Unit symbol: CZogn
Age range Cambrian to Neoproterozoic (635 to 509 Ma)
Lithology: Metamorphic
Group name: Four Winds complex of Gilbert and others (1987), Retreat Group, and orthogneiss
Foliated, lineated, and gneissic biotite-hornblende quartz diorite and granodiorite with minor diorite exposed on southern Prince of Wales, Dall, and northern Admiralty Islands. Most rocks retain recognizable intrusive textures. The more deformed rocks have 5- to 20-cm layers of alternating leucocratic and mafic composition. In most outcrops these compositional layers are thought to be different intrusive phases; in some, however, compositional layering may have resulted from metamorphic segregation (Gehrels, 1991). The False Point Retreat pluton has U/Pb zircon ages of ~545 Ma, 546.9±3.2 Ma, and 544.08±0.84 Ma (S.M. Karl, unpub. data). Elsewhere in southeast Alaska, the Kaigani pluton on Dall Island has U/Pb zircon age of 554±4 Ma (Gehrels, 1990) and orthogneiss at Sunny Cove on Prince of Wales Island has a U/Pb zircon age between 540 Ma and 520 Ma (J.B. Saleeby, unpub. data, cited in Gehrels and others, 1987). Orthogneiss on Bronaugh Islands near Ketchikan has a U/Pb zircon age of 540–510 Ma (Gehrels and others, 1987)

Source map information

Source map Brew, D.A., compiler, 1996, Geologic map of the Craig, Dixon Entrance, and parts of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-2319, 53 p., 1 sheet, scale 1:250,000.
Symbol Cmpw
Unit name Metamorphic rocks on eastern Prince of Wales Island
Description Foliated, slightly layered, metamorphosed diorite, microdiorite, quartz diorite, gabbro, microgabbro, and hornblendite.
Lithology Metamorphic

Correlated geologic units

Label CZog
Description Kaigani, False Point Retreat, and Bronaugh Islands plutons (orthogneiss)
Geologic age Ediacarian
Geologic setting Intrusive, tonalite-granodiorite
Lithology Form Importance
Orthogneiss < Metaigneous < Metamorphic Major