| Description |
Unit includes Cannery Formation, defined in Pybus Bay on Admiralty Island by Loney (1964) where it includes gray, brown, green, maroon, and tan argillite, chert, graywacke, tuff, conglomerate, limestone, and basalt. Graywacke and chert are dominant locally, sericitic cherty argillite is also locally dominant. Graywacke, tuff, and chert are commonly interbedded, deposited as turbidites. Graywacke beds are up to 5 m thick. Graywacke is dominated by volcanic and calcareous rock fragments. Chert contains radiolarians and is intercalated with graywacke, tuff, limestone, or volcanic flows. Limestone occurs in beds up to 50 cm thick. Pillow basalt and tuff-breccia form sections up to 100 m thick. 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. On Admiralty Island, includes Green mafic to intermediate volcanic and volcaniclastic rocks, with rare metachert. Facies to Cannery Formation siliceous sedimentary rocks north of Gambier Bay. In Keku Strait, Halleck Formation volcanic rocks - olivine-rich basalt, pillow flows, pillow breccias, and angular breccias; intercalated with sedimentary rocks of above unit in Saginaw Bay. 5770 (now PDc, Karl and others 2010. I will separate the volcanic rocks of the Halleck Formation = Pv, 5810, out of this unit now.) |
