Angayucham terrane 

(subduction zone - predominantly oceanic rocks) 

(East- and West-Central, Alaska, and Brooks Range)

Exposed in elongate belts and large klippen. Divided into lower (Slate Creek), middle (Narvak), and upper 
(Kanuti) thrust panels.

Lower (Slate Creek) thrust panel—Consists chiefly of phyllonite, melange, and sedimentary broken 
formation. Sedimentary part consists mainly of thin-bedded, quartz, and chert-rich graywacke turbidite 
deposits of continental derivation, chert, phyllite, and slate. Contains local tectonic blocks of volcanic 
rocks, chert, limestone turbidite, chert-pebble conglomerate, and shallow-marine clastic deposits. Contains 
palynomorphs, conodonts, radiolarians, brachiopods and plant fragments ranging in age from Devonian to 
Early Jurassic. Locally to pervasively deformed and metamorphosed to lower greenschist facies in the 
Mesozoic, particularly along northern margin where phyllonite is common. Slate Creek thrust panel 
includes both Prospect Creek, Slate Creek, and Venetie terranes of Grantz and others (1991) and Moore 
and others (1992); interpreted as a tectonic unit that separates the structurally underlying, regionally 
metamorphosed and deformed rocks of Coldfoot, Endicott, Hammond Mountains, and Ruby terranes from 
overthrust oceanic rocks of Narvak thrust panel. REFERENCES: Jones and others, 1987; Murphy and 
Patton, 1988; Moore and Mull, 1989; Moore and Murphy, 1989; Dover, 1990; Grantz and others, 1991; 
Patton, 1992a, b; Moore and others, 1992; Patton and others, 1992, 1994

Middle (Narvak) thrust panel—Consists chiefly of structurally interleaved diabase, pillow basalt, tuff, 
chert, graywacke, argillite, minor limestone, and volcanogenic sandstone, conglomerate, and tuff. Locally 
abundant gabbro and diabase. Cherts range in age from Late Devonian to Early Jurassic. Limestone is 
mainly Carboniferous. Devonian corals, brachiopods, and graptolites from shale and limestone beds in 
extreme east-central Alaska. Interpreted as major accumulations of late Carboniferous and Late Triassic 
basaltic volcanism; however, many volcanic sequences are not yet well dated. Basalt interpreted as oceanic 
island or plateau basalt based on associated sedimentary facies and trace-element discriminate patterns. 
Includes Tozitna, Innoko, and Woodchopper Canyon terranes of Jones and others (1981, 1987) and Grantz 
and others (1991), and Rampart Group of east-central Alaska.

Narvak thrust panel structurally and stratigraphically complex; generally highly faulted and locally folded. 
Metamorphosed to greenschist facies and locally blueschist facies at base of thrust panel. Narvak and Slate 
Creek thrust panels structurally overlie the Coldfoot terrane to north and Ruby terrane to south; and are 
structurally overlain by Kanuti thrust panel and Koyukuk terrane. Locally in southwestern Alaska, protolith 
forms stratigraphic basement to Koyukuk terrane. Narvak thrust panel depositionally overlain by 
Cretaceous clastic deposits of Yukon-Koyukuk Basin, and by Late Cretaceous and early Tertiary Yukon-
Kanuti and Kuskokwim Mountains igneous belts. Narvak thrust panel interpreted as a subduction-zone 
complex composed chiefly of oceanic crust and seamounts. Locally in southwestern Alaska, Narvak thrust 
panel may be stratigraphically overlain by rocks of Koyukuk terrane. REFERENCES: Brosgé and others, 
1969; Murchey and Harris, 1985; Barker and others, 1988; Jones and others, 1988; Pallister and Carlson, 
1988; Pallister and others, 1989; Patton and others, 1977, 1992, 1994; Patton, 1992a, b

Upper (Kanuti) thrust panel—Consists chiefly of serpentinized pyroxenite, harzburgite, dunite, wehrlite, 
cumulate gabbro, non-cumulate gabbro, and diabase. Basal contact of ophiolite locally marked by 
amphibolite metamorphosed at the time of structural emplacement in the Middle Jurassic (Boak and others, 
1987). Includes Misheguk Mountain terrane of Grantz and others (1991) and other isolated klippen of 
ultramafic and mafic rocks that structurally overlie the Narvak thrust panel. Kanuti thrust panel interpreted 
as the basal part of an ophiolitic assemblage emplaced during Middle or Late Jurassic onto an apparently 
unrelated middle (Narvak) thrust panel of basalt. Kanuti thrust panel interpreted as the root of an island arc, 
possibly the tectonically suprajacent Koyukuk terrane. REFERENCES: Patton and others, 1977, 1992, 
1994; Wirth and others, 1986; Boak and others, 1987; Loney and Himmelberg, 1985, 1989; Mayfield and 
others, 1988; Karl, 1992; Patton, 1992a, b.