264 A. H. BROOKS — RECONNAISSANCES IN SOUTHEASTERN ALASKA 



only of minor importance, as is shown by the very gentle folding found 

 in the Tertiary beds. So far as known, there is absolutely no evidence 

 of a southern extension of the post-Tertiary disturbance which Russell* 

 noted in Saint Elias regions. The most recent evidences of dynamic 

 activity are the volcanic rocks of mount Edgecumbe and some basalt 

 flows which have been found in various parts of the province. 



One of the effects of the crustal movements is to produce lines of weak- 

 ness in the rocks which have been sought out by the erosive agencies. 

 These structural lines, which are shear zones and lines of foliation, have 

 affected not only the bedded but also the massive rocks, and consist of 

 two systems, the one having nearly a north and south trend, the other 

 running northwest and southeast. The position of the channels and 

 inlets of this coastal belt is largely determined by these structural lines 

 (compare map, page 257). 



CORBEL A TION 



The stratigraphy of the regions lying adjacent to the province under 

 discussion is too imperfectly known to enable correlations to be made. 

 It will be of interest, however, to draw attention to certain analogies of 

 stratigraphic succession and lithologic character in adjacent regions. 

 This is especially true of the field to the south, where the Canadians 

 have done some more or less detailed mapping. 



In a previous report f the writer grouped the Carboniferous and Devo- 

 nian beds of the upper White and Tanana rivers together under the 

 name Nutzotin series. This Nutzotin series would in a measure corre- 

 spond to the subdivision called Upper Paleozoic on the accompanying 

 map, but will probably also embrace a part, at least, of the argillites 

 which lie adjacent to the Coast range. In the report cited the limestones 

 of Glacier bay were all put in the Nutzotin series, as they were then be- 

 lieved to be Carboniferous. In the same report the pre-Devonian sedi- 

 ments are grouped together as the Kotlo series, which would include the 

 rocks of the Lower Paleozoic, as defined in this report. As in south- 

 eastern Alaska, the two series are separated by an unconformity, and 

 there are, broadly speaking, certain lithologic similarities. 



In the Copper River district Schrader % and Spencer have described 

 two formations which probably fall in the Upper Paleozoic. These are 

 the Chitistone limestones, believed to be Carboniferous, and the under- 

 lying Nicolai greenstone. This limestone can be provisionally correlated 



*Nat. Geog. Mag., vol. iii, 1891-92, p. 1(17. 



f A reconnaissance from Pyramid Harbor to Eagle City. Twenty-first Ann. Rept. U. S. Geol^ 

 Survey, part ii, p. 359. 

 \ Geology and mineral resources of the Copper River district. U. S. Geol. Survey, 1901. 



