284 BEOOKS AKD KINDLE PALEOZOIC ROCKS OF UPPER YUKON 



be referable to the Middle Devonian, as pointed out in the discussion of 

 the Porcaipine fauna (see page 328). Unless, therefore, the Devonian 

 section begins earlier on the Yukon than on the Porcupine, of which 

 there is no positive evidence, the limestones near Woodchopper lie near 

 the base of the Devonian section. Their Middle Devonian age is sug- 

 gestive of an unconformity at their base. 



"\Miile this evidence points to the Middle Devonian age of the lime- 

 stones associated with the greenstones, the greenstones may be somewhat 

 younger, and represent about the same horizon as the Upper Devonian 

 shales and slates to be described as occurring between Eagle and Calico 

 bluff. If this proves to be the case, it would indicate that while igneous 

 activity was widely spread, yet the resulting extravasations were compara- 

 tively local. 



It is worthy of note that rocks of a similar diabasic composition have 

 been described by McConnell" as occurring along the Yukon near Daw- 

 son and called by him the "Moose Hide group." McConnell shows that 

 this rock is greatly sheared and in part altered to serpentine. The obser- 

 vations of the writers indicate that this same terrain forms the greater 

 part of the country rock along the Yukon from Dawson to the mouth of 

 Fortymile river. 



Spurr's t}'pe locality for the igneous rocks included in the Eampart 

 series is along the Yukon below the Flats in the so-called Eamparts. 

 Though this area was not studied in detail bj^ the writers, yet the same 

 t^'pes of rocks are loiown to occur as those described on the upper river. 

 Unfortunately there have been no fossils found in the Eamparts of the 

 Yukon and the correlations depend on the general lithologic similarity. 



MendenhalP® has described an igneous complex under the name Kanuts 

 series, which occupies an area of several hundred square miles between the 

 Eamparts of the Yukon -and the KoATilvuk valley. This complex is made 

 of basic igneous rocks, including both effusive and extrusive, together 

 with some pyroclastics and hornstones. ]\Iendenhall points out the simi- 

 larity of these rocks to Spurr's Eampart series and provisionally assigns 

 them to the Middle Paleozoic. 



In the region south of the Eamparts there are many greenstones'^ in 

 association with various t}q3es of sediments which have been assigned to 

 the Devonian. These greenstones are of diabasic character and include 



" R. G. McConneU : The Klondike gold fields. Geological Survey of Canada, no. 884, 

 1904, pp. 22B-23B. 



"5 Walter G. Mendenhall : A reconnaissance from Fort Hamlin to Kotzebue sound. 

 Professional paper no. 10. V. S. Geological Survey, pp. 32-38. 



™ L. M. Prindle and Frank L. Hess : Tlie Rampart gold placer region. BuUetin no. 

 280, U. S. Geological Survey. 



