| Sample: |
Sample No. 114B of E. de K. Leffingwell, 1911 -- USGS No. Mesozoic loc. 10309
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| Locality: |
Field No. 114B of E. de K. Leffingwell, 1911
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| Description: |
E. de K. Leffngwell, 1911. Sadlerochit River, north side, about a quarter of a mile downstream
from Camp 263 Creek and 1J4 miles upstream from mouth of Neruokpukkoonga Creek about 1,500 feet above base of Kingak shale; lat 69°33' N., long 144°46' W. Middle Jurassic, lower Bajocian. (description from Imlay, 1955, USGS PP 274-D, p. 81); [USGS Mesozoic Catalogue (Washington D.C.) entry: 10309. Orig. no. 114B. Jurassic. 1500 feet above 114A) 10308. Sadlerochit River, Northern Alaska.] |
| Location: |
Alaska No Data
Lat.: 69o33' " Long.: 144o46' " |
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Reference
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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: | Bajocian (early Bajocian) |
| Formation: | Kingak Shale |
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| Comment: | Shown as loc. 33 on Fig. 20 and also on Table 2 |
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