RIVER TERRACES AND GLACIAL SERIES 433 



wide and contains important remnants of the lower terrace. 

 These two lower terraces have dark and light brown debris over 

 the channel gravels proper, but no decided reddish tint. All 

 higher terraces are characterized by a bright red color of the 

 upper dirt layers. 



Channel D seems to be the equivalent of the "lower terrace " 

 or " broad valley floor," described elsewhere from the basins on 

 the lower Klamath and lower Trinity rivers, and Channel E is a 

 local development, scarcely occurring anywhere below Cecilville. 

 •Channel F is mostly buried under the gravel and bowlders of the 

 present river bed. 



At the upper end of the Summerville basin, at the mouth of 

 Rush Creek, there is a very well defined terrace whose surface is 

 at the outer edge about 100 feet above the river. It is well 

 marked along the opposite side of the river as a rather sharp 

 bench. On the north side, facing the river, it has been mined 

 extensively, showing that under its sloping surface there are 

 buried two distinct channels. The outer (Channel C) contained 

 a very bowldery gravel bed from 20 to 30 feet deep, and the inner 

 (Channel B) a similar but thinner and less coarse bed. Most of 

 the bowlders are of the granite of the area on which it rests and 

 from up Rush Creek. A few are of Courtney granite and there 

 are rare small bowlders of serpentine, both from the main valley. 

 The granite bowlders in places are thickly packed. Many are 

 rotten to the center although three feet thick. The red stain in 

 places extends from the surface to a depth of 20 feet. The 

 deposit appears old. It rests on rotten granite. There is a 

 fairly well defined granite platform about 75 feet above the river 

 and a similar platform 30 to 40 feet higher. The sloping surface 

 over these twochannels is the main upper terrace of the Summer- 

 ville basin, but seems to correspond to an intermediate terrace of 

 the systern studied nearer the coast. 



Channel A is represented by a small river deposit occurring 

 at about 250 feet above the river, just below the Summerville 

 buildings. It is much older than any subsequent channel and the 

 space between its level and that of the main upper terrace is 

 characterized in many places by a peculiar rolling topography 



