of
Sample: Sample No. 61-ABC-27 -- USGS No. Mesozoic loc. 28577
Locality: Field No. 61-ABC-27
Description: Latitude 61o 36'15"; Longitude 142o 37'40". From limy interbeds in shale section ca 250' above Weyla-bearing ls. (description from transmittal sheets of D.L. Jones); M. C. Blake, 1961. On ridge just south of a rock glacier in SE1/4 SE1/4 sec. 14, T. 3 S., R. 15 E., lat 61°36'15" N., long 142°37'10" W., McCarthy (C-5) Quadrangle, Wrangell Mountains, southern Alaska. Root Glacier Formation, about 76 m above the top of the Nizina Mountain Formation. Early Kimmeridgian. (description from Imlay, 1981, USGS PP 1190, p. 24); [USGS Mesozoic Catalogue: (61ABC-27). Upper Jurassic. McCarthy C-5 Quad. Alaska. Lat. 61°36'15"; Long. 142°37'40". From limy interbeds in shale section. About 250' above Weyla-bearing limestone. Coll. by M.C. Blake - 7-61.]
Location: Alaska Quadrangle: Mc Carthy C-5
Lat.: 61o36'15 " Long.: 142o37'10 "
Reference
Title: Report on Referred Fossils ,  1961 (11/09)
The Jurassic beds in the McCarthy area of the Chitina Valley represents at least the lower part of the Lower Jurassic, the Bathonian or basal part of the Callovian stages, and the upper Oxfordian and Kimmeridgian stages.

The Lower Jurassic fossils are in general rather poorly preserved. Many of the identifications are querried and hence have little value in determining the exact age within the Lower Jurassic. Thus collections F-3A and F-45 contain ammonites resembling Wahneroceras which, if correctly identified, are good evidence for a Hettangian age. However, the specimens do not show certain critical features necessary for the identication of the genus.

In contrast the Sinemurian stage of the Lower Jurassic is represented by Arnioceras (locs. F-4 and F-35) which in northwest Europe ranges through the lower and midle parts of the stage. The ammonites Crucilobiceras (Loc. F-1) and Microderoceras (Mes. loc. 14472) could be either uppermost Sinemurian or lower Pliensbachian. In addition the pelecypod "Entolium" semiplicatum (Hyatt) is probably indicative of a Sinemurian age as it occurs in abundance with ammonites of that age in eastern Oregon and locally in the Sierra Nevada (Sailors Canyon Formation).

The Weyla-bearing limestone has furnished no fossils of age value other than Weyla itself, which genus is known only from the Lower Jurassic. I understand that Si Muller has examined the Weylas from the McCarthy area and identified some of them with a species that occurs in Nevada and Oregon in beds of late Pliensbachian to Toarcian age.

Most of the collections from the Jurassic shale above the Weyla-bearing limestone contain species of Buchia of late Oxfordian and Kimmeridgian age. These include Buchia concentrica (Sowerby) (locs. F-17, F-19, F-34, F-50, 61-ABC-26, Mes. loc. 14495 and 14496), B. rugosa (Fischer) at many localities, and B. mosquensis (von Buch) at a few localities. Of these species, B. concentrica (Sowerby) is of late Oxfordian to early Kimmeridgian age (see Prof. Paper 314-G, p. 159, 165). Near the top of its range elsewhere in Alaska it is associated with B. rugosa (Fischer) and less commonly with B. mosquensis (von Buch), both of which range higher into beds of probably Portlandian age. The ammonite Prionodoceras (locs. 61-ABC-27, 61-ABC-36, 14495, 14496 and 14497) in the Boreal region is of late Oxfordian to early Kimmeridgian age and is commonly associated with Buchia concentrica (Sowerby). I suspect that it was collected lower than B. rugosa (Fischer), but I would be much interested in knowing your conclusions concerning the stratigraphic positions and ranges of these fossils in the McCarthy area.

Three of the collections (locs. 61-60, F-28, 61-ABC19) from the shale above the Weyla-bearing limestone are of considerable interest because they contain genera of ammonites that have been found in the Cook Inlet area in the middle part of the Bowser member of the Tuxedni formation and in the lower part of the Chinitna formation. In my paper dealing with the Callovian ammonites from Alaska (Prof. Paper 249-B) I referred the ammonites in question to Procerites? (pl. 54) and Reineckeia (pl. 55). As your collections do not contain any of the ammonites, such as Cadoceras and Kepplerites, that are common in the Chinitna formation, I suspect that the collections represent older beds equivalent to some part of the Bowser member. In any case their age is either Bathonian, or early Callovian and they are distinctly older than the beds containing Buchia.

We still lack descriptions of localities F-6, F-50 and 61-19. When these arrive, Mesozoic numbers will be assigned to the collections and a list sent to you. Also, sometime we would like to have a quadrangle map, or maps, showing the exact occurrences of the fossil localities. Any stratigraphic information that you can furnish relating to the localities to the tops or bottoms of formation, or to marker beds, will be nice to have in our record books.

Report by: Ralph W. Imlay
Referred by: David L. Jones , E. M. MacKevett , Jr.
Age: Oxfordian-Kimmeridgian (late Oxfordian - early Kimmeridgian)
Comment:Cited in E&R report as being from "New localities in Jurassic shale above the Weyla-bearing limestone."

The ammonite Prionodoceras (locs. 61-ABC-27, 61-ABC-36, 14495, 14496 and 14497) in the Boreal region is of late Oxfordian to early Kimmeridgian age and is commonly associated with Buchia concentrica (Sowerby). I suspect that it was collected lower than B rugosa (Fischer), but I would be much interested in knowing your conclusions concerning the stratigraphic positions and ranges of these fossils in the McCarthy area.

Occurrence(s)
No. Group Name Qty Notes
1 Ammonoids Amoeboceras (Prionodoceras) sp.

Title: Late Jurassic Ammonites from Alaska ,  1981
Report by: Ralph W. Imlay
Age: Kimmeridgian (early Kimmeridgian)
Formation: Root Glacier Formation
Comment:Shown as loc.. 5 on Fig. 1; also shown on Figure 3 and Table 4

The exact stratigraphic positions of most of these ammonite fossil localities (table 4) in relation to the base of the Root Glacier Formation is not determinable because of faulting and folding. Nonetheless, Mesozoic loc. 28577 is about 250 feet (76 m) above the base; Mesozoic locs. 14495, 14496, 14497, and 28578 are probably 1,000 to 2,000 feet (303 to 606 m) above the base; and Mesozoic loc. 28579 is about 1,500 feet (454 m) above the base. Within the McCarthy (C-5) Quadrangle, the lowermost part of the Root Glacier Formation is dated as late Kimmeridgian by the association of Amoeboceras (Amoebites?) with Buchia concentrica (Sowerby) at USGS Mesozoic loc. 28577 (from Imlay, 1981, p. 16)

Occurrence(s)
No. Group Name Qty Notes
1 Bivalves Buchia concentrica (Sowerby)
2 Ammonoids Amoeboceras (Amoebites?) sp. specimen from this locality illustrated in Pl. 12, fig. 2