C URRENT PRE- CA MBRIA N LIT ERA TURE 443 



Mosquito fault — running north of Leadville. They consist of gran- 

 ites, granite-gneisses, mica-schists, and amphibolites, with pegmatite 

 veins traversing them in every direction. Gneisses and schists are the 

 prevailing types. 



A small patch of Cambrian sediment is found resting unconform- 

 ably on the Archean to the east of the Mosquito fault. 



Hague 1 describes the Archean rocks of the area covered by the 

 Absaroka folio in the northwestern part of the state of Wyoming. 

 These consist of crystalline-schists and gneisses, mainly mica-gneiss, 

 amphibolites, and schists distinctly light colored, which are found only 

 in the northeastern part of the Crandall quadrangle. 



Sedimentary rocks of middle Cambrian age overlie the Archean 

 rocks unconformably. 



Irving 2 gives a detailed description of the geology of an area in 

 the northern Black Hills of South Dakota. The Algonkian rocks con- 

 sist of quartzites, slates, phyllites, and schists, all of sedimentary origin. 

 No new point is added concerning the stratigraphy of the pre-Cam- 

 brian rocks. 



C. K. Leith. 



1 Absaroka Folio, Wyoming, by Arnold Hague: Geol. Atlas of the U. S., No. 

 52, 1899. 



2 A Contribution to the Geology of the Northern Black Hills, by John Duer 

 Irving: Annals N. Y. Acad. Sci., Vol. XII, 1899, Pt. 9, pp. 187-340. 



