480 DEPARTMENT OF THE INTERIOR 



2 GEORGE V., A. 1912 



strata now to be described.* G. M. Dawson made a traverse up the northeastern 

 headwater of the Skagit river and described the same body of rocks in greater 

 detail.f The area where crossed by Dawson is about fifteen miles north of the 

 Boundary line. Though he measured one section over 4,400 -feet thick and, 

 from paleontological evidence, proved the 'newer Mesozoic ' age of the series of 

 beds — later referring to them as Cretaceous — , Dawson did not give a special 

 name to the series. His brief description will be found to correspond quite 

 closely to the following account of the sediments. The present writer 

 adopts the name 'Pasayten series,' thus modifying somewhat the title given 

 to this great group by Smith and Calkins. The change from the original 

 name, ' Pasayten formation,' seems to make one more appropriate to an extremely 

 thick assemblage of strata which range in age from Lower to Upper Cretaceous. 



Stratigraphy. — On the whole the Pasayten beds are tolerably well exposed, 

 so that the succession can be made out with fair accuracy. ■ At the Porty-ninth 

 Parallel they compose a gigantic monocline with its base at the Pasayten river 

 and its uppermost beds forming the steep ridges north, south, and west of 

 Castle Peak. Across the strike the monocline measures at least sixteen miles 

 in width. West of Castle Peak the youngest exposed member of the series, a 

 thick mass of argillite, is strongly folded and faulted, giving steep dips. The 

 lack of well marked horizons in this folded belt has rendered it as yet impossible 

 to state its exact structure. Consequently there is much uncertainty as to the 

 precise nature of the general columnar section in its upper part. At Lightning 

 creek the argillite is cut off by a profound fault which brings it into sharp, 

 more or less vertical contact with the Paleozoic rocks of the Hozomeen series. 

 In tbe Boundary section, therefore, the top of the Pasayten series is not visible 

 and the youngest exposed bed seems to be truncated by an erosion surface. No 

 other area of the series has been examined in detail and the columnar section 

 can be stated only in terms of observations made in the five-mile belt; such 

 observations are necessarily incomplete. 



As the writer carried his traverses from the basal unconformity at the 

 Pasayten river westward, he became truly embarrassed by the colossal thickness 

 which characterized the successive members. The cumulative thickness in a 

 plainly conformable and comparatively yoting formation seemed almost incre- 

 dible. For this reason special care was exercised in the field to note any possible 

 hints of duplication of strata in the great monocline. It was found, however, 

 that such duplication could have taken place only to a quite limited extent. The 

 upper two-thirds of the series is charged with conspicuous horizon-markers; 

 these would inevitably be repeated visibly among the fine exposures of the rocky 

 ridges, if important duplication through normal faulting or other means had 

 taken place. With a conviction which increased greatly as the field work and 

 then the office study progressed, the writer has concluded that the series must 



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

 p. 14. 



|G. M. Dawson, Report of Progress, Geol. Surv.. Canada, for 1877-8, Part B, p. 105. 



