Pybus Formation and correlative? limestone

Unit symbol: Plps
Age range Permian (298.9 to 259.9 Ma)
Lithology: Sedimentary
Group name: Limestone and calcareous clastic rocks
Characteristically “light-brownish-gray to white, medium-bedded, fossiliferous, fine- to medium-grained dolomite [dolostone], which contains irregular layers and scattered angular fragments of bluish-white chert. The chert content increases upward and near the top of the formation constitutes as much as 90 percent of the rock” (Lathram and others, 1965). On northern Kuiu and Kupreanof Islands and Admiralty Island, unit consists of medium-bedded dolostone, limestone, and subordinate gray chert beds and nodules (Lathram and others, 1965; Muffler, 1967; and Brew and others, 1984). The Pybus Formation contains very late early Permian conodonts (Premo and others, 2010), Cisuralian (early Permian) brachiopods (Muffler, 1967; Brew and others, 1984), and Guadalupian (middle Permian) conodonts (Karl and others, 1999). In the Glacier Bay area, light- to medium-brownish-gray, fine- to medium-grained crystalline, fossiliferous limestone contains sparse, paper-thin, reddish brown separations and is overlain by nodular bedded, light-brownish-gray, fine- to medium-grained limestone interbedded with light-greenish-brown chert. The upper limestone and chert varies along strike from an interbedded sequence to apparent limestone-chert conglomerate, which is, in turn, overlain by dark-gray slate, interbedded with very fine-grained and silty calcareous graywacke (Brew and Ford, 1985)

Source map information

Source map Brew, D.A., and Ford, A.B., 1985, Preliminary reconnaissance geologic map of the Juneau, Taku River, Atlin, and part of the Skagway 1:250,000 quadrangles, southeastern Alaska: U.S. Geological Survey Open-File Report 85-395, pamphlet 23 p., 2 sheets, scale 1:250,000.
Symbol Pul
Unit name Limestone and siltstone
Description ALEXANDER BELT: UNNAMED PERMIAN FORMATION(S) IN GLACIER BAY-CHILKAT MOUNTAINS AREA Thin to thick bedded, locally cherty, light to dark gray. Described by Lathram and others (1959) as: "Limestone-- Light to medium brownish gray, fine to medium crystalline, contains sparse paper thin reddish brown separations, fossiliferous, 50(?) feet thick; overlain by limestone, nodular bedded, light brownish gray, fine to medium grained, interbedded with light greenish brown chert, which varies along strike from interbedded sequence to apparent limestone chert conglomerate; in turn overlain by dark gray slate, interbedded with very fine grained calcareous graywacke and silty calcareous graywacke."
Lithology Sedimentary

Correlated geologic units

Label Psfl
Description Limestone of Sitth-gha-ee Peak formation of Brew (1997)
Geologic age Permian to Guadalupian
Geologic setting Sedimentary, carbonate
Lithology Form Importance
Limestone < Carbonate < Sedimentary Calcareous Major