CAMBRIAN CORDILLERAN FORMATIONS WALCOTT 9 



of the same relative horizon is called the Flathead sandstone. As 

 the strata are followed to the northwest, the sandy beds occupy a 

 lower stratigraphic horizon until on Gordon Mountain, at the head 

 of the South Fork of the Flathead River, in Montana, the sand- 

 stones are of lower Middle Cambrian age. The Brigham formation 

 should not be confused with the much older Prospect Mountain 

 "quartzite" formation of central Nevada, which is of Lower Cam- 

 brian age. 



Organic Remains. — Annelid trails and trilobite tracks. Charac- 

 teristic Middle Cambrian fossils were found in the upper portion of 

 this formation west of Liberty, Bear Lake County, Idaho. 



HOUSE RANGE, UTAH 



The section exposed in the House Range was first stvidied by Dr. 

 G. K. Gilbert, who made small collections of fossils from various 

 horizons. These collections were so interesting that I visited the 

 range in 1903. In 1905 I revisited the range, in company with 

 Messrs. F. B. Weeks and L. D. Burling, measured the entire section 

 carefully, and made further large collections of fossils. The section 

 extends from well down in the Lower Cambrian to the base of the 

 Ordovician, and is the best and most complete of the Basin Range 

 sections so far studied. A map will be published with the detailed 

 sections, giving the geographic localities referred to in the nomen- 

 clature of the formations of the House Range section. 



The following table gives the relative positions and the thickness 

 of the various formations defined in the following pages : 



Upper Cambrian: ^''eet 



Notcli Peak formation 1,890 



Orr formation 1,825 



Middle Cambrian: 



Weeks formation 1.390 



Marjum formation 1,092 



Wheeler formation 570 



Swasey formation 238 



Dome formation 355 



Howell formation 640 



Lozver Cambrian: 



Pioche formation 125 



Prospect Mountain formation i.200-(- 



NoTCH Peak Formation 



Type Locality.— Upper portion of the main mass of Notch Peak, 

 House Range, Utah. 



