| Sample: |
Sample No. 62AMK53 -- USGS No. Mesozoic loc. 28682
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| Locality: |
Field No. 62AMK53
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| Description: |
R.W. Imlay. 1962. Wrangell Mountains, McCarthy (C-5) quad. Near creek in center SE1/4 NW 1/4 sec. 20, T. 3 S., R. 16E., Nizina Mountain Formation, mostly float. Probably from basal part of the formation. (description from Imlay, 1984, USGS Prof. Paper 1322, p. 30); USGS Mesozoic loc. 28682, in part. Near center SE1/4NW1/4 sec. 20, T. 3 S., R. 16 E., McCarthy C- 5 quadrangle, southern Wrangell Mountains, eastern Alaska (MacKevett, 1963; 1971). Normannites cf. N. variabilis Imlay and Teloceras cf. T. blagdeni (Sowerby) obtained with Cranocephalites, Parareineckeia, and Cobbanites as float derived from a fairly thin sequence. (description from Imlay and Detterman, 1973, p. 24); [USGS Mes. Cat.: 28682. 68AMK-53 (Field Sta. 108). Middle Jurassic. Nizina Mt. Fm. center SENW1/4 sec. 20, T. 3 S., R. 16 E. North of West Fork. McCarthy C-5 quad. Wrangell Mts., Alaska. Coll. by Imlay 1962.] |
| Location: |
Alaska Quadrangle: Mc Carthy C-5 Township&Range: T3S R16E Section: SE1/4NW1/4 Sec. 20 |
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Reference
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| Title: |
Early and Middle Bajocian (Middle Jurassic) ammonites from southern Alaska
,
1984
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| Report by: |
Ralph W. Imlay
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| | Age: | Bajocian (middle Bajocian) |
| Formation: | Nizina Mountain Formation |
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| Comment: | Shown as locality 1 in Figure 2 (fossil locality map). Fossil list taken from Table 2 [p. 26] "In addition, a few ammonites (fig. 2) of middle Bajocian age have been collectioned as float, along with many ammonites of probable early Bathonian age at U.S. Geological Survey Mesozoic locl. 286282... These middle Bajocian ammonites were probably derived from the basal part of the Nizina Mountain Formation, or from underlying beds." [p. 6] "The existence of beds of middle Bajocian age is based on a few ammonites (fig. 8) representing the genera Chondroceras, Normannites, and Teloceras. These ammonites were collected as float at one place near the base of the Nizina Mountain Formation (USGS Mesozoic loc. 28682)." [p. 15] |
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| Title: |
Jurassic Paleobiogeography of Alaska
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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
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Robert L. Detterman
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| | Age: | Bajocian |
| Formation: | Nizina Mountain Formation |
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| Comment: | Age: Bajocian Nizina Mountain Formation Generalized location shown as locality 20 in figure 4 Generalized location shown as locality 20 in figure 4 Normannites cf. N. variabilis Imlay Teloceras cf. T. blagdeni (Sowerby) obtained with Cranocephalites, Parareineckeia, and Cobbanites as float derived from a fairly thin sequence. |
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