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Authors: Marincovich, Louie , Jr.
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Date: /1988
Title: Miocene mollusks from the part of the Bear Lake Formation on Ukonoi Island, Alaska Peninsula, Alaska
, 397 , 1-20 ,
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Document Type: Article\Abst.\Chapter\report
Annotation: 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.

UserNote
77AM22 (Cenozoic loc. M7152) , Port Moller , Shoreline exposure on south shore of Ukolnoi Island, about 120 meters north and 240 meters west of the southeast corner of Section 29, T. 57 S., R. 81 W., Port Moller (A-5) quadrangle; latitude 55 deg. 12.5' N, longitude 161 deg. 35.8' W; Alaska Peninsula, southwestern Alaska. Collected by L. Marincovich, Jr. and H. McLean, 1977: field locality 77AM22; equivalent to LACMIP locality 11011.
Acila sp. indet.
Yoldia sp. indet.
Lucinoma acutilineata (Conrad, 1849)
Macoma sp. indet.
Clinocardium sp.
Pitar? sp.
Mya (Mya) truncata Linnaeus, 1758
Mya sp. indet.
Turritella (Hataiella) sagai Kotaka, 1951
Colus? sp.
Beringius crebicostatus (Dall, 1902)
Dentalium (Rhabdus) cf. D.(R.) schencki Moore, 1964
77AM23 (Cenozoic loc. M7153) , Port Moller , Same general locality as M7152, but about 60 to 120 meters farther to the southwest along sea cliff. Collected by L. Marincovich, Jr., 1977; field locality 77AM23; equivalent to LACMIP locality 11012.
Mytilus (Plicatomytilus) gratacapi Allison and Addicott, 1976
Lucinoma acutilineata (Conrad, 1849)
Macoma sp. indet.
Penitella sp. indet.
Thracia sp. indet.
Turritella (Hataiella) sagai Kotaka, 1951
Neptunea (Neptunea) aff. N.(N.) lyrata altispira Gabb, 1869
Beringius crebicostatus (Dall, 1902)
Tryannoberingius rex Marincovich, 1981
Dentalium (Rhabdus) cf. D.(R.) schencki Moore, 1964
77AM24 (Cenozoic loc. M7154) , Port Moller , Same general locality as M7153, but 60 to 120 meters southwestward along sea cliff. Collected by L. Marincovich, Jr., 1977; field locality 77AM24; equivalent to LACMIP locality 11013.
Lucinoma acutilineata (Conrad, 1849)
Macoma sp. indet.
Pitar? sp.
Thracia sp. indet.
Turritella (Hataiella) sagai Kotaka, 1951
Natica (Cryptonatica) clausa Broderip and Sowerby, 1829
Fusitriton oregonensis (Redfield, 1846)
83ACe87 (Cenozoic loc. M8329) , Port Moller , Sea cliff exposure on unnamed peninsula of the Alaska Peninsula mainland that is east of Balboa Bay, at about 183 meters north and 290 meters west of SE corner of section 4, T. 53 S., R. 73 W., Port Moller (C-2) quadrangle, Alaska Peninsula, southwestern Alaska; latitude 55 deg. 31.65'N, longitude 160 deg. 27.83'W. Collected by J.E. Case, 1983; field locality 83ACe87.
Acila sp. indet.
Mya (Mya) truncata Linnaeus, 1758
Turritella (Hataiella) sagai Kotaka, 1951
83AJm616 (Cenozoic loc. M8331) , Port Moller , [Marincovich 1985:] Specimens from ?Bear Lake Formation at south shore of Ukolnoi Island, Alaska Peninsula. Latitude 55 deg. 12.6' N., Longitude 161 deg. 36.2'. Port Moller A-3 quadrangle.

[Marincovich 1988:] Same general locality as M7152, above. Collected by J.W. Miller, 1983; field locality 83AJm616; equivalent to LACMIP locality 11014.

82AWs39 (Cenozoic loc. M8391) , Port Moller , Along same sea cliff exposure as M8329, above, but 183 meters to the south of M8329; along southern boundary of, and 300 meters west of SE corner of section 4, T. 53 S., R. 73 W., Port Moller (C-2) quadrangle, Alaska Peninsula; latitude 55 deg. 31.60'N, longitude 160 deg. 27.80'W. Collected by F.W. Wilson, 1982; field locality 82AWs39. Specimens collected along exposed coast about 4 km south of San Diego Bay, Alaska Peninsula.
85AYb819 (Cenozoic loc. M8894) , Port Moller , Same locality as M7152, above; collected by R.L. Detterman and M.E. Yount, 1985; field locality 85AYb819.