EARLY JURASSIC (PLIENSBACHIAN) BIVALVE AND BRACHIOPOD FAUNA FROM THE PENINSULAR TERRANE, SOUTHERN TALKEETNA MOUNTAINS, ALASKA - PALEOBIOGEOGRAPHIC SIGNATURE AND TECTONIC SIGNIFICANCE

LAZÃR, Iuliana, Department of Geology and Paleontology, University of Bucharest, Nicolai Bãlcescu 1, Bucharest, 010041, Romania, SANDY, Michael R., Geology, University of Dayton, 300 College Park, Dayton, OH 45469-2364 and BLODGETT, Robert B., US Geological Survey - Contractor, 4200 University Drive, Anchorage, AK 99508, michael.sandy@notes.udayton.edu

Here we investigate a North American Jurassic locality with a high diversity brachiopod and bivalve fauna. This Early Jurassic (Pliensbachian) bivalve and brachiopod fauna is from the Talkeetna Formation, Hicks Creek area, southern Talkeetna Mountains, Alaska which is tectonically part of the Peninsular Terrane. As the material has been collected from talus the exact coeval nature of the brachiopods and bivalves has yet to be determined. Ammonites from this locality indicate an early late Pliensbachian age (Kunae Zone); see Caruthers and Smith abstract in this volume.

Eighteen bivalve taxa are identified, representing fifteen genera and subgenera: Parallelodontidae: Grammatodon costulatus (Leanza); Ostreidae: Gryphaea dilobotes Duff, Gryphaea sp.; Neitheidae: Weyla alata (Buch) and Weyla (Lywea) unca (Philippi); Pachycardiidae: ?Trigonodus sp. (probably gen. nov.) and Cardinioides sp. (probably nov. sp.); Kalenteridae: Kalentera sp. (nov. sp.); Trigoniidae: Trigonia (T.) cf. prora Fursich & Heinze, Vaugonia literata (Young & Bird); Family Astartidae: Coelastarte excavata (J. de C. Sowerby); Cardiniidae: Cardinia hybrida (J. Sowerby), Protocardia cf. truncata (J. de C. Sowerby), Protocardia striatula (J. de C. Sowerby); Quenstedtiidae: Quenstedtia sp., Tancrediidae: Tancredia (T.) gibbosa Lycett; Pholadomiidae: Pholadomya sp., Pleuromyidae: Pleuromya uniformis (J. Sowerby).

The brachiopod fauna includes: terebratulids referred to Lobothyris; ovate zeillerids comparable to Cincta; medium-sized biplicate terebratulids; and spiriferids referred to Callospiriferina tumida (Von Buch). Sandy and Blodgett (2000) recorded Callospiriferina tumida (Von Buch) from the Talkeetna Formation, Peninsular Terrane, south-central Alaska. Rhynchonellids have not been recorded from this locality.

The bivalve and brachiopod fauna is consistent with a mid latitude paleogeographic setting for the Peninsular Terrane during the Pliensbachian.

Acknowledgement: Thanks to Curvin Metzler for making these collections available for study and to Dr. Cristina Panaiotu for analyzing bivalve shell microstructure.

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Cordilleran Section Meeting - 105th Annual Meeting (7-9 May 2009)

EARLY JURASSIC (PLIENSBACHIAN) BIVALVE AND BRACHIOPOD FAUNA FROM THE PENINSULAR TERRANE, SOUTHERN TALKEETNA MOUNTAINS, ALASKA - PALEOBIOGEOGRAPHIC SIGNATURE AND TECTONIC SIGNIFICANCE