The single collection from the Naknek formation contains undescribed species of pelecypods that are common in the lower few hundred feet of that formation. Three of the collections from the Chinitna formation contain specimens of the ammonite Cadoceras, which genus has not yet been found in any beds that have been assigned to the Bowser member of the Tuxedni formation.

Collection 58ADt2 contains an undescribed species of Oxycerites that is common in collections obtained from the basal 400 to 600 feet of the Bowser member. It is commonly associated with other ammonites that probably are of late Bajocian rather than of Bathonian age. These ammonites will be studied this next year and a report on them will be sent to you later. Collection 58ADt3 is interesting because it contains a macrocephalitid ammonite, which kind in northwest Europe is known below the upper Bathonian. As this ammonite was obtained only 25 to 50 feet above the lowermost occurrences of Bajocian ammonites (Mes. locs. 2001 and 21318) on Tonnie Creek. The common Inoceramus in the Bowser member appears to me to belong to a long ranging species that first appeared in the Fitz Creek member of the Tuxedni formation and existed until the end of the deposition of the Chinitna formation.

Most of the collections from the Fitz Creek member are near the middle of that member and contain ammonites that in Europe are typical of the upper part of the zone of Otoites sauzei. Collection 58ADt7, however, appears to represent a different level and I suspect that the upper few hundred feet of the Fitz Creek member is equivalent to the European zone of Stephanoceras humphriesianum. This is based partly on a collection (Mes. loc. 20002) made by Wedow 200 feet S. 37 deg. E. of the derrick of the I.B.A. no. 1 well on the right side of Fitz Creek. This collection contains species of Stephanoceras (Polyplectites) and Phylloceras identical with species in the lower part of the Bowser member but it, also, contains a species of Chondroceras similar to a species in the Cynthia Falls sandstone member.

The collections from the Gaikema member contain many undescribed species of pelecypods and the ammonites Normannites and Witchellia. The presence of Inoceramus lucifer Eichwald, judging from previously collecting, indicates a Bajocian age older than that of the Fitz Creek member. The presence of Normannites and Witchellia indicates that the Gaikema member is not much older than the Fitz Creek member. The ammonites at locality 58ADt4 are too poorly preserved to identify positively as Witchellia, but well-preserved specimens of that genus were obtained previously at Mes. loc. 19961 about 180 feet above the base of the Gaikema member. Both Witchellia and Normannites in Europe are known only from the middle Bajocian. Normannites occurs in the zones of Otoites sauzei and Stephanoceras humphriesanum. Witchellia ranges from the zone of Sonninia sowerbyi to the zone of Stephanoceras humphriesanum.

Your collections from the lower siltstone member were meagre, but we have a number of drawers of specimens collected previously. These include such ammonites as Skirroceras, Emileia, Stephanoceras and Sonninia, which furnish a correlation with the European zone of Sonninia sowerbyi.

Collection 58ADt53 from Mash Creek contains impressions of fossils suggesting corals. Helen Duncan sectioned several pieces, but found that organic textures were not visible on the cut surfaces. The only other fossil that has been found on Marsh Creek is a small belemnite fragment (48AMr137) that is of no value in distinguishing between Lower Jurassic and Upper Triassic. The mere presence of corals on Marsh Creek would not be sufficient to distinguish between Lower Jurassic and Triassic unless the corals were sufficiently well-preserve to identify generically. The presence of corals, however, would indicate that the rocks were not younger than Lower Jurassic, considering that corals have not been found in Alaska above the Talkeetna formation.

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Brief statement of problem and remarks (from collector):
Transmitter: Robert L. Detterman
Field stratigraphic assignment: Upper and Middle Jurassic with one sample of L. Jurassic or Triassic.
District or county: Chinitna Bay
Quadrangle: Iniskin-Chinitna Peninsula (Alaska Map 20) 1954
Collector(s) & year(s): R.L. Detterman and D.W. Hinckley-1958