Volcanic rocks of Chugach accretionary complex

Unit symbol: Kafv
Age range Upper Cretaceous (83.6 to 66 Ma)
Lithology: Sedimentary
Group name: Chugach accretionary complex
Tholeiitic metabasalt; massive greenstone; and basaltic metatuff, including local pillow lava, pillow breccia, and gabbroic dikes and sills (Winkler and Plafker, 1993) typically interbedded with flysch of the Valdez Group (unit Kaf) and Sitka Graywacke (unit Ksg). Metabasalt forms rugged, nearly massive outcrops, whereas semischistose metatuff forms more subdued outcrops (Winkler and Plafker, 1993). Dated by association with the sedimentary part of the Valdez Group. Metamorphic grade ranges from prehnite-pumpellyite to lower greenschist facies (Winkler and Plafker, 1993). Basalt and basaltic tuff north of Cross Sound are deformed and regionally metamorphosed as high as amphibolite facies (Gehrels and Berg, 1992, Dusel-Bacon and others, 1996b). Common rock types include schist, gneiss, and amphibolite (Brew and others, 1978). Correlation with volcanic rocks in Valdez Group to northwest suggests a Cretaceous age (Brew and Morrell, 1979a; Plafker and Campbell, 1979)

Source map information

Source map Plafker, George, 2002, Unpublished data.
Symbol Kpm
Unit name Pelitic and quartzofeldspathic schist and gneiss
Description Pelitic and quartzofeldspathic schist and gneiss with abundant sills, dikes, and small intrusive bodies of felsic granitic rocks (2715 on WRST map)
Lithology Metamorphic

Correlated geologic units

Label Kvsg
Description Valdez Group -- Schistose to gneissic metaflysch and migmatite
Geologic age Late-Cretaceous
Geologic setting Metamorphic, undivided
Lithology Form Importance
Gneiss < Metamorphic Amphibolite Indeterminate, major
Migmatite < Metamorphic Amphibolite Indeterminate, major
Schist < Metamorphic Amphibolite Indeterminate, major