Cannery Formation and Porcupine slate of Redman and others (1985), undivided

Unit symbol: PDcf
Age range Permian to Devonian (419.2 to 272.3 Ma)
Lithology: Sedimentary
Group name: Cannery Formation and Porcupine slate of Redman and others (1985), undivided
Cherty graywacke and argillite that contains subordinate conglomerate, limestone, and volcanic rock interbeds; locally metamorphosed to slate, phyllite, marble, greenstone, and hornfels; intensely folded (Loney, 1964; Lathram and others, 1965; Muffler, 1967; Brew and others, 1984; Redman and others, 1985; Karl and others, 2010). Includes the Porcupine slate of Redman and others (1985) and undifferentiated chert, marble, and argillite mapped by Gilbert (1988). Graywacke, tuff, and chert are commonly interbedded, deposited as turbidites. Graywacke beds are up to 5 m thick and dominantly consist of volcanic and calcareous rock fragments. Limestone occurs in beds up to 50 cm thick, and pillow basalt and tuff-breccia horizons are as thick as 100 m. Total thickness of the Cannery Formation is estimated to be greater than 500 m (Karl and others, 2010). Limestone of the Cannery Formation contains Permian bryozoans and crinoids on Admiralty Island (Lathram and others, 1965). Chert contains Mississippian to Permian radiolarians (Karl and others, 2010). On Kupreanof Island, chert and limestone contain Early Pennsylvanian to early Permian radiolarians, early Permian conodonts, and Upper Mississippian conodonts (Karl and others, 1999). Here, also includes calcareous schist and semischist on northwestern Admiralty Island that were previously mapped as part of the Retreat Group by Lathram and others (1965). The Cannery Formation is likely correlative with the Porcupine slate of Redman and others (1985) (unit |ps). Also included here is a unit of siliceous phyllite and metachert on Admiralty Island of similar age to rocks at the base of the defined Cannery Formation (Karl and others, 2010) of Late Devonian age. Co-author S.M. Karl considers these siliceous phyllites and metacherts to be a separate unit, but we include them here

Source map information

Source map Karl, S.M., Haeussler, P.J., and McCafferty, Anne, 1999, Reconnaissance geologic map of the Duncan Canal-Zarembo Island area, southeast Alaska: U.S. Geological Survey Open File Report 99-168, 1 sheet, scale 1:125,000.
Symbol PMc
Unit name Cannery Formation
Description Gray chert, green chert, red chert, black cherty argillite, gray and green slatey argillite, gray silicified limestone, black siltstone and chert turbidites, graywacke turbidites, minor conglomerate, conglomeratic debris flows, tuff, and volcanic rocks.
Lithology Metamorphic

Correlated geologic units

Label PDcvs
Description Cannery Formation, metasedimentary and metavolcanic rocks, undivided
Geologic age Late-Devonian to Cisuralian
Geologic setting Undivided
Lithology Form Importance
Metasedimentary < Metamorphic Major
Metavolcanic < Metaigneous < Metamorphic Indeterminate, major