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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. , Gilbert, Wyatt G.
Report prepared by: Dutro, J. Thomas, Jr.
Date: 08/14/1980

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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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)
echinoderm debris, indet.
fenestrate bryozoans, undet. (includes Polypora, etc.)
orthotetid fragments, indet.
Chonetina? cf. C. superba Gobbet
chonetids, indet.
Rhynchopora? sp.
Spiriferella sp.
Reticularia? sp.
Spiriferellina? sp.
pectenoid fragments, indet.
pelecypod fragments, indet.
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.]
echinoderm debris, indet.
Archeocidaris? sp.
fenestrate bryozoan, indet. (molds & casts)
Polypora spp.
stenoporoid bryozoans, indet. (molds & casts)
Septacamera? sp.
Waagenites? sp.
Chonetinella sp.
chonetids, indet.
Anidanthus sp.
Terrakea? sp.
productoid fragments, indet.
Reticularia? sp.
martinioid, indet.
punctate spiriferoid, indet.
Acanthopecten? sp.
pectenoid pelecypod, indet.
pelecypod fragments, indet.