4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 98 



Cambrian strata again constitute the front, and most of the species 

 described in this paper are from Two Mile Canyon, which crosses 

 this outcrop belt. 



In the Bear River Range Middle and Upper Cambrian strata crop 

 out over considerable areas, but their full extent is not known. The 

 best-known section is in Blacksmith Fork Canyon, and another ex- 

 cellent section lies north of Garden City on the eastern slope. Mill 

 Creek west of Liberty, nearly 25 miles north of the Idaho boundary, 

 also exposes a fine Cambrian section. Here the quartzite yields a 

 fauna, and the recently described Spence shale fauna overlies the 

 discontinuous limestone with the Ptarmigania fauna. 



The generalized geological map of northeastern Utah, therefore, 

 shows Cache Valley as a northward-pitching syncline, since it is 

 surrounded by belts of successively older strata from the Car- 

 boniferous to the Cambrian. More detailed mapping does not bear 

 out this structure, but the map does show where Cambrian rocks are 

 found. 



MATERIAL AVAILABLE 



Stratigraphic data. — Measured sections extending through the 

 Middle Cambrian sequence are available at four localities, and partial 

 sections at two other places in the northern Wasatch Mountains. 



In 1898 and 1906 Walcott measured the section in Two Mile 

 Canyon, which is near the northern end of the Wasatch proper. In 

 the same, season he examined the outcrops in Box Elder Canyon, 

 the Mantua Basin, and north of Brigham but recorded measure- 

 ments for only a portion of the sequence. 



During 1906 Walcott, assisted by L. D. Burling, followed up his 

 earlier studies of 1898 in the Bear River Range and measured the 

 sections in Blacksmith Fork east of the southern end of Cache Valley 

 and along Mill Creek west of Liberty, on the eastern slope of the 

 range. In 1909 Blackwelder measured the section on Mill Creek, a 

 tributary entering Blacksmith Fork from the south. This is a few 

 miles south of the place where Walcott worked, but both geologists 

 agree closely in the subdivisions adopted, the lithologic descriptions, 

 and the thicknesses recorded. Recently (1938) Deiss remeasured and 

 republished the Blacksmith Fork section. Walcott recorded 4,190 

 feet of Middle Cambrian beds above the quartzite, Blackwelder 4,125, 

 and Deiss 3,885, which is remarkably close agreement. These ob- 

 servers also recognize the same formational subdivisions with nearly 

 the same respective thicknesses and lithology. 



