THE SPENCE SHALE AND ITS FAUNA 



By CHARLES ELMER RESSER 



Curator, Dizision of Stratigraphic Paleontology, 



U. S. National Museum 



(With Six Plates) 

 INTRODUCTION 



The Spence shale occurs in the northern Wasatch Mountains, in 

 northeastern Utah and adjacent portions of Idaho. Thus far neither 

 this shale nor its fauna has been found south of Brigham, but it is 

 present in both the Wasatch proper and its eastern prong, the Bear 

 River Range. Fossils are everywhere present, sometimes in great 

 abundance and variety. 



In 1896 R. S. Spence sent some very interesting and well-preserved 

 Middle Cambrian fossils to Dr. Charles D. Walcott. Correspondence 

 shows that additional material was sent during the next 10 years. 

 Late in the summer of 1906 Dr. Walcott moved camp from Black- 

 smith Fork to the eastern slopes of the Bear River Range in the 

 vicinity of the locality discovered by Mr. Spence. A brief description 

 of the sections studied in 1906, together with formational names, 

 was published by Walcott in April 1908 (1908a). In December of 

 the same year (1908b) the sections were republished in more detail, 

 including preliminary faunal lists. Unfortunately, the several sec- 

 tions measured in both divisions of the Wasatch were combined into 

 a composite section, thereby obscuring essential stratigraphic facts. 



The Spence shale was defined (Walcott 1908a) as "argillaceous 

 shales" about 30 feet thick with "an extremely abundant and varied 

 lower Middle Cambrian fauna," and in the fuller description (Wal- 

 cott 1908b) the words "and sandy shale" were added. This thin 

 stratigraphic unit was regarded as a member at the base of the Ute 

 formation. It is not a mappable unit and therefore deserves recog- 

 nition only for its abundant and striking fauna. 



The type locality for the Spence shale is in Spence Gulch, which 

 is situated on the eastern slopes of the Bear River Range, about 

 5 miles southwest of Liberty and 15 miles west of Montpelier, Idaho. 

 Similar beds, but with few fossils, are recognized to the south near 

 Garden City. On the western slope of the Bear River Range, the 



Smithsonian Miscellaneous Collections, Vol. 97, No. 12. 



