A Lower Permian fusulinid fauna was found in rocks of Mankomen age within a fault block in the Upper Delta River area, east-central Alaska Range. Three members of the M ankomen Formation are recognized and described from this area. They are, in stratigraphic order: a lower Tuffaceous Sandstone Member, an Alternating Limestone-Shale Member, and a Limestone Member. Additional sedimentary rocks occur still higher in the section but are as yet unmapped. The section exposed in this area represents the youngest known Upper Paleozoic sediments in the Alaska Range.

Eighteen species of fusulinids belonging to three genera are described from the Alternating Limestone-Shale Member and Limestone Member. They are: Pseudofusulinella valkenburghae n. sp.; P. cf. P. parvula Skinner and Wilde; P. sp. A; Eoparafusulina mendenhalli n. sp.; E. waddelli n. sp.; Schwagerina pseudokaragasensis n. sp.; S. cf. S. emaciata (Beede); S. sp. A; S. rowetti n. sp.; S. callosa (Rauser-Chernousova); S. whartoni n. sp.; S. heineri n. sp.; S. moffiti n. sp.; S. sp. B; S. sp. C; S. rainyensis n. sp.; S. mankomenensis n. sp.; and S. hyperborea (Salter). This fauna is divided into six assemblage zones on the basis of the fusulinid species. Collectively, the zones indicate a Lower Permian age, ranging from late Asselian to middle Artinskian when compared to the zonation of Permian sections in the western Urals, USSR.

The fusulinids from the Lower Permian of the Alaska Range belong to the Boreal faunal realm that includes the geosynclinal seas of the Alaskan Cordilleran, Franklinian, and Uralian geosynclines. Faunal evidence indicates temporary marine connections between Alaska and the Pacific north-west, and between the Uralian and Tethyan regions.

Correlations are suggested between the Alaska Range section and the following regions: southeastern Alaska; northeastern Alaska; northwestern Yukon Territory; Grinnell Peninsula, Arctic Archipelago; northwest Greenland; Spitsbergen; and the Ural region of the USSR.