478 H. J. Biddle — Surface Geology of Southern Oregon. 



An analysis, quoted by Russell,* of a previous sample from 

 this lake showed a remarkably high percentage of potassium 

 salts. The above analysis, on the contrary, shows a less pro- 

 portion of potassium than reported in the waters of Mono 

 Lake, Owen's Lake, or Great Salt Lake.f The writer is at a 

 loss to account for the wide variation between these analyses. 

 Both show a very low percentage of sulphates, far less than in 

 the other lakes of the Great Basin mentioned. 



The occurrence of tufa deposits in the bed of the ancient 

 lake alluded to has not previously been reported. In the low 

 region between the existing water bodies fragments of a calca- 

 reous crust, usually less than one-half inch in thickness, to- 

 gether with concretions of small size, lie sparsely scattered on 

 the surface. Near the shore of Summer Lake the sands are 

 cemented into a crust from one-eighth to one-half inch thick, 

 which appears to be of very recent formation, and might have 

 been formed when the lake stood but a few feet higher than 

 at present. These facts merely go to show that the history of 

 this ancient water body was, in a small way, similar to that of 

 the larger inclosed lakes of the Great Basin. 



Goose Lake Valley is south of the region just described ; it 

 extends nearly north and south, and lies partly in Oregon, 

 partly in California. At its northern end it is connected by a 

 low pass with the southern end of the depression in which 

 Abert Lake lies. This valley was occupied by an ancient lake, 

 the boundaries of which have never been mapped. It had 

 about twice the area of the present Goose Lake, and a depth 

 approaching 300 feet. As the hillsides in this region are in 

 part clothed with forest, the ancient beach lines do not form as 

 noticeable a feature as in the arid valleys north and east of it. 

 Near the town of Lakeview, however, is a conspicuous and 

 well defined terrace, showing the surface level of the ancient 

 lake. This terrace is deeply cut into the spurs of the mountain 

 side, having in places a width of several hundred feet. It has 

 two minor benches, at an elevation respectively of 250 and 

 280 feet above the floor of the valley.^: These benches are in 

 places level, but usually have a lakeward slope of about 5°, 

 and are separated by a somewhat steeper slope. On the side 

 toward the valley the slope increases abruptly, reaching 25°, 

 while toward the mountain there is a gradual increase of slope 

 until the normal inclination of the mountain side is attained. 

 There is no cliff separating the terrace from the mountain 

 slope. The surface of the two benches is often covered with 



*Loc. cit., p. 454. 



+ For a comparison of the analyses of these, and other inclosed lakes, see 

 Monograph XT, C. S. G-. S Geological History of Lake Lahontan, by I. C. Eussell, 

 Table G. 



\ These measurements are by aneroid. 



