338 INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



The Wellesley formation (conglomerate and slate) of upper Tanana and White 

 rivers is either Carboniferous or Devonian. It is correlated with the Chisna forma- 

 tion of the Copper River district and possibly with the Cantwell formation of the 

 Nenana River section and may represent the base of the Devonian, Ijdng uncon- 

 formably on older rocks. In a recent paper ^°*^ Brooks places the Chisna, Wellesley, 

 and Cantwell in the Carboniferous. 



P 8. YtTKON TERRITORY. 



The Ogilvie Range, which forms the divide between Stewart and Peel rivers, 

 is said by Keele ^^* to consist largely of Devonian strata — ^limestones, ferruginous 

 slates, and quartzites.. These rocks are mapped as altered Paleozoics. CamseU '^^'' 

 collected on Braine Creek, a tributary of Stewart River, and at Braine Pass (latitude 

 64° 30', longitude 135°), at its head, fossils which AVhiteaves identified as Favosites, 

 Productella, and Atrypa reticularis. 



The Braine Pass and section are described as follows :^^* 



Topographically the country between Beaver River [a tributary of the Stewart] and Wind 

 River [a tributary of the Peel] is one of rather rugged rehef. This is the backbone of the great 

 Rocky Mountain system, which here trends northwest and southeast, swinging sMghtly from 

 its almost north and south trend farther south. This particular section is called the Ogilvie 

 Range. Few prominent peaks occur, and from the tops of any of them a general accordance of 

 level can be noticed. The summit of Braine Pass is estimated at about 3,400 feet, and the 

 elevation of the highest peaks in the neighborhood at 6,800. * * * 



A section across the summit from the Beaver River to the Wind shows a series of closely 

 folded and sometimes faulted limestones and slates with some quartzites and conglomerate. 

 Cutting these are some diabase dikes and intrusive rocks. The succession in descending order 

 is somewhat as follows: Massive dovecolored limestone becoming shaly at the base; bands of 

 black slate; massive granular limestone containing fossils; ferruginous slates, weathering red; 

 and black-weathering conglomerate at the base. * * * 



The great valley at the head of Braine Creek, which forms the pass across to the Wind 

 River, is apparently a great line of weakness, which has resulted in [from] an overthrust fault, thus 

 bringing up the underlying ferruginous slates to the surface. 



Some fossil corals and brachiopods collected from the hmestone at the summit and lower 

 down Braine Creek have been identified by Dr. Whiteaves as Devonian forms. 



Q 3. SEWARD PENINSULA. 



In the southeastern part of Seward Peninsula, north of Golofnin Bay, Devonian 

 fossils have been found on Fish River. Somewhat farther northeast,' on the Darby 

 Range, fossils which are regarded as Devonian or possibly Carboniferous have been 

 obtained." 



Q 6-7. YUKON-TANANA REGION. 



The Rampart group, consisting of volcanic rocks with intercalated slates and 

 hmestones, was assigned by Brooks^"^^ on fossU evidence to the Devonian, "probably 

 to the IVIiddle Devonian." In general terms the Devonian of the Yukon-Tanana 

 region may be said to be made up of shales, slates, and cherts, with some limestones; 

 locally ancient lava flows and tuffs predominate over the sediments. On the Yukon 

 the igneous rocks are much more abundant than the sediments; on the Porcupine 

 sediments are most abundant. The thickness of the group is much in doubt but 



<» Smith, P. S., personal commumcation. 



