| Sample: |
Sample No. 71AMk31E -- USGS No. Mesozoic loc. 30137
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| Locality: |
Field No. 71AMk31E
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| Description: |
None given in E&R report. [Imlay, 1981, USGS Prof. Paper 1148, p. 25 provides the following locality description: E.M. MacKevett, Jr. Center of N1/2SW1/4 sec. 8, T. 4 S., R. 11 E., McCarthy (C-7) quadrangle, Wrangell Mountains, southern Alaska. Lower part of upper member of McCarthy Formation. Early Sinemurian.]; [ USGS Mesozoic loc. 30137. Near center of north half of SW1/4 sec. 8, T. 4 S., R. 11 E., in south-central part of McCarthy (C-7) quadrangle. Mesozoic Iocs. 30138-30140 in west half of sec. 17, T. 4 S., R. 12 E., near southeast corner of McCarthy (C-7) quadrangle. Wrangell Mountains, eastern Alaska. All localities are in upper member of McCarthy Formation. Arnioceras (loc. 30140), Megarietites?, and Arnioceras? (loc. 30139), and arietitid ammonites (locs. 30137 and 30138). (description from Imlay and Detterman, 1973, p. 22); [USGS Mes. Cat.: (71AMK-31E) Jurassic, Upper Member of McCarthy Fm. Center of N1/2 of SW1/4 sec. 8, T. 4 S., R. 11 E., McCarthy C-7 quad., Wrangell Mtns, eastern Alaska. Coll. by E.M. MacKevett, 1971] |
| Location: |
Alaska Quadrangle: Mc Carthy C-7 Township&Range: T4S R11E Section: N1/2SW1/4 sec. 8 |
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Reference
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| Title: |
Report on Referred Fossils
,
1971
(11/09)
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The ammonites from the upper member of the McCarthy Formation in the southern part of the McCarthy (C-7) quadrangle are all of Early Jurassic (Sinemurian) age. They represent the same genera as found previously in that member farther east in the Wrangell Mountains. The localities and fossils may be listed as follows: |
| Report by: |
Ralph W. Imlay
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| Referred by: |
E. M. MacKevett
, Jr.
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| | Age: | No Data |
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| Title: |
Jurassic Paleobiogeography of Alaska
,
1973
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ABSTRACT: Jurassic marginal seas occupied considerable areas in southern and northern Alaska and in the western part of the Kuskokwim region of southwestern Alaska. They appear to have been absent during late Callovian time, much restricted during Hettangian, Bathonian, early Oxfordian and late Tithonian time, and most extensive during Sinemurian, Bajocian, and late Oxfordian to middle Tithonian time. A large area in central Alaska was probably never covered. A southwestern prolongation of that area from the Talkeetna Mountains westward to the western end of the Alaska Penin- sula was the site of granitic intrusions during late Early Jurassic time and of extensive erosion during Middle and Late Jurassic time. Variations in the rate of uplift of the area of these granitic intrusive rocks may explain why marine transgressions and regressions were at different times in southern than in northern Alaska during the Bajocian and Bathonian. Connection of the northern and southern marginal seas occurred through Yukon Territory and eastern- most Alaska. The Jurassic ammonite succession in Alaska is similar to that in central and northern Europe and northern Asia. In Lower Jurassic beds, it is essentially identical. In Bajocian and in Oxfordian to lower Kimmeridgian beds, the ammonite succession in Alaska differs from that in the other areas mainly by the presence of some genera found only in areas bordering the Pacific Ocean and by the absence of a few genera common in central and northern Europe. In con- trast, the Bathonian rocks of Alaska contain ammonites, such as Arcticoceras, Arctocephalites, and Cranocephalites, that are widespread in the Arctic region but are unknown in central Europe. Comparisons with the Tithonian of Europe are not possible because ammonites of that age, other than Lytoceras and Phylloceras, are not yet known from Alaska. The Alaskan Jurassic ammonites of late Pliensbachian Age and of Bathonian to early Kimmeridgian Age belong mostly to the Boreal realm and have very little in common with Tethyan realm ammonites such as those found in areas bordering the Mediterranean Sea. |
| Report by: |
Ralph W. Imlay
,
Robert L. Detterman
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| | Age: | Sinemurian |
| Formation: | McCarthy Formation (McCarthy Formation (upper member)) |
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| Comment: | Age: Sinemurian upper member of McCarthy Formation [USGS Mes. Cat.: (71AMK-31E) Jurassic, Upper Member of McCarthy Fm. Generalized location shown as locality 7 in figure 2 |
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