No. 1.] O. M. DAWSON — GEOLOGY OF PEACE R. REGION. 21 



of the Devonian rocks on the lower Peace, occupy a basin with 

 a width of nearly 350 miles, implying a Cretaceous sea of that 

 width. 



The Rocky Mountains have here formed a shore-line in Creta- 

 ceous times, and the Cretaceous rocks along their eastern base 

 are almost entirely sandstones and conglomerates, the constituent 

 fragments of which can be traced to the cherts and quartzites 

 accompanying the limestones. The mountains are bordered to 

 the east by foot-hills, in which, on the upper part of Pine River, 

 for a distance of fifteen miles from the older rocks, the Creta- 

 ceous sandstones are folded and disturbed. The disturbance, 

 however, gradually diminishes on receding from the mountains, 

 and the beds at length become flat, or are affected by very slight 

 and broad undulations only. Shaly materials increase in im- 

 portance eastward, and the Cretaceous series eventually resolves 

 itself into the following sub-divisions, which are placed opposite 

 their supposed representatives in the Western States : 



Upper, or Wapiti Eiver Sandstones .... Fox Hill (and Laramie ?) 



Upper, or Smoky Eiver Shales Pierre, S 



Lower, or Dunvegan Sandstones Niobrara, v Colorado. 



Lower, or Fort St. John Shales Benton, J 



The correlation as above shown is based partly on palaeontolo- 

 gical evidence, partly on lithological resemblance. The synchro- 

 nism of the upper shales with the Pierre group is quite definitely 

 proved by the fossils. No fossils have been obtained from the 

 overlying sub-division. The fossils of the Lower Sandstones are 

 peculiar, consisting chiefly of fresh-water and estuarine forms 

 and land plants. In the lower shales the most characteristic 

 fossil is a large Ammonite VQS>emh\\ng Ammonites (^Prionocyclus) 

 Woolgari, but according to Mr. Whiteaves specifically distinct. 

 No beds so low as the Dakota horizon have yet been discovered 

 here, though they may exist. 



The lithological resemblance of the shales of the upper and 

 lower sub-divisions to those of the Pierre and Benton groups is 

 exceedingly close. It is conjectured that these mark periods of 

 general submergence, when sediment-bearing currents passed 

 freely through the interior continental valley. In the Dunvegan 

 sandstones we may see an indication of the elevation of land sur- 

 faces to the north and west, which interrupted these currents 

 and allowed the contemporaneous deposition of the Calcareous 

 i^iobTara beds of the South, 



