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SILICIFIED ORDOVICIAN BRACHIOPODS 

 FROM EAST-CENTRAL ALASKA 1 



By 

 REUBEN JAMES ROSS, JR. and J. THOMAS DUTRO, JR 



US. Geological Survey, Denver, Colo., Washington, D. C. 



ABSTRACT 



Silicified brachiopods from the Tatonduk River area, central east- 

 ern Alaska along the Canadian border, are possibly of late Middle or 

 early Late Ordovician age. The assemblage closely resembles one 

 described by Schuchert and Cooper (1930) and Cooper and Kindle 

 (1936) from Perce, Quebec, Canada. Many elements are also pres- 

 ent in the classical Caradoc section of Girvan, Scotland. 



Species of Dicoelosia, Ptychopleurella, Cydospira, Ptychoglyptus, 

 Diambonia, and Christiania are very like those from Quebec. Except 

 for Dicoelosia, which has not been reported previously below the 

 Ashgill in Europe, all the above genera plus Catazyga and the species 

 Anoptambonites cf. A. grayae and Xenambonites cf. X. revelatus 

 suggest correlation with rocks of Caradoc age at Girvan. 



The collection is from a thin-bedded shelly limestone unit in the 

 sequence of Paleozoic strata on the north end of Jones Ridge, Charley 

 River (A-l) quadrangle. The locality has special significance because 

 essentially correlative Ordovician strata exposed along the Tatonduk 

 River 7 miles to the southwest are black graptolitic shales. 



INTRODUCTION 



A small collection of silicified Ordovician brachiopods from central 

 eastern Alaska calls attention to a promising area of paleontologic 

 investigation along the Alaskan-Canadian boundary. Although too 

 small in number of specimens to be the basis for definitive conclusions, 



1 Publication authorized by the Director, U.S. Geological Survey. 



SMITHSONIAN MISCELLANEOUS COLLECTIONS, VOL. 149, NO. 7 



