Sample: |
Sample No. 53AGz144 -- USGS No. Mesozoic loc. 24821
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Locality: |
Field No. 53AGz144
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Description: |
From upper half of a sandstone unit equivalent to the lower part of the Tuxedni Formation. (description from Imlay E&R report of 3/29/1954; Shipment A-53-25) [Imlay, 1982, p. 12 provides following description: "Arthur Grant and L.F. Fay, 1953. Talkeetna Mountains near head of Sheep Creek, lat 61o 59'17" N., long 147o 38'35" W., Anchorage (D-2) quadrangle. Tuxedni Group, near top in beds equivalent to the Twist Creek Siltstone."]; [24821 Arthur Grantz and L. F. Fay, 1953. Anchorage D-2 quad. on Sheep Creek. Lat. 61° 59' 17" N., Long. 147° 38' 35" W., Tuxedni formation equivalent, upper half. (description from Imlay, 1961, p. 469)]; [USGS Mes. Cat.: 24821. Orig. no. 53AGz-144 - Tuxedni fm. - Middle Jurassic, Nelchina District, Anchorage (D-2), 61°59'17" N., 147°38'35" W., from upper 1/2 of a ss. unit equivalent to the lowerw part of the Tuxedni Fm., on Sheep Creek, Talkeetna Mts., Alaska. Coll. A. Grantz and L. Fay, 1953.] |
Location: |
Alaska Quadrangle: Anchorage D-2 Lat.: 61o59'17 " Long.: 147o38'35 " |
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Reference
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Title: |
Report on Referred Fossils
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1954
(03/29)
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Report by: |
Ralph W. Imlay
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Referred by: |
Arthur Grantz
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| Age: | Middle Jurassic |
Formation: | Tuxedni Group (Tuxedni Formation) |
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Comment: | Collection 53AGz144 contains species of the ammonites Sphaeroceras and Stephanoceras (Polyplectites) that are identical with species in the lower third of the Bowser Member. Inoceramus ambiguus Eichwald occuring in collections 53AGz144 and 139 is also common in the lower third of the Bowser Member, although it ranges from the Fitz Creek Member through the Bowser Member. |
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Title: |
Late Bajocian ammonites from southern Alaska
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1982
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ABSTRACT Early late Bajocian ammonites have been found in southern Alaska in the Talkeetna Mountains, on the west side of Cook Inlet between Tuxedni Bay and Iniskin Bay, and in the lower Kuskokwim-Bristol Bay area north of Togiak Bay. This dating is based mostly only the association of Normannites, Stephanoceras, and Stemmatoceras, which are unknown or rare above beds of that age, with Cadomites and Leptosphinctes, which occur rarely just below beds of that age but range much higher. The dating is also based on the presence of a fragmentary ammonite that in lateral view resembles Spiroceras, a genus not known in beds older than early late Bajocian. Such an association of ammonites occurs west of Cook Inlet in the Twist Creek Siltstone, which rests conformably on the Cynthia Falls Sandstone of late middle Bajocian age and is overlain with marked unconformity by the Bowser Formation of early to late Bathonian Age. Such as association of ammonites is also found in the Talkeetna Mountains in unnamed beds that are nearly identical lithologically with the Twist Creek Siltstone, that rest conformably on beds of late middle Bajocian Age, and that are overlain with probably unconformity by beds of early Bathonian Age. The presence of such an unconformity is suggested by the fact that beds of early late Bajocian age have been found only in two areas in the Talkeetna Mountains, that still younger Bajocian beds have not been found anywhere in southern Alaska, and that still younger lower Bathonian beds are fairly widespread inthe Talkeetna Mountains as well as west of Cook Inlet. Most of the ammonite genera and subgenera present in the Twist Creek Silstone and in equivalent beds in southern Alaska are characteristic of the Tethyan Realm. The exceptions include |
Report by: |
Ralph W. Imlay
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| Age: | Bajocian (early late Bajocian) |
Formation: | Tuxedni Group (Tuxedni Group, near top, in beds equivalent to the Twist Creek Siltstone) |
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Comment: | Beds lithologically and faunally nearly identical with those in the Twist Creek Siltstone west of Cook Inlet have been found inthe Talkeetna Mountains in two areas (figs. 1-3 and tables 2 and 3). One area is near the head of Sheep Creek in the northwestern part of the Anchorage (D-2) quadrangle. The other is 24 to 26 km farther west along the northwest side of Boulder Creek int he Anchorage (D-3) and D-4) quadrangles. The occurrences near Sheep Creek is based on a single collection (USGS Mesozoic loc. 24821) obtained near the top of the Tuxedni Group. The occurrence northwest of Boulder Creek is based on several exposures and on nine fossil collections. (from Imlay, 1982, p. 2) Shown as locality 1 on index map given in Figure 2 |
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Title: |
New genera and subgenera of Jurassic (Bajocian) ammonites from Alaska
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1961
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ABSTRACT-New genera and species of Bajocian ammonites from Alaska include
Megasphaeroceras rotundum Imlay, Dettermanites vigorosus Imlay, and Parabigotites
crassicostatus Imlay. A new subgenus and species is Oppelia (Liroxyites) kellumi
Imlay. Of these Megasphaeroceras, Dettermanites and Oppelia (Liroxyites) are associated
with Spiroceras? Leptosphinctes, and Sphaeroceras of late Bajocian age. Parabigotites is associated with Stephanoceras, Otoites, Sonninia, Witchellia and
Lissoceras of middle Bajocian age. |
Report by: |
Ralph W. Imlay
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| Age: | Bajocian (late Bajocian) |
Formation: | Tuxedni Group (Tuxedni Formation equivalent, upper half) |
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