of
Sample: Sample No. 6AK98 -- USGS No. Mesozoic loc. 3695
Locality: Field No. 6AK98
Description: Canyon entering Billy Creek from the east 2 miles above its mouth. Adolph Knopf, 1906. [description from Martin, 1926, USGS Bull. 776, p. 225]
Location: Alaska Quadrangle: Anchorage
Reference
Title: Report on Referred Fossils ,  1961 (03/30)
Description of the middle Bajocian ammonites from the Cook Inlet region has been completed except for restudy the genus Stephanoceras. I will do that this spring as soon as the photographer is through with the fossils. In the meantime, you may be interested in having a list of the ammonites, of the species of Inoceramus, and in hearing my conclusions concerning the ages of the fossils. The names of the new species should not be listed in your manuscript except for those few that will be published in the May number of the Journal of Paleontology. ........

Many of the other collections from the Tuxedni formation in the Talkeetna Mountains that are listed below correlate with the Gaikema sandstone member or with the Red Glacier member as shown by the presence of Inoceramus lucifer Eichwald. This species at Wide Bay occurs as low as the base of the Kialagvik formation associated with ammonites of early Bajocian age. In the Cook Inlet area it ranges to the top of the Gaikema sandstone member and is associated in the upper part of its range (upper part of Red Glacier member and Gaikema sandstone member) with ammonites of early middle Bajocian age. In the Talkeetna Mountains such ammonites occur at Mes. locs. 3696, 3697, 8585, 24113, 24120, 24134, 24149, 24215, 24420, 25345, 25346, 25942, 25945, and 27577. These ammonites include in particular Sonninia, Witchellia, Papilliceras, Bradfordia, Otoites, Emileia, Labyrinthoceras, Skirroceras, Stephanoceras and Parabigotites. These in association are good evidence for correlating the beds in which they occur with the European zone of Otoites sauzei. Otoites and Labyrinthoceras are characteristic of that zone. Papilliceras, Witchellia and Bradfordia are not known above it. Stephanoceras and Emilea occur rarely below it in the upper part of the zone of Sonninia sowerbyi.

Please note that ammonites mentioned above do include Normannites, Chondroceras (except Mes. loc. 8567), Teloceras and Zemistephanus which are common in the Fitz Creek member of the Tuxedni formation at Cook Inlet. Also, note that the first three of these ammonites are characteristic of the European zone of Stephanoceras humprisianum.

Another item to note is that the Bajocian assemblages in the Talkeetna Mountains doe not include any genera typical of the European zone of Sonninia sowerbyi such as Docidoceras, Eumedtoceras, and Euhoploceras. This zone, likewise, has not been identified along Cook Inlet but is well developed at Wide Bay in the Alaskan Peninsula.

In summary the Bajocian ammonites from the Talkeetna Mountains show that lower, middle, and upper parts of the stage are represented but there is no positive evidence for the presence of beds equivalent to the European zones of Sonninia sowerbyi and Stephanoceras humphriesianum. The fossils from Mes. loc. 8567 could represent the last named zone, or the basal part of the upper Bajocian, or could be a mixture from a considerable thickness of beds, but its ammonite assemblage suggests an age slightly younger than that of the Fitz Creek member.

During the next few months I will be compiling distribution charts and maps and writing several chapters concerning the fossils. As these become available, copies will be sent to you and to Bob Detterman for your use and for criticism.

Report by: Ralph W. Imlay
Referred by: Arthur Grantz
Age: Bajocian (early to early middle Bajocian)
Formation: Tuxedni Group (Tuxedni Formation)
Comment:Many of the other collections from the Tuxedni formation in the Talkeetna Mountains that are listed below correlate with the Gaikema sandstone member or with the Red Glacier member as shown by the presence of Inoceramus lucifer Eichwald. This species at Wide Bay occurs as low as the base of the Kialagvik formation associated with ammonites of early Bajocian age. In the Cook Inlet area it ranges to the top of the Gaikema sandstone member and is associated in the upper part of its range (upper part of Red Glacier member and Gaikema sandstone member) with ammonites of early middle Bajocian age. In the Talkeetna Mountains such ammonites occur at Mes. locs. 3696, 3698, 8585, 24113, 24120, 24134, 24149, 24215, 24420, 25345, 25346, 25942, 25945, and 27577. These ammonites include in particular Sonninia, Witchellia, Papilliceras, Bradfordia, Otoites, Emileia, Labyrinthoceras, Skirroceras, Stephanoceras and Parabigotites. These in association are good evidence for correlating the beds in which they occur with the European zone of Otoites sauzei. Otoites and Labyrinthoceras are characteristic of that zone. Papilliceras, Witchellia and Bradfordia are not known above it.
Occurrence(s)
No. Group Name Qty Notes
1 Bivalves Inoceramus lucifer Eichwald