Named the Eyer member of the Hatter formation for Eyer, Huntingdon Co., south-central PA. Unit is lowest member of Hatter formation. Consists of dark impure limestone and calcarenite. Thickness is 6 feet at type locality. Overlies Clover member of Loysburg formation and underlies Grazier member of Hatter. The Eyer is of Middle Ordovician age.

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

Raised the rank of the Eyer to the Eyer formation of the Hatter group in PA.

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

The Hatter Formation has been recognized throughout the Valley and Ridge province in central PA, but changes character in the extreme northeast. According to Wagner (1966), it extends in the subsurface to WV. Unit consists of a basal fossiliferous limestone, overlain by fine-grained limestone containing shaly partings, which in turn is overlain by fucoidal, fossiliferous magnesian limestone. The basal Eyer Member is composed of fossiliferous, medium- to thick-bedded calcarenites interbedded with medium-bedded calcilutites and thin, irregular shaly partings. The middle Grazier Member consists of medium-dark-gray, medium- to thick-bedded calcisiltite and calcilutite. Upper Hostler Member is coarser grained than the Grazier, consisting mostly of calcisiltite and thin interbeds of calcarenite. Eyer Member of the Hatter conformably overlies the Loysburg Formation. Contact is placed at the base of the first fossiliferous calcarenite of the Eyer Member. The Eyer Member is 3.4+/-0.4 m, the Grazier Member is 14.6+/-2 m, and the Hostler Member is 12+/-2 m thick. No basis given for Late Ordovician age assignment. [No mention of Black River Group.]

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