128 ENVIRONMENT OF VERTEBRATE LIFE, ETC. 



lower part. In the upper part these sandstones occur in alternating layers of 

 soft and compact beds full of peculiar black points or specks. These are suc- 

 ceeded by 800 to 900 feet of red shales, with a prominent band of light-colored 

 shale at the top." 



In northwestern Utah the Weber quartzite continues as a strong horizon, 

 but gradually plays out to the northeast of Ogden, Utah. The occurrence 

 of the quartzite is described by Blackwelder:^ 



"At the type locality in Weber Canyon the quartzite is said to be 5000 to, 

 6,000 feet thick, but it thins toward the north and entirely disappears within 8 

 miles, so that farther north the Park City formation is everywhere directly in 

 contact with the Mississippian strata. At the base of the Weber quartzite and 

 intergrading with it, there are red beds consisting of brick-red sandstone with 

 some sandy shale and thin beds of cherty gray limestone. The limestones have 

 yielded a few fossils that are closely related to those in the lower part of the 

 Weber quartzite, and are considered by Girty to be of Pennsylvanian age. The 

 red beds are separated from the underlying limestones by a distinct unconformity, 

 but the testimony of the fossils seems to indicate that the interruption of deposi- 

 tion was brief. The Weber quartzite proper consists of creamy-white quartzite 

 or hard sandstone interbedded, particularly in the lower part, with cherty 

 dolomites of dark gray to black color. A characteristic of the upper beds of the 

 quartzite is a coarse pitting of the surface which is probably due to the leaching 

 out of calcite unevenly distributed through the formation." 



In the Park City district of Utah, adjacent to the area discussed by 

 Blackwelder, the Weber quartzite continues and was described by BoutwelF 

 in 1912: 



"The Weber quartzite, as it outcrops in this region, consists of gray quartzite 

 with comparatively insignificant occurrences of cherty patches and intercalated 

 limestone. It is characterized by massiveness both in bedding, the beds being 

 rarely less than 4 and in many places 8 to 15 feet in thickness, and in the absence 

 of parting planes. On fresh fracture it is a light brownish gray, and it weathers 

 to a glistening surface of a lighter shade. The normal quartzite is fine and even 

 grained and dense. The exceedingly brittle nature of the rock causes it to break 

 into sharp, irregular fragments, and when ground fine in a fracture zone it appears 

 as a glistening white sugary filling inclosing larger fragments. * * * It has been 

 metamorphosed into quartz so completely that the granular form of the original 

 sand is rarely discernible. * * * 



"The middle and basal portions of this formation, which are not present in 

 this area, outcrop in prominent cliffs just south of the district. Except for a few 

 thin limestone beds near its top, the middle portion is massive quartzite, but in 

 the lower part the intercalated limestone members increase in number and thick- 

 ness. In Big Cottonwood Canyon a few limestones are intercalated. A thin 

 crinoidal sandstone occurs about 130 feet from the top, a thin pitted, cavernous, 

 grayish-white quartzite 460 feet below that, and a thinly banded calcareous 



^ Blackwelder, Eliot, Phosphate Deposits East of Ogden, Utah, U. S. Geological Survey, 

 Bull. 430, p. 540, 1909. 



2 Boutwell, J. M., Geology and Ore Deposits of the Park City District, Utah, U. S. Geo- 

 logical Survey, Professional Paper No. 77, p. 45, 1912. 



