Consists of graywacke containing “extremely angular, and oscillatory zoned plagioclase, volcanic rock fragments, hornblende, epidote, and calcite grains” (Reed and Nelson, 1980). According to Reed and Nelson (1980), this unit differs significantly from the other sedimentary rocks in the vicinity, which are mapped as part of the Kahiltna assemblage (unit Kfy) flysch. The plagioclase, volcanic rock fragments, hornblende, epidote, and calcite are more abundant in the Yenlo Hills and Reed and Nelson (1980) suggest “that the sandstone may have been derived from the Jurassic magmatic arc (Reed and Lanphere, 1973) now covered by younger rocks in Cook Inlet basin. Contemporaneous volcanism is suggested by rare interbedded light tuffaceous sediments in the Yenlo Hills” (Reed and Nelson, 1980). New detrital zircon analyses indicate a significant peak at 150 Ma, which suggests unit has a maximum age of uppermost Jurassic or is younger in age (Hults and others, 2013)