264 O. 11. Herskey — Belt and J > eIo)ia Series. 



Approximate 

 Name Description . thickness 



in feet 



St. Regis Indurated shales and more or less flaggy sand- 

 stones ; colors mostly green and purple; 

 characterized by shallow-water features. 1,000 



ReVett White quartzites, generally rather thick- 

 bedded ; interstratified with subordinate 

 quantities of micaceous sandstone. 1/200 



Burke Light-gray, flaggy, fine-grained sandstones and 

 shales, mostly greenish, with a variable 

 amount of purple quartzitic sandstone and 

 white quartzite. Shallow-water features 

 throughout. 2,000 



Prichard Mostly argillite, blue-black to blue-gray, gen- 

 erally showing distinct and regular banding. 

 Considerable interbedded gray indurated 

 sandstone, upper portion characterized by 

 numerous alternations of argillaceous and 

 arenaceous layers, and by shallow water . 

 features. Base not exposed. 8,000 + 



17,200 



My study of these rocks has been most extensive in the 

 Wardner District, where I have mapped an area about 4r£ 

 miles long and 3 miles wide. Here the Burke and Revett 

 formations are thicker and more complex than elsewhere in 

 the Coeur d'Alene region and I have found it practicable, in 

 order to bring out the structure better, to make local subdivi- 

 sions of the formations. I have also added another formation 

 at the bottom of the series. This, the Cataldo formation, 

 consists of at least 1,000 feet thickness of heavy beds, many of 

 which are finely laminated and cross-bedded, of medium- 

 grained quartzite of light lilac color, alternating with thinner- 

 bedded strata of dull greenish sericitic quartzite. It is 

 apparently the basal member of the Belt series and probably 

 corresponds to the Creston quartzite of Daly. It does not 

 appear at the surface nor in the mines of the Wardner District, 

 but must underlie them at great depth unless cut out by intru- 

 sive rock. That Calkins did not intend to include it in the 

 Prichard is proved by his mapping a small area of it as Burke. 



The Prichard formation in the Wardner District is largely a 

 dark gray to black argillaceous material in thin regular beds. 

 Where a slaty structure is well developed, the rock resembles 

 the ordinary black slates of other regions. Another type is 

 a hard greenish-gray siliceous shale. Scattered through the 

 formation, but most abundant in the upper part, are beds of 



