| Sample: |
Sample No. 53ADt48 -- USGS No. Mesozoic loc. 24619
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| Locality: |
Field No. 53ADt48
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| Description: |
R.L. Detterman, 1953. Killik Bluffs, 4 miles downstream from junction of Killik River with Okpikruak River. Lat 68o 52' N., long 153o 25' W. Tuktu formation, 700 feet below top. Albian. (description from Imlay, 1961, USGS Prof. Pap. 335, p. 25)[Imlay E&R report of Oct. 15, 1953 (Shipment A-53-14) provides following description: Killik River, Lat. 68o 52' N., Long. 153o 25' W. 800 feet below top of Tuktu.] |
| Location: |
Alaska Quadrangle: Killik River D-1
Lat.: 68o52' " Long.: 153o25' " |
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Reference
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| Title: |
Characteristic Lower Cretaceous megafossils from northern Alaska
,
1961
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Abstract.--The megafossils from the Lower Cretaceous rocks of northern Alaska prove that only the Berriasian, Valanginian, and Albian states are represented by strata. They prove that the lower Berriasian coincides with an erosional unconformity that locally truncates rocks of Jurassic, Triassic, and late Paleozoic age and that Hauterivian, Barremian, and Aptian stages coincide with an angular unconformity involving mountain building, overthrusting, and considerable erosion. They date the Okpikruak formation as being of Berriasian and Valanginian ages and show the earliest Cretaceous sea advanced over a hilly terrane, of which some high spots were not covered until the middle Valanginian. They date the Fortress Mountain formation, the Torok formation, and the overlying formations to the base of the Cenomanian Ninuluk formation as of Albian age only. This is rather astonishing considering that the sedimentary rocks involved, excluding the Fortress Mountain formation, range in thickness from about 9,000 to 11,000 feet. The abrupt termination of the megafossils species at the top of the Albian strata indicates that some major geologic event occurred at the end of Albian time, either in Alaska or in the Boreal region. The Okpikruak formation of Berriasian to Valanginian age in many places contains an abundance of the pelecypod Aucella, but otherwise contains very few fossils. The Aucellas belong to species that are common in the Boreal region and along the west coast of North America. They premit dividing the Okpikruak formation into three faunal zones based on the stratigraphic distibution of the species. The thick shells of the Aucellas and their common occurrence in coarse detrital sedimentary beds suggest that they lived in the shallowest part of the neritic zone or even partly in the littoral zone. The beds of Albian age in northern Alaska include more genera and species of marine megafossils than have ever been described previously from Albian beds in lands bordering the Arctic Ocean. Most of the fossils are from beds that are dated as middle Albian. A scarcity of megafossils in the lower Albian beds coincides with a scarcity of microfossils and is ascribed to exceedingly rapid sedimentation. A scarcity of marine megafossils in the latest Albian beds is explained by the fact that part of these beds are continental and much of the remainder are littoral in origin. The Albian sedimentary rocks are divided on the basis of megafossils into 5 faunal zone, of which 3 are of early Albian age, 1 is of middle Albian age, and 1 is probably of late Albian age. The general composition of the megafossil assemblage living in, or on the bottom of the Albian sea in northern Alaska greatly resembles assemblages living today in shallow sea bottoms of temperate latitudes. |
| Report by: |
Ralph W. Imlay
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| | Age: | Albian |
| Formation: | Tuktu Formation |
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| Comment: | Shown as locality 122 on Plate 21 |
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| Title: |
Report on Referred Fossils
,
1953
(10/15)
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| Report by: |
Ralph W. Imlay
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| Referred by: |
Robert L. Detterman
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| | Age: | Cretaceous (Cretaceous (not further differentiated in this report)) |
| Formation: | Tuktu Formation (Tuktu member of Umiat formation) |
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| Comment: | The fossils from the Tuktu member of the Umiat formation are identical with the species found previously in that member. The most characteristic fossils in your collections are Inoceramus anglicus Woods and Laevidentalium. The pelecypods of Arctica, Entolium, Pecten?, Thracia, Volsella, and Psilomya are probably identifical with species from the Clearwater formation of Alberta, which formation on the basis of ammonites is equivalent to the Torok formation and is slightly older than the Tuktu member. Experience has shown that most species of pelecypods, as we are able to distinguish species among fossils, have longer ranges than most species of ammonites and commonly range through an appreciable part of a stage. Therefore, we might expect to find the same species of pelecypods in the upper part of the Torok formation as in the Tuktu member whenever a similar sandy facies exists. Such a facies would probably be mapped as Tuktu and the fossils would be listed as obtained from the Tuktu. Tuktu member of Umiat formation |
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