ORIGIN OF CAMASLAND 221 



cades region has attained such maturity that as yet too few traces of 

 earlier topographic features have been detected upon which to base even 

 conjectures as to the extent to which erosion was carried in preceding 

 cycles. A few deductions from the observed features of Camasland may, 

 however, be made and its history at least partially traced. 



The width of the lower valley of Camas creek has already been men- 

 tioned as seemingly out of all proportion with the present small stream 

 occupying it. This with the width of Camasland itself warrants the 

 inference that it is a valley remnant. The determining factor in the 

 history of this old valley is the diabase sheet, the present extent of 

 which is shown in accompanying plate 20. Its original extent can not 

 be determined, except that the intrusive sheet is not found elsewhere in 

 this area of folded sandstone. 



It may be supposed that the earlier Camas creek, flowing from the 

 south, many miles beyond Camasland, along the general strike of the 

 sandstone, cut down until it suddenly found itself superimposed on this 

 much harder rock. Thus at two points in its course a barrier was en- 

 countered, which became more and more formidable as the cutting pro- 

 ceeded. Two local baselevels were formed, the one on the upper course 

 of the stream and the other above the present outlet of Camasland, the 

 latter the more important and in reality controlling the whole upper 

 portion of the stream. This interruption in the work of general degrada- 

 tion by the upper portion of Camas creek gave the neighboring tributa- 

 ries of Mission creek a decided advantage. The latter stream having 

 less to obstruct its course down to the Wenache river, capture by the 

 Mission drainage was inevitable, as its branches cut their way back to 

 the relatively high valley of Camas creek. The elbow of capture is sit- 

 uated about two miles south of Camasland, where the stream from the 

 south makes an abrupt turn to the east in a canyon 800 feet deep. A 

 portion of Camas creek below this point of capture was obliged to grad- 

 ually reverse its direction of flow until as an obsequent stream it has 

 worked back, capturing another important tributary of Camas creek. 

 Now steep cliffs bound the Camasland plateau on the south, and the 

 divide is established on the diabase rim. 



Before this diversion of the headwaters of Camas creek had been effected 

 the waters flowing across the upper diabase barrier had formed an ex- 

 tensive floodplain at a level established by the lower barrier, and this is 

 the alluvial plain preserved today. This period in the history of Camas- 

 land was of considerable duration, as is shown by the depth and width 

 of the gap cut in the hard diabase at the upper end of Camasland, where 

 the alluvium extends to the very brink of the cliff. It is noticeable that 

 already the obsequent drainage has begun to cut into the diabase sheet, 



