Report on Referred Fossils |
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Stratigraphic range: |
Lower Permian |
Kinds of fossils: |
Brachiopods, bryozoans |
Quadrangle or area: |
McGrath A-5 |
Shipment No.: |
O-80-45 |
Referred by: |
Blodgett, Robert B.
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Gilbert, Wyatt G.
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Report prepared by: |
Dutro, J. Thomas, Jr.
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Date: |
08/14/1980 |
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This report covers 2 collections made by Wyatt Gilbert in the McGrath A-5 quadrangle, west-central Alaska. Both collections are from fine-grained clastic rocks with abundant fenestrate bryozoans, brachiopods, and a few pelecypods. The brachiopods are definitely Permian in age and the association with a variety of bryozoans, including POLYPORA, is characteristic of some parts of the lower Permian sequences elsewhere in the Alaska (for example, the east-central Alaska Range in the lower argillite member of the Eagle Creek Formation, and the Rampart Group of the Tanana-Livengood area). There are differences between the brachiopod assemblages in these two collections. Collection 77WG203, including the large CHONETINA?, RHYNCHOPORA? AND SPIRIFERELLA sp. may be a bit younger than the other, although differences may reflect environmental factors. In any case, they both appear to be Lower Permian.
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User Note module to be added |
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77WG203
, Mc Grath
, Alaska, McGrath A-5 quad.; precise locality not given. Collector: W. Gilbert, 1977. (description from Dutro E&R report of 8/14/80)
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echinoderm debris, indet.
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fenestrate bryozoans, undet. (includes Polypora, etc.)
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orthotetid fragments, indet.
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Chonetina? cf. C. superba Gobbet
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pectenoid fragments, indet.
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pelecypod fragments, indet.
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79WG113
, Mc Grath
, Rocks at this locality are siliceous-cemented mudstone which is exposed as talus rubble. Locality coordinates: Lat. 62 deg. 05.4'N, Long. 155 deg. 11.3' W; NW1/4 NE1/4 NW1/4, sec. 17, T23N, R32W, McGrath A-5 quadrangle, 1:63,360 scale, 1954 edition. From interbedded fine-grained, siliceous-cemented, clastic rocks and limestones that form the uppermost beds within an unnamed argillite and chert unit, whose total thick probably exceeds 600 m (approx. 2,000 ft). Abundant bryozoans, brachiopods and pelecypods are also found at the same locality. (description from Hahn et al., 1985). [Dutro E&R report of 8/14/80 provides following description: Alaska, McGrath A-5 quad.; NW 1/4 NE 1/4 NW 1/4 sec. 17, T. 23 N., R. 32 W.; silicified limestone lens within uppermost part of unnamed chert-argillite unit. Collector: W. Gilbert, 1979.]
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echinoderm debris, indet.
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fenestrate bryozoan, indet. (molds & casts)
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stenoporoid bryozoans, indet. (molds & casts)
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productoid fragments, indet.
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punctate spiriferoid, indet.
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pectenoid pelecypod, indet.
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pelecypod fragments, indet.
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