Alaska Paleontological Database

Sample Detail

of

Sample:	Sample No. 75AR39 -- USGS No. Mesozoic loc. 30908
Locality:	Field No. 75AR39
Description:	Brown siltstone and sandstone, ferruginous. Elev. 6100 ft. 5 miles southwest of Shellabarger Pass, Central Alaska Range. [D.L. Jones, 1975. Altitude 6,100 ft (1,859 m), 5 miles (8 km) southwest of Shellabarger Pass, lat 62^o 30'20" N., long. 152^o 55'59" W., Talkeetna (C-6) quadrangle, southern Alaska. Unnamed beds. Early Sinemurian. (description from Imlay, 1981, p. 27)]
Location:	Alaska Quadrangle: Talkeetna C-6 Lat.: 62^o30^'20 ^" Long.: 152^o55^'59 ^"

Reference

Title:	Report on Referred Fossils , 1975 (10/03)
	The fossils from localities 75AR38A and 39 are definitely Lower Jurassic as shown by the presence of arietitid ammonites and the pelecypod Weyla. Also, the presence of Coroniceras at locality 75AR39 shows that the beds at that place are definitely lower Sinemurian. The fossils from locality 75AR38C include belemnites preserved in a brown sandstone matrix and Buchia crassicollis solida preserved in a limestone matrix. Apparently the fossils from two different beds got mixed just as they did last year (locs. 74ARA68B and C). Please ask Dave Jones to check the fossils from locality 75AR38B for possible mixing. The ammonites from Mesozoic loc. 16229 near Partin Creek (see description in Prof. Paper 801, p. 22) were collected by Elmer Bedager, a prospector, and submitted to the Survey geologist Ralph Tuck in Alaska during the field season of 1932. The general area was described by S. R. Capps in 1919 (USGS Bull. 692, p. 207-232). Locality 16229 is in the Healy (A6) 15 min. quad., a copy of which will be sent to Dave Jones for field use in 1976. The collection contains about 15 specimens of undeformed ammonites that show the features of Arnioceras very well. In addition it contains one fairly smooth, evolute ammonite suggestive of some member of the Juraphyllitidae, one undeformed Pleuromya and several fragments of Pectinids. Evidently the Jurassic at that place is not metamorphosed or deformed.
Report by:	Ralph W. Imlay
Referred by:	Bruce Reed


Age:	Sinemurian






Comment:	The fossils from localities 75AR38A and 39 are definitely Lower Jurassic as shown by the presence of arietitid ammonites and the pelecypod Weyla. Also, the presence of Coroniceras at locality 75AR39 shows that the beds at that place are definitely lower Sinemurian.

Occurrence(s)
No.	Group		Name	Qty	Notes
1	Ammonoids		Coroniceras sp.
2	Belemnites		Belemnites
3	Bivalves		Ostrea
4	Bivalves		Plagiostoma
5	Bivalves		Plicatula?
6	Bivalves		Oxytoma cf. O. cygnipes Phillips
7	Bivalves		Entolium

Title:	Report on Referred Fossils , 1977 (02/14)
	Revised report. Identifications of Lower Jurassic ammonites from the Alaska Range have been revised slightly. The species at localities 31264 and 31266 that previously were assigned (A-76-33) to Psiloceras? canadenseFrebold are now assigned to a newly described genus Badouxia* Guex and Taylor (1976, La limite Hettangian-Sinemurian, des Prealpes romandes au Nevada: Ecologae Geol. Helvetiae, v. 69, no. 2, p. 525). These authors present evidence (p. 521-526) that some ammonites associated with the new genus Badouxia in British Columbia (Frebold, 1967, Geol. Survey Canada Bull. 158) belong the genera Vermiceras, Paracaloceras, and Charmasseiceras which are characteristic of the early Sinemurian in Eurasia, Indonesia and Nevada and are not known from the Hettangian. This knowledge is useful in dating certain beds at Puale Bay, Alaska, where such genera as Paracaloceras and Badouxia have been found about 650 ft. below the base of the Kialagvik Formation (Mes. locs. 10820, 12396 (part) and ROC 1240 and ROC 1241). In the Healy (A-6) quadrangle the presence of Arnioceras at Mesozoic locs. 16229, 31260, 31262, 31263, 31265 is good evidence of a somewhat younger early Sinemurian age, although the genus in Europe ranges from the upper part of the Arietites bucklandi zone into the Asteroceras obtusum zone. The youngest Jurassic fossils found to dae in the Healy (A-6) quadrangle consist of Arctoasteroceras jeletzkyi Frebold in association with Paltechioceras (Orthoechioceras?) at Mesozoic locality 31261. Of these taxa, A. jeletzkyi was dated by Frebold (1960, Geol. Survey Canada Bull. 59, p. 26, table 1) as middle late Sinemurian because of its association with Oxynoticeras oxynotum. Its association with Paltechioceras at loc. 31261 is good evidence, however, of a latest Sinemurian age corresponding to the European zone of Echioceras raricostatum. It is possible, of course, that Arctoasteroceras ranges from the oxynotum into the raricostatum zone. As a result of these revisions the ammonites found in the south central part of the Alaska Range are now listed as follows: Badouxia canadense (Frebold) 31264, 31266 Badouxia columbiae (Frebold) 31264 Coroniceras sp. 30908 Arnioceras cf. A. densicosta (Quenstedt) 16229, 31260, 31262, 31263, 31265 Arietitid ammonite 30907, 31264, 31270 Paracaloceras rursicostatum Frebold 31266 Arctoasteroceras jeletzkyi Frebold 31261 Paltechioceras (Orthechioceras?) sp. 31261. Any comments or corrections that you want to make will be appreciated.
Report by:	Ralph W. Imlay
Referred by:	Robert L. Detterman


Age:	Sinemurian (early Sinemurian)






Comment:	Early Sinemurian (age given in locality descriptions given after faunal list on p. 2 of E&R report)

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