REPORT OF THE CHIEF ASTRONOMER 505 



SESSIONAL PAPER No. 25a 



in the line of Lightning creek valley and, perhaps simultaneously, along the 

 trough excavated by the Skagit river. In each case the faulting was probably 

 normal, with throws as shown in the profile-section. Less important faults 

 are postulated and mapped at Chuchuwanten creek and in the axis of the anti- 

 cline traversed by the Castle Peak stock. 



CORRELATION. 



The fossiliferous character of the Pasayten series renders possible its 

 definite correlation with the Shasta-Chico series of California. On account of 

 the fact that the youngest members of the series are upturned to verticality 

 and otherwise show evidences of deformation much more intense than that 

 usually seen as a result of Tertiary orogenic movements in the Cordillera, it 

 seems in high degree probable that no Tertiary strata are represented in the 

 series. Impressions of ammonites have, in fact, been found well above tbe base of 

 member L. The upturning of the series is believed to have been largely com- 

 pleted during the post-Laramie orogenic revolution. 



There is no question that the Hozomeen series is in unconformable relation 

 to the overlying Pasayten series. We have concluded that the former series 

 probably represents the Carboniferous Cache Creek series of western British 

 Columbia. 



The pyroclastic beds of the Pasayten volcanic formation bear no fossils but 

 the structural relation of this member to member B of the sedimentary series 

 suggests the advisability of dating the volcanic outburst in the Lower Cretaceous. 

 It is hardly likely that members A and B would show such apparent strict 

 conformity if the volcanics were of Triassic or Jurassic age and a Paleozoic 

 age is almost certainly excluded. If the Remmel granodiorite is truly of late 

 Jurassic age, the Pasayten volcanics cannot be other than post- Jurassic ; among 

 other obvious reasons for this conclusion is the fact that the Pasayten agglo- 

 merate also occurs in pipe-like form within the Eemmel batholith in such 

 relations as to sxiggest strongly a true volcanic neck. • . 



The intrusion of the Castle Peak stock has been assigned to the Miocene. 

 The argument for that reference is much the same as the one outlined for the 

 dating of the Similkameen batholith (page 469). The stock is certainly post- 

 Cretaceous. It shows no sign of such straining as would be expected if it had 

 undergone the squeezing incidental to the late Miocene mountain-building 

 which has so generally affected this part of the Cordillera. The lithological 

 similarity of this stock with the proved Miocene granodiorite of Snoqualmie 

 Pass is some further indication that the stock should be referred to a geological 

 date so relatively recent. 



If the writer is correct in considering the syenite-porphyry chonolith as a 

 satellite from the Castle Peak stock, the chonolith should be dated the same, 

 namely, in the Miocene. 



The Lightning Creek diorite and the apparently satellitic sills and dikes 

 of porphyrite have been subjected to the correlation already briefly discussed. 



