 368 +/-19 Ma (biotite). Age recalculated, using decay constants of Steiger and Jager, 1977 (Earth Planet. Sci. Letters, v. 36, p. 359-362), from Zen and Hartshorn's (1966) published age of 355 Ma for this sample. Zartman and others (1970) reported a K-Ar age of 390 Ma (muscovite). Initial age of schist (Middle Ordovician) disturbed by later metamorphism [Devonian].

Source: Publication.

Used as Walloomsac Formation of Middle Ordovician age. Mapped as one main unit and three informal, unnamed subunits. Subunit consisting of tan to dark-blue laminated quartzite and calcareous quartzite was previously mapped by other workers as Bellowspipe Quartzite [name not used on this map].

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

In this map area, Manhattan Schist member A is replaced by Walloomsac Formation based on work by Jackson and Hall (1982), Hall (in press), and A.A. Drake (1990., pers. commun.).

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

Thin limestone unit near base of Walloomsac locally contains abundant bryozoan fragments, cup corals, pelmatozoan hash, and conodonts that indicate that the base of the Walloomsac is Rocklandian (middle and late Caradocian) or younger. Age of unit is Middle Ordovician.

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