REPORT OF THE CHIEF ASTRONOMER 509 



SESSIONAL PAPER No. 25a 



the river as about 24,000 feet.* While he did not allow for duplication by 

 fault and fold, his belief that the series is very thick was certainly justified. 

 The Paleozoic section along the Chilliwack river is, indeed, one of the modt 

 complete of all those so far recorded on the western slope of the Skagit range, 

 and besides the definitely Paleozoic strata of this section, there is another 

 important group of Mesozoic beds occurring along the Chilliwack river. To the 

 former group only, and particularly to the Carboniferous portion of it, the 

 name Chilliwack series is intended to apply. Por the first half-dozen miles 

 westward of the Chilliwack batholith there are heavy masses of old-looking 

 sediments which are so far unfossiliferous and may in part belong to the pre- 

 Carboniferous terranes. From the mouth of Slesse creek to a point about ten 

 miles due westward, and from the river southward to the Boundary line, the 

 Chilliwack series is typically represented and is fossiliferous at so many points 

 that little doubt remains as to the Carboniferous age of practically all the 

 sediments occurring in these sixty square miles. 



The eastern limit of the large area of Chilliwack sediments is, within the 

 Boundary belt mapped, fixed by the intrusive contacts of the Slesse diorite 

 and the Chilliwack granodiorite. The western limit is exceedingly difficult 

 to place but is provisionally placed at the outcrop of an assumed master-fault 

 mapped as crossing the belt a few miles west of Tamihy creek. The northern 

 and southern limits of the sedimentary mass have not been determined. 



From the fault just mentioned to another assumed fault running along 

 the axis of Cultus lake valley, the Mesozoic (probably Triassic) formation 

 separates the main body of the Chilliwack rocks from a smaller one which 

 forms much of the long ridge known as Vedder mountain. No fossils have 

 been found in this ridge but it seems most probable that its rocks form the 

 lower part of the Chilliwack series and may be, therefore, all of Carboniferous 

 age. On this view the intervening block of Mesozoic strata have been faulted 

 down into lateral contact with the Carboniferous Chilliwack series. 



Fossiliferous limestones associated with some shale and with a heavy body 

 of contemporaneous andesite make contact with the Mesozoic formation along 

 a line running nearly parallel to, and just south of the Boundary line. The 

 former group represent a part of the Carboniferous series which has, apparently, 

 been here thrust up over the Triassic rocks. The thrust-plane dips south at 

 an unknown angle. 



Finally, the Chilliwack series may be represented in some small areas of 

 poorly exposed quartzites and slaty rocks unconformably underlying the Eocene 

 (?) beds on Sumas mountain. 



Notwithstanding a very considerable amount of arduous climbing distri- 

 buted through part of each season in 1901 and 1906, not sufficient data are in 

 hand to afford a complete idea of the succession of rocks included in the Chilli- 

 wack series. The density of the vegetation in these mountains, unparalleled 

 as it is on the whole Boundary section elsewhere, will always stand in the way 



• H. Bauerman, Eeport of Progress, Geol. Surv. of Canada for 1882-3-4, Part B, 

 p. 32. 



