PLEISTOCENE SUBMERGENCE IN COLUMBIA VALLEY 



497 



A.T. on the slopes of Wood Gulch back of this town. One quartzite, 8 in. 

 in diameter, has glacial striae on one side. These fragments lie below the 

 outcrop of an intra-basalt gravel formation, but quite surely are not derived 

 from it. 



Mottinger, Wash. (4 mi. north of). A distinct mound 4 ft. high and 

 40 ft. in diameter, covered with, and apparently composed of, glacial debris of 

 various kinds, the fragments of various sizes and shapes. It is literally a 

 patch of glacial till deposited on this unglaciated slope. Altitude about 

 1,100 ft. A.T. 



Fig. I. — Erratic near Prosser, Wash. 



Kennewick, Wash. (3I mi. south of). Foreign material very abundant on 

 slopes and summit of the ridge. Summit is 900 ft. A.T. Granite, gneiss, 

 quartzite, vein quartz, slate, porphyritic phanerites and a variety of meta- 

 morphic rock fragments are present. Striated faces are common. In places 

 here the soil looks like the washed surface of a stony glacial till, though the 

 region is many miles from the nearest glaciated area. 



Prosser, Wash, (north of). Slopes below about 1,000 ft. bear many 

 bowlders and fragments of granite and quartzite. The quartzite is prevailingly 

 pinkish to lavender to blue in color, a feature common to most of the angular 

 quartzite in this category. One quartzite is marked with two sets of striae 

 crossing each other. One large granite bowlder, 6X 7X 10, lies at 840 ft. A.T. 

 along the road. It is almost identical in character with the material at 

 Arlington. Riven fragments lying about the bowlder are equal in volume to 

 half the main bowlder (Fig. i). 



Mabton, Wash, (southwest of). Foreign bowlders and cobbles of granite, 

 quartzite, slate, and basalt in considerable numbers lie scattered over the 



