hershkv.] The Hire)' Terraces of the Orleans Basin. 



North of Pearch Creek, opposite the fine till exposure at the 

 mouth of the North Fork, there is a small cove between two rock- 

 points. At its head glacial debris extends up the bank to a 

 height of at least 100 feet above the creek, where a bank yields 

 striated boulders. Climbing above this, one finds a mass of 

 broken rock and dirt extending up the valley of the North Fork 

 for several hundred feet. It lacks the granite boulders and 

 other characteristic features of the glacial deposit, but is in the 

 form of a narrow ridge, the crest of which occupies the position 

 of the central line of the old valley of the North Fork. 11 

 appears that the glacier which came down the main valley built 

 its terminal moraine across the valley, exactly at the mouth of 

 the old North Fork Valley. At about the same time a mass of 

 coarse debris came down the North Fork Valley and disposed 

 iself just above the mouth, and partly resting on the north end 

 of the moraine, in the form of a torrent fan. The North Fork 

 Creek was compelled to flow into the depression on the west 

 side of the central ridge, and in consequence has excavated a 

 canon from fifty to seventy-five feet deep, the west wall of 

 which shows bed-rock and the east wall local debris. Before 

 the stream reached the main creek it was turned completely out 

 of the old valley across a rock ridge, over which it now cascades 

 very steeply. 



The glacial deposit probably owes its preservation so near 

 the bottom of the valley to its having been deeply buried under 

 the torrent fan from the North Fork Valley and the landslides 

 which came down the mountain on the south. At first examina- 

 tion the post-glacial erosion at this locality appears less than 

 farther up the creek, but when the overhanging coarse local 

 debris is taken into account, it is evident that as much erosion 

 since the glacialation is here indicated as by the roek canon 

 farther iipstream. 



After repeated visits to this locality and a careful considera- 

 tion of the possibility of this glacial deposit having slidden from 

 some higher position, I have concluded that it is beyond 

 doubt in its original place, and that it is directly the product of 

 ice action. By rough leveling from a point in the Orleans Basin, 

 whose altitude is given on the topographic map of the Orleans 



