Reference Detail of

Report on Referred Fossils
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Stratigraphic range: Lower Jurassic
Kinds of fossils: Ammonites
Quadrangle or area: Talkeetna (C-6) and Healy (A-6) quads.
Shipment No.: A-76-33*
Referred by: Detterman, Robert L.
Report prepared by: Imlay, Ralph W.
Date: 02/14/1977

*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.

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F6-S-331 (Mesozoic loc. 31264) , Healy , Divide between Shotgun and Little Shotgun Creeks. 28,800 ft. S. 34 W. from B.M. Copeland, Healy (A-6) Quad., Alaska.
Badouxia canadense (Frebold)
Badouxia columbiae (Frebold)
Arietitid ammonite
F6-S-333 (Mesozoic loc. 31266) , Healy , Crest of ridge on east side of upper Long Creek. 32,700 ft. N. 6 deg. E. from B.M. Copeland, Healy (A-6) Quad., Alaska.
Badouxia canadense (Frebold)
Paracaloceras rursicostatum Frebold
75AR39 (Mesozoic loc. 30908) , Talkeetna , 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 deg. 30'20" N., long. 152 deg. 55'59" W., Talkeetna (C-6) quadrangle, southern Alaska. Unnamed beds. Early Sinemurian. (description from Imlay, 1981, p. 27)]
Coroniceras sp.
32AT1 (Mesozoic loc. 16229) , Healy , Elmer Bedager, 1932. Head of an eastern tributary of Partin Creek that heads agains Little Shotgun Creek on west side of Chulitna River valley north of Eldridge Glacier. Probably same place as USGS Mesozoic loc. 31262 in Healy (A-6) quadrangle, south-central part of Alaska Range, southern Alaska. Unnamed beds. Late early to early middle Sinemurian. (description from Imlay, 1981, p. 26); [ USGS Mesozoic loc. 16229. Head of small eastern tributary of Partin Creek that heads against Little Shotgun Creek north of Eldridge Glacier on west side of Chulitna Valley, eastern Alaska. Arnioceras. (description from Imlay and Detterman, 1973, p. 22)]; [USGS Mes. Cat.: Orig. No. 32AT.1. Head of small eastern tributary of Partin Creek, that heads against Little Shotgun Creek. West side of Chulitna Valley, north of Eldredge Glacier, Alaska. Region Cook In let & tributaries, District Chulitna Valley. Coll. by Elmer Bedager - a prospector and submitted to Ralph Tuck. 19--]
Arnioceras cf. A. densicosta (Quenstedt)
F6-J-27 (Mesozoic loc. 31260) , Healy , Divide between Ohio and Copeland Creeks. 5,800 ft. N. 30 deg. E. of B.M. Copeland in Healy (A-6) quad., Upper Chulitna Districti, Alaska Range, Alaska. [N.J. Silberling and D.L. Jones, 1976. On divide between Ohio and Copeland Creek, 5,800 ft (1,768 m) N. 30 deg. E. of VABM Copeland, Healy (A-6) quadrangle, south-central part of Alaska Range, southern Alaska. Unnamed beds. Late early to early middle Sinemurian (description from Imlay, 1981, p. 26)]
Arnioceras cf. A. densicosta (Quenstedt)
F6-S-322 (Mesozoic loc. 31262) , Healy , Divide between Partin and Little Shotgun Creeks in upper part of small drainage into Partin Creek. 39,850 ft. S. 31.5 deg. W. from B.M. Copeland, Healy (A-6) Quad., Alaska. [N.J. Silberling and D.L. Jones, 1976. Divide between Partin and LIttle Shotgun Creeks in upper part of small drainage into Partin Creek, 39,850 ft (12,147 m) S. 31.5 deg. W. from VABM Copeland, Healy (A-6) quadrangle, south-central part of Alaska Range, southern Alaska. Unnamed calcareous sandstone. Late early to early middle Sinemurian. (description from Imlay, 1981, p. 26-27)]
Arnioceras cf. A. densicosta (Quenstedt)
F6-S-325 (Mesozoic loc. 31263) , Healy , Divide between Shotgun and Ohio Creeks. 19,800 ft. S. 38 deg. W. from B.M. Copeland. Healy (A-6) Quad., Alaska. [N.J. Silberling and D.L. Jones, 1976. Divide between Ohio and Shotgun Creeks, 19,800 ft (6,035 m) S. 38 deg. W. from VABM Copeland, Healy (A-6) quadrangle, south-central part of Alaska Range, southern Alaska. Unnamed beds, Late early to early middle Sinemurian. (description from Imlay, 1981, p. 27)]
Arnioceras cf. A. densicosta (Quenstedt)
F6-S-332 (Mesozoic loc. 31265) , Healy , Divide between Shotgun and Little Shotgun Creeks, 31,700 ft. S. 33 deg. W. from B.M. Copeland, Healy (A-6) Quad., Alaska. [N.J. Silberling and D.L. Jones, 1976. Divide between Shotgun and Little Shotgun Creeks. 31,000 ft (9,449 m) S. 33 deg. W. from VABM Copeland, Healy (A-6) quadrangle, south-central part of Alaska Range, southern Alaska. Unnamed beds. Late early to early middle Sinemurian. (description from Imlay, 1981, p. 27)]
Arnioceras cf. A. densicosta (Quenstedt)