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Source map Karl, S.M., 2002, Unpublished data.
Symbol PDc
Unit name Cannery Formation
Description Gray, brown, green, maroon, and tan argillite, chert, lithic graywacke, tuff, conglomerate, limestone, and basalt. Unit includes the Cannery Formation, undivided, defined in Pybus Bay on Admiralty Island by Loney (1964). Graywacke and chert are dominant locally, sericitic cherty argillite is also locally dominant. Graywacke, tuff, and chert are commonly interbedded; grading and rhythmic layering indicates they were deposited as turbidites. Graywacke beds are 2 cm to 5 m in thickness. Graywacke is dominated by volcanic and calcareous rock fragments. Chert contains radiolarians and is intercalated with graywacke, tuff, limestone, and /or volcanic flows. Limestone forms beds up to 50 cm in thickness. Pillow basalt and tuff-breccia form sections up to 100 m thick, and are mapped separately when possible as PDcv. Basalt contains clinopyroxene and plagioclase phenocrysts. Total unit thickness estimated to be greater than 500 m. On Kupreanof Island unit includes 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. Also thin-bedded gray tuffaceous volcanic argillite and fine-grained gray tuffaceous volcanic graywacke; both weather bluish-green or reddish-brown and are intensely fractured; some very thin-bedded dark gray chert, silicified argillite, pillow flows, and gray clastic limestone. The volcanic flows are interlayered with graywacke northwest of Kake and on the northwest shore of Kupreanof Island. On Admiralty Island, the unit includes green mafic to intermediate volcanic and volcaniclastic rocks, with rare metachert on the east side of Pybus Bay. The volcanic rocks are inferred to grade laterally to chert and siliceous clastic rocks. Unit is subdivided into a lower chert member, a middle chert-graywacke member, and an upper argillite-chert member (Karl and others, 2010). In this report, undivided rocks of the Cannery Formation, and the lower chert and middle chert -graywacke members of the Cannery Formation are mapped with PDcc. Where they are sufficiently extensive, the upper argillite-chert member (PDcc) and a mafic volcanic member (PDcv), are mapped separately. A fossiliferous limestone (Ml) is stratigraphically equivalent to the middle chert-graywacke unit and underlies black siliceous slate of the Porcupine Slate (mapped with PDcc) south of the Klehini River. A thick section of black cherty and silty argillite with subordinate pillow basalt and thin limestone lenses between the Klehini and Takhin Rivers west of Haines.
Lithology Sedimentary

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