The collections from localities 75ARR 205 G, H and I on the Niguanak River are dated as late Early Bajocian by the presence of Pseudolioceras whiteavesi (White) and Erycitoides howelli (White) which in southern Alaska occur directly below ammonite faunas charatertistic of the European Sonninia sowerbyi Zone (Westermann, 1969, Bull. Am. Paleontology, v. 57, no. 255, p. 345-352, fig. 5) and with ammonite genera not known above the European Graphoceras concavum Zone (Wetermann, 1969, fig. 8 on p. 18). Canavarella in England has been recorded from the European zone of Tmetoceras scissum near the base of the Middle Jurassic.
The collection from locality 75ARR 209 on the Aichilik River is dated as late Bethonian by the presence of Arcticoceras. That genus on Ignek Mesa in northern Alaska and in East Greenland (Callomon, 1959, p. 505-512, table) occurs at the top of a Bathonian ammonite succession consisting from the base upward of Cranocephalites, Arctocephalites and Arcticoceras. In east greenland it is succeeded by the earliest occurrences of Paracodoceras and Kepplerites which are succeeded in turn by ammonites of earliest Callovian age as in northwest Europe.