| Sample: |
Sample No. 51ASa56F -- USGS No. Mesozoic loc. 22776
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| Locality: |
Field No. 51ASa56F
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| Description: |
USGS Mesozoic loc. 22776. Easternmost fork of DriftwoodCreek, lat 68°40' N., long 160°26'28" W., northwest Alaska (Imlay, 1955, p. 78, 79). Buchia cf. B. mosquensis (von Buch). (description from Imlay and Detterman, 1973, p. 26); [USGS Mesozoic Catalogue (Washington D.C) entry: 22776. Alaska - 51ASa56f. Kingak - basal(?), sta. no. Sa54 - 68°40' N - 160°26'30" W - west bank of Cirque fork of Driftwood Creek - conglomeratic and conglomeratic shale.]; E.G. Sable, 1951. West bank of easternmost fork of Driftwood Creek at first cutbank above small tributary from the west. Approximate lat 68°40' N., long 160°26'28" W. Conglomerate, conglomeratic shale, and chert, possibly near base of Kingak shale, fossils from concretions in shale. Upper Jurassic, middle Kimmeridgian to lower Portlandian. (description from Imlay, 1955, USGS PP 274-D, p. 78) |
| Location: |
Alaska Quadrangle: Misheguk Mtn C-1
Lat.: 68o40' " Long.: 160o26'28 " |
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Reference
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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: | Kimmeridgian-Tithonian (late Kimmeridgian - early middle Tithonian) |
| Formation: | Kingak Shale (Kingak Shale (basal?)) |
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| Comment: | Generalized locality shown as locality 3 in figure 8 |
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| Title: |
Characteristic Jurassic mollusks from northern Alaska
,
1955
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The fossils from the Jurassic strata of northern Alaska prove that the Lower, Middle, and Upper Jurassic series are represented but suggest that certain stages or parts of stages are not represented. There is no faunal evidence for the presence of the middle and upper parts of the Bajocian, the entire Bathonian, the upper part of the Callovian, the lower Oxfordian, or the upper Portlandian. Field evidence shows that a disconformity occurs at the stratigraphic position of the upper Portlandian. Both field and subsurface data suggest an unconformity immediately preceding the upper Oxfordian. The absence of faunal evidence for certain stages, or parts of stages,may be related to the fact that elsewhere in Alaska and in the western interior of North America major retreats of Jurassic seas occured during Bathonian, late Callovian, and Portlandian times.
Although the Jurassic strata in northern Alaska are generally impoverished faunally, nevertheless, in many places interpretations of the stratigraphy or the structure are based on the fossils present, or the fossils are used as supplementary evidence. Wherever the faunal succession can be determined in northern Alaska, it agrees essentially with that elsewhere in the Boreal region and in other parts of North America and
in northwest Europe.
Faunal and lithologic relationships suggest that the eastward-trending Jurassic seaway of northern Alaska had rather uniform and moderately steep slopes along its northern and
southern margins and that more than half of its sea bottom was stagnant and at least as deep as the lower part of the neritic zone. The existence of moderately deep water may explain the presence of the ammonites Phylloceras, Lytoceras, and Reineckeia, which are missing in the shallow-water Jurassic strata in the interior of North America, in east Greenland, and in the Barents Sea area. The scantiness of the fauna over much of the seaway is problably related to unfavorable bottom conditions and to an inadequate supply of certain materials such as phosphate. Fairly warm waters during Early Jurassic and early Middle Jurassic (Bajocian) time is indicated by the presence of ammonites that had a nearly worldwide distribution. Somewhat cooler waters and the presence of climatic zones
during the Late Jurassic in Alaska, as in other parts of the Boreal region, is indicated by the presence of molluscan genera quite distinct from those in the Late Jurassic of the Mediterranean region. |
| Report by: |
Ralph W. Imlay
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| | Age: | Kimmeridgian-Portlandian (middle Kimmeridgian - early Portlandian) |
| Formation: | Tiglukpuk Formation |
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| Comment: | Shown as loc. 3 on Fig. 20 and also shown on Table 2 The locality description given on p. suggests Kingak Shale, while the entry on Table 2 indicates Tiglukpuk Formation assignment. |
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