G. M. Dawson — Geology of British Columbia. 221 



many times repeated. East of the lower part of the Fraser Kiver 

 the fok^s have been completely overturned to the eastward. 



These rocks of the Coast Kange have with other features of the 

 country a great extension in a north-east and south-east bearing, 

 stretching, with an average width of 100 miles at least, from the 

 49th parallel to Alaska, a distance of 500 or 600 miles. 



Pre- Cretaceous Bocks of the Interior. — North-east of the Coast 

 Eange the older rocks of the interior plateau are more varied, but 

 have in their different developments characters in common with each 

 other and with those of the Coast Eange, which draw them closely 

 together. These rocks, which were included under the Lower and 

 Upper Cache Creek groups of the original classification, may be said 

 as a whole, in their present state, to consist of massive limestones, 

 diorites or allied materials, felspathic rocks, compact agglomeritic 

 or slaty quartzites and serpentines. The last-named rock occurs in 

 association with the contemporaneous volcanic materials, and doubt- 

 less represents the alteration product of olivine rocks. It is in beds 

 of considerable thickness and wide-spread, and is of interest as being 

 of a period so recent as the Carboniferous. The limestones are not 

 unfrequently converted to coarse-grained marbles, and together with 

 the quartzite appear in greatest force on the south-western side of 

 the area they occupy. They have now been traced, maintaining their 

 character pretty uniformly throughout, fi'om the 49th to the 53rd 

 parallel. Schistose, or slaty argillite rocks, which may represent 

 those already described as folded with the Coast Eange series, also 

 occur, and a portion of these at least probably belongs to the over- 

 lying Triassic or Jurassic division. 



In regard to the evidence of the age of the great mass of these 

 rocks, forming the so-called Upper and Lower Cache Creek groups, 

 the following points may be mentioned. A portion at least of the 

 formation was in 1871 shown, by fossils collected by Mr. Selwyn, to 

 belong to a horizon between the base of the Devonian and summit of 

 the Permian. Additional fossils have since been procured, of which 

 the most characteristic is the peculiarly Carboniferous foraminifer 

 Fusulina. This has now been found in several localities, scattered 

 over a wide area, and is associated at Marble Canon with the remark- 

 able Loftusia Columbiana.^ 



In the southern portion at least of the interior plateau region there 

 exist, besides the Palseozoic rocks just described, and in addition to 

 the probably in part Triassic argillites, extensive but as yet undefined 

 ai'eas of Triassic rocks of another character. These are in great part 

 of volcanic origin, and have been designated the Nicola series. They 

 have generally a characteristically green colour, but are occasionally 

 purplish, and consist chiefly of felspathic rocks and diorites, the 

 latter often more or less decomposed. The rocks are in some cases 

 quite evidently amygdaloidal or fragmental, and hold toward the 

 base beds of grey sub-crystalline limestone, intermingled in some 

 places with volcanic material, and containing occasional layers of 

 water-rounded detritus. The distinctly unconformable junction of this 

 1 Quart. Joxirn. Geol. Soc, 1879, p. 69. 



