| Sample: |
Sample No. 78AM8 -- USGS No. Cenozoic loc. M7327
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| Locality: |
Field No. 78AM8
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| Description: |
Type section of Bear Lake Formation, on southwest side of ridge about 2 miles east of Bear Lake, section 4, T. 49 S., R. 70 W., Port Moller (D-1) quadrangle; lat. 56o, 58 min. N., long. 160o, 07 min., W. This locality is the same as M1186 (upper horizon) given in Burk (1965, Geol. Soc. America Memoir 99). Locality M7327 is about 250 feet below top of stratigraphic section. |
| Location: |
Alaska Quadrangle: Port Moller D-1 Township&Range: T49S R70W Section: Sec.4
Lat.: 55o58' " Long.: 160o07' " |
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Reference
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| Title: |
Report on Referred Fossils
,
1980
(03/18)
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This report deals with six collections of megafossils from the Bear Lake Formation on the Alaska Peninsula, southwestern Alaska, and it relates to Branch of Alaskan Geology AMRAP project 9310-01381. This report complements one I did on Bear Lake mollusks from R.L. Detterman on 12/20/78. Collections below made by Louie Marincovich. |
| Report by: |
Louie Marincovich
, Jr.
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| Referred by: |
Robert L. Detterman
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| | Age: | Middle Miocene-Late Miocene (late middle Miocene - early late Miocene) |
| Formation: | Bear Lake Formation |
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| Comment: | Age: The mollusks are referable to the Wishkahan Stage of the molluscan chronology developed for Tertiary faunas of Washington and Oregon, and are assigned an age of late middle or early late Miocene. Two bivalves, Felaniella parilis and Acila empirensis, are known only in Wishkahan and younger faunas. Of the tentatively identified bivalves, Spisula albaria is known only in Wishkahan and older faunas, and Siliqua oregonia is reported from Wishkahan and possibly older faunas. The gastropod Neptunea lyrata altispira has reliable records in late Miocene and Pliocene faunas and may also occur in middle Miocene strata. Several of the mollusks in this collection occur also in the type section of the Tachilni Formation at Cape Tachilni, the fauna of which is also assigned to the Wishkahan Stage.
Environment: The mollusks lived in shallow, temperate water, probably very near to the shoreline. The modern bathymetric ranges of several bivalves, including Mya (0-50 m.), Mytilus (0-45 m.), Felaniella (0-75 m.), Siliqua (0-60 m.) and Chione (0-45 m.), suggest a very shallow site of deposition. Carbonized plant fragments, usually less than 5 mm. in greatest dimension, are extremely abundant at these two localities and are strong evidence for a near shore depositional site. The bivalve Spisula often has its highest abundance in sandy embayments, and the fine plant debris may also have required a somewhat protected environment in order to settle to the sea bottom. A large proportion of the bivalve specimens in these collections are articulated and closed, and nearly all specimens of Mya were observed at the outcrop in life orientation --- this very strongly suggests that the molluscan fauna largely or entirely represents a life assemblage rather than an assemblage transported to this stie by currents or wave action. |
| Occurrence(s) |
| No. |
Group |
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Name |
Qty |
Notes |
| 1 |
Bivalves |
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Spisula (Mactromeris) cf. S. (M.) albaria (Conrad, 1848) |
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abundant |
| 2 |
Bivalves |
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Siliqua cf. S. oregonia Dall, 1909 |
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| 3 |
Bivalves |
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Hiatella arctica (Linnaeus, 1767) |
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| 4 |
Bivalves |
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Macoma (Macoma) optiva Yokoyama, 1923 |
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common |
| 5 |
Bivalves |
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Macoma (Macoma) aff. M. (M.) astori Dall, 1909 |
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common |
| 6 |
Bivalves |
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Macoma incongrua (von Martens, 1865) |
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| 7 |
Bivalves |
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Macoma sp. |
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| 8 |
Bivalves |
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Tellina (Peronidia) protovenulosa Nomura, 1935 |
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| 9 |
Bivalves |
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Chione (Securella) ensifera (Dall, 1909) |
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| 10 |
Bivalves |
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Chione (Securella) cf. C. (S.) ensifera (Dall, 1909) |
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| 11 |
Bivalves |
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Acila (Truncacila) empirensis Howe, 1922 |
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| 12 |
Bivalves |
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Acila (Truncacila) sp. |
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| 13 |
Bivalves |
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Clinocardium cf. C. brooksi (Clark, 1932) |
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abundant |
| 14 |
Bivalves |
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or Clinocardium ciliatum (Fabricius) |
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abundant |
| 15 |
Bivalves |
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Felaniella parilis (Conrad, 1848) |
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| 16 |
Bivalves |
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Nuculana cf. N. pernula (Mueller, 1779) |
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| 17 |
Bivalves |
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Nuculana sp. |
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| 18 |
Bivalves |
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?Mytilus (Plicatomytilus) gratacapi Allison and Addicott, 1976 |
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| 19 |
Snails |
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?Buccinum sp. |
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| 20 |
Snails |
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Polinices (Euspira) pallidus (Broderip and Sowerby, 1829) |
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| 21 |
Snails |
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Natica (Cryptonatica) clausa Broderip and Sowerby, 1829 |
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| 22 |
Snails |
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Natica (Tectonatica) janthostoma Deshayes, 1839 |
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| 23 |
Snails |
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Margarites (Pupillaria) sp. |
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| 24 |
Snails |
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Neptunea (Neptunea) lyrata altispira Gabb, 1869 |
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| 25 |
Snails |
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?Neptunea sp. |
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| 26 |
Snails |
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?Mohnia sp. |
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| 27 |
Snails |
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Colus sp. |
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| 28 |
Snails |
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Crepidula cf. C. rostralis Dall, 1909 |
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| 29 |
Snails |
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Crepidula princeps Conrad, 1856 |
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| 30 |
Echinoids |
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sand dollar echinoids |
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fragments abundant |
| 31 |
Annelida |
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worm (?) tubes |
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fragments rare |
| 32 |
Plants |
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carbonized plant fragments |
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abundant |
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