11 New Discoveries in Resolving the Terrane Assembly of Western North American and Northeast Asia (Posters)

Tuesday, 12 May 2015
8:00 AM - 12:00 PM
Atrium/Hallway

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

Paper number: 11-8
Program: Theme Sessions
Time: 8:00 AM – 12:00 PM

Authors

Abstract

We investigated 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, 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).

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: terebratulides referred to Lobothyris; ovate zeilleriides comparable to Cincta; medium-sized biplicate terebratulides; and spiriferinidines referred to Callospiriferina tumida (Von Buch). Sandy and Blodgett (2000) recorded Callospiriferina tumida (Von Buch) from the Talkeetna Formation, Peninsular Terrane, south-central Alaska. Rhynchonellides 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.

We are grateful to Curvin Metzler for making these collections available for study and also to Dr. Cristina Panaiotu for analyzing bivalve shell microstructure. MRS acknowledges the Donors of the American Chemical Society Petroleum Research Fund, for support of this research.