Kahiltna sedimentary and volcanic assemblage 

(Late Jurassic and Cretaceous) 

(Southern and southwestern Alaska, unit KJs)

Consists chiefly of structurally disrupted, deep marine, partly volcaniclastic, graywacke, argillite, and 
flysch with minor amounts of chert, limestone, conglomerate, and andesite. Mainly Early Cretaceous, but 
includes rocks ranging in age from Late Jurassic to early Late Cretaceous. Metamorphism is mainly lower 
greenschist facies, but ranges from zeolite to amphibolite facies. Occurs mainly along northwest margin of 
Peninsular sequence of Wrangellia superterrane. Interpreted to have originally stratigraphically overlain 
Peninsular sequence on Alaska Peninsula. Thrust over Wrangellia sequence in central Alaska Range. May 
be equivalent to Maclaren Glacier metamorphic belt of the Maclaren terrane in eastern Alaska Range. In 
southwestern Alaska, the Kahiltna assemblage is interpreted to be stratigraphically overlain by Cretaceous 
marine sedimentary rocks of the Kuskokwim Group (unit kw) to north, although the Kahiltna assemblage 
locally contains Late Cretaceous Inoceramus (Turonian). In poorly mapped areas, the Kahiltna assemblage 
seems to grade upward into the Cretaceous Kuskokwim Group. For paleomagnetic determinations, grade A 
data from a series of 66 Ma extrusive volcanic rocks indicate southerly displacements of 14o+6o with 
respect to North America. The Kahiltna assemblage is correlated with the Gravina-Nutzotin-Gambier 
volcanic-sedimentary-plutonic belt to east and southeast. Intensely faulted and folded. Contains fault slices 
of several small terranes, including the Broad Pass, Chulitna, Susitna terranes. Also includes West Fork 
terrane, a sequence of Jurassic chert, argillite, sandstone, volcaniclastic sandstone, and conglomerate, that 
is too small to depict on map. Former Kahiltna terrane of Jones and others (1981, 1987). REFERENCES: 
Reed and Nelson, 1980; Csejtey and others, 1986; Jones and others, 1981, 1987; Thrupp and Coe, 1986; 
Bundtzen and others, 1988; Wallace and others, 1989.