Reference
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Title: |
Miocene mollusks from the part of the Bear Lake Formation on Ukonoi Island, Alaska Peninsula, Alaska
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1988
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Abstract: Fossiliferous strata of the Bear Lake Formation crop out on Ukolnoi Island, Alaska Peninsula, southwestern Alaska. The molluscan fauna has an age of 15-16 Ma, or earliest middle Miocene, which is the greatest known age for any Bear Lake outcrop. A similar age is suggested by mollusks for an additional outcrop on an unnamed peninsula to the northeast of Cape Aliaksin on the adjacent Alaska Peninsula mainland. The latter outcrop is the only one known where mollusk-bearing Bear Lake strata are inferred to be in contact with mollusk-bearing strata of the Paleogene Stepovak Formation. The co-occurrence of some molluscan species on Ukonoi Island and at Cape Aliaksin, plus a radiometric age of 10.4 + or - 0.49 Ma for an andesite flow overlying marine strata at the latter site, indicate a middle Miocene age for the Unga Conglomerate Member of the Bear Lake Formation at Cape Aliaksin. The age inforerred from the mollusks at these three localities suggests assignment of these strata to the lower part of the Bear Lake Formation. The Ukolnoi Island molluscan faunule of 18 species lived at depths of about 25 to 35 m in a cool-temperate to subtropical habitat. The presence of some warm-temperate to subtropical Asian taxa suggests that this faunule lived during the peak of the middle Miocene warm interval known throughout the North Pacific region. |
Report by: |
Louie Marincovich
, Jr.
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| Age: | Middle Miocene |
Formation: | Bear Lake Formation |
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