390 INDEX TO THE STEATIGRAPHY OF NORTH AMERICA. 



Feet. 



(c) Green and red sandstones, with brown and black carbonaceous shale, and brown and drab- 

 colored clays. Fossil trees and flora abundant. Coal seams with underclays holding 

 Stigmaria. [Pennsylvanian, "Coal Measures." — David White] 1,000 



{d) Brown and reddish sandstones and conglomerates; brown, blackish, and greenish mica- 

 ceous and arenaceous shale. False bedding in sandstones and ripple-marked surfaces 

 frequent. Fossil plants, among which Sigillaria and Calamites are frequently met with. 

 Thin seams and nests of coal. [Pottsville? — David White] 2,000 



(e) Variegated red, green, and drab-colored marls; red, green, and brown sandstones, which are 

 frequently calcareous; beds of bluish and gray limestones, some beds apparently mag- 

 nesian, and many contain a profusion of organic remains, marine shells, etc., carbonized 

 plants in the arenaceous strata. Salt springs frequent. [Mauch Chunk? — David White]. 2,000 



(5) Great masses of gypsum, with green and brown argillaceous shale; red marly shale; bands 

 of black or dark-gray limestone, and occasionally jet-black shale. [Pocono? — David 

 White] 150 



(a) Very coarse conglomerate composed of great bowlders and pebbles of Laurentian and Silu- 

 rian rocks, cemented in a matrix of greenish-colored sand ; great lenticular intercalations 

 of sandstone with coarse arenaceous shale; large fragments of magnetic iron ore; passes 

 at the top into a brownish-gray flaggy sandstone with brown and greenish shales which 

 underlie the gypsum 1,300 



6,450 

 M-P 8-11. ROCKY MOUNTAINS OF BRITISH COLUMBIA. 



The Cache Creek group of British Columbia is an ill-defined sequence which 

 comprises Carboniferous limestone and various other sedimentary and volcanic 

 rocks. It has been identified more or less surely from the forty-ninth parallel to 

 Alaska in the belt of metamorphic Paleozoic rocks. A comprehensive description 

 is given by Dawson ^'*^' ^^^ in his account of the Kamloops area, in British Columbia, 

 from which the following is condensed : 



The Cache Creek formation, as shown on the present map and as now understood, must 

 therefore be regarded as including a very thick series of Paleozoic rocks, of which the greater 

 part is definitely referable to the Carboniferous period by means of its fossils but of which it is 

 scarcely probable that the upper and lower limits agree precisely with those of the typical 

 Carboniferous. It may very possibly be found at the base, particularly, to transgress these 

 limits and to include beds older than those of the system. 



In attempting a brief general description of this formation, it must in the first place be 

 observed that the extremely broken and disturbed character of the rocks almost everywhere 

 renders it next to impossible to learn much about their attitude or sequence in any one locality. 

 It is very generally impossible to determine whether the dip of the beds is normal or has been 

 overturned. It is thus only by following the general association of the rocks from place to 

 place and by piecing together facts observed at many different places that it becomes practicable 

 to outline the salient features of the whole. 



The western part of the Kamloops sheet, between the Thompson and Bonaparte rivers on 

 one side and the Eraser on the other, is the typical area for the Cache Creek formation, and the 

 most deftaite feature which can be traced throughout is the belt of massive * * * a,nd 

 whitish limestones, sometimes marbles. * * * 



Practically the entire mass of the Marble Mountain Range is composed of these limestones, 

 as well as the whole eastern part of the Pavilion Mountains. They include comparatively 

 insignificant intercalations of argillite, cherty quartzite, and materials of volcanic origin. 

 Farther south, in the region to the east of Hat Creek, such materials become more abundant 

 and form thick beds among the limestones, particularly the cherty quartzites and the green- 

 stones. In this region it is probable that the lower part of the great limestone series is most 

 prominently displayed and that the higher beds are more characteristic in the north, particu- 

 larly in the Marble and Pavilion mountains. The earlier stages of the great period of limestone 

 deposition appear to have been marked by frequent interruptions, during which argillaceous 



