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Source map Karl, S.M., and Brew, D.A., 2002, Unpublished data.
Symbol Pal
Unit name Argillite and limestone
Description Thick limestone section includes some phyllite, slate, shale, and graywacke; limestone is thin-bedded and depositionally interbedded with other rock types; Psl unit of Brew (1997) exposed north of Casement Glacier and south of Adams Inlet, Glacier Bay. Phyllite, slate, and metagraywacke facies of Sith-gha-ee Peak Formation. Shale, siltstone, and graywacke (?) found in Muir Province. In Chilkat Mountains area includes light to medium brownish gray, fine to medium crystalline limestone that contains sparse paper thin reddish brown separations, fossiliferous, up to 15 m thick; overlain by limestone, nodular bedded, light brownish gray, fine to medium-grained limestone, 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. Part of Sith-gha-ee Peak Formation includes light and dark gray, locally fossiliferous limestone. Includes Psl of Glacier Bay (Brew, 1997). In Chilkat Mountains, in the area between Boat Harbor and William Henry Bay, and in Glacier Bay, unit includes Early Permian limestones equivalent to Halleck Formation, and Late Permian limestones equivalent to the Pybus Formation, that contain the same Septacamera brachiopods typical of the Pybus Formation, but the rocks in this area have not been subdivided. Sith-Gha-Hee unit contains Early Permian fossils and includes lithologies that are similar to the Cannery Formation. In summary, this unit includes rocks that lithologically correspond to the Halleck, Cannery, and Pybus Formations, and fossils with ages that correlate with the Halleck and Pybus Formations and the upper part of the Cannery Formation
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