DEVONIAN 289 



significant, and, taken together with the character of the few fossils 

 occurring in it, justifies us in referring the lower 500 feet of the Calico 

 Bhiff section or the portion below the lowest limestone bands to the Devo- 

 nian with considerable assurance. Above number g of the section the 

 beds hold a Carboniferous fauna. 



The above rather fragmentary data clearl}' show both an extensive de- 

 velopment and a wide distribution of rocks assignable to the Devonian in 

 the Upper Yukon basin. If one were to venture on a subdivision of this 

 great series on the facts in hand, it would be to recognize three general 

 groups. The lowest group would comprise the heavy cherty bluish white 

 limestones and associated argillites, quartzites, and thin-bedded lime- 

 stones occurring below Woodchopper creek, which may be Silurian and 

 are characterized by a relatively small anioimt of igneoits material. The 

 cherts, quartzites, and limestones of the Washington Creek area are pro- 

 visionally included with the formation. The lowest member of the Devo- 

 nian or Upper Silurian described by Prindle in the Bampart region, and 

 probably also the rocks of the Stewart river, assigned to the Devonian by 

 Keele, can be provisionally correlated with this general horizon. 



A second group would include limestones and the associated igneous 

 rocks, argillites, and cherts. The igneous rocks of this group would appear 

 to be identical with Spurr's Rampart series; but it must be remembered 

 that it is only for the limestone member of this group that the age has 

 been determined, and that the igneous rocks may be somewhat younger. In 

 its typical occurrence this igneous group is undoubtedly the best defined 

 of the stratigraphic subdivisions here proposed for the Devonian. As a 

 cartographic unit, however, it is not serviceable, because including, as it 

 does, some intrusives, these are likely to be found as dikes cross-cutting 

 various older formations. Moreover, the equivalent of this igneous com- 

 ]ilex in adjacent areas may be found among the purely sedimentary rocks. 

 The stratigraphic relations of Middle Devonian horizon to the older rocks 

 here assigned to the Devonian is not known, but may very likely be one 

 of unconformity. 



The third group includes the argillites and subordinate sandstones and 

 siliceous slates, Avhich occur immediately underneath and conformable to 

 Mississippian terrains. These rocks are but sparingly fossiliferous, and 

 may be found to be in part of synchronous age with the igneous complex 

 of the second group. If the argillite group is distinct from the igneous 

 group, there may be an unconformity between the two, and the apparent 

 absence of the latter in many localities may he due to erosion, which re- 

 moved the igneous rocks before the sediments were laid down. 



Little can be said of the thickness of the Devonian in this province. 



