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Report on Referred Fossils
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Stratigraphic range: Lower Jurassic
Kinds of fossils: Mollusks
Quadrangle or area: Talkeetna B6 and C6 and McGrath B-1 quads., South-central
Shipment No.: A-76-32
Referred by: Reed, Bruce
Report prepared by: Imlay, Ralph W.
Date: 11/09/1976

The fossils at Mesozoic locality 31270 (76AR17) are definitely early Sinemurian as shown by the presence of arietitid ammonites resembling Coroniceras. Locality 31272 (76AR13C) is definitely Early Jurassic as shown by the presence of Weyla. Locality 31267 (76ADt147) contains a species of Gryphaea that resembles G. rockymontana Warren from beds of Sinemurian age in the Fernie Formation of British Columbia and Alberta. The abundance of brachiopods at localities 31267 (76ADt147), 31269 (76AR16A) and 31271 (76AR13B) favors an Early Jurassic age, although brachiopods have been found rather uncommonly in the Middle Jurassic of Alaska. The collections at the remaining localities are too fragmentary for an age determination.

The ariertitid ammonites at locality 31270 (76AR17) greatly resemble those at locality 30908 (75AR39) in the Talkeetna (C-6) quad. The oyster at locality 30907 (75AR38A) that I referred to Ostrea is now assigned to Gryphaea cf. G. rockymontana Warren.

[Note by R.B. Blodgett: the report was dated as 1986, an obvious typing mistake as it was received and stamped by the Alaskan Geol. Br. in Menlo Park on March 15, 1976]

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76ADt147 (Mesozoic loc. 31267) , Talkeetna , Rust weathering limy sandstone in fault contact with Dillinger Group to the west. Elev. 3520 ft., 3.5 miles N. 76 deg. W. from Shellabarger Pass, sec. 1, T. 28 N., R. 20 W., Lat. 62 deg. 32 min. 27 sec. N., long. 152 deg. 52 min. 55 sec. W., Talkeetna (C-6) quad., south-central Alaska.
Ammonite fragment
Entolium? sp.
Gryphaea cf. G. rockymontana Warren
Eopecten? sp.
Rhynchonellid brachiopods
Terebratulid brachiopods
76ADt147A (Mesozoic loc. 31268) , Talkeetna , Black, argillitic, micaceous siltstone. About 30 ft. of black chert that contains 4 to 6 inch beds bearing abundant belemnites. Elev. 3520 ft. 200 yards southeast of loc. 76ADt147. sec. 6, T. 28 N., R. 19 W., Lat. 62 deg. 32 min. 21 sec. N., long. 152 deg. 52 min. 45 sec. W., Talkeetna (C-6) quad., south-central Alaska.
Belemnite fragments
76AR16A (Mesozoic loc. 31269) , Talkeetna , From 10-15 ft. of dark gray medium-bedded, calcareous sandstone that contains many fossils and rests with angular unconformably on the Dillinger Group. Elev. 5890 ft. One mile northwest of the Tatina River. Sec. 25, T. 28 N., R. 20 W., Talkeetna (B-6) quad., south-central Alaska.
Gryphaea sp.
Pleuromya? sp.
Weyla? sp.
Rhynchonellid brachiopods
76AR17 (Mesozoic loc. 31270) , Talkeetna , Same location as 76AR16 but on north side of same ridge. Fossils collected as float from 100-200 ft. of dark gray, fine-grained sandstone. Talkeetna (B-6) Quad.
Arietitid ammonites resembling Coroniceras
Pleuromya sp.
Eopecten? sp.
76AR30B , Talkeetna , Float at Elev. 5500 ft., sec. 11, T. 27 N., R. 20 W., Talkeetna (B-6) quad.
Prismatic calcite suggestive of Inoceramidae
76AR13B (Mesozoic loc. 31271) , Mc Grath , Shell bed in limy sandstone about 15 ft. above angular unconformity. Elev. 4800 ft. to 5200 ft., Sec. 14, T. 26 N., R. 22 W., McGrath (B-1) Quad.
Terebratulid brachiopods
76AR13C (Mesozoic loc. 31272) , Mc Grath , Shell bed in limy sandstone about 25 ft. above unconformity. At same locality as 76AR13B. McGrath (B-1) Quad.
Lima sp.
Weyla sp.
Entolium? sp.
Grammatodon? sp.
76AR13D (Mesozoic loc. 31273) , Mc Grath , Fossils from a 3-6 inch thick limy sandstone bed in a ferruginous sandstone unit at same place as locality 76AR13B.
fragmentary bivalve shells
76AR13E , Mc Grath , A little above 76AR13D
Fragmentary indeterminate shells
76AR15 , Mc Grath , Elev. 4500 ft., Sec. 25, T. 28 N., R. 20 W., McGrath (B-1) quad.
Fragments of prismatic calcite suggestive of Inoceramidae
75AR38A (Mesozoic loc. 30907) , Talkeetna , Brown ferruginous sandstone 150 feet below first Buchia-bearing limestone bed. Elev. 5850 ft. 3.5 miles west of Shellabarger Pass, Central Alaska Range.
Gryphaea cf. G. rockymontana Warren