18 FIELD OPERATIONS OF THE BUREAU OF SOILS, 1910. 



West of the Sacranieiito River and in a very few places on the east 

 side, it consists of sand, chiy, and waterworn gravel. The pebbles in 

 the gravel are usually small, well rounded, and derived from fine- 

 grained eruptive rocks, quartz and quartzite, etc. The pebbles when 

 exposed are usually weathered to a reddish color, or are mixed with 

 and coated with the finer material, which is reddish in color. In 

 general, on the east side of the valley the ancient deposit consists 

 mainly of waterworn gravel with a relatively small proportion of 

 sand and a still smaller proportion of clay. The pebbles are much 

 larger, as a rule, than those on the west side, are well rounded, and 

 derived from basaltic rocks. The sands are likewise mainly basaltic 

 in origin. Avith small quantities of quartz, and in addition, there are 

 occasional layers of basaltic tuff. 



The soils derived from the ancient deposits of the western side of 

 the valley are classed under the head of the Redding, Corning, and 

 in part, as the Tehama series. 



In tlie Redding series two types were mapped. They are prevail- 

 ingly reddish in color and usually carry quantities of waterworn 

 gravel. These types occupy the highest elevations in their section of 

 the survey and are gently sloping to rolling in contour. They possess 

 thin layers of heavy subsoil resting directly upon a true, impenetrable 

 hardpan several inches thick. This hardpan in turn is underlain by 

 indefinite masses of coarse deposits in a partially cemented condition. 

 Most of this series is poorly adapted to dry-farming methods, is bar- 

 ren in appearance, and locallv known as " red lands '' or " hardpan 

 lands." 



In the southwestern part of the Red Bluff area occur several bod- 

 ies at about the same relative elevation as the Redding series farther 

 north in the area. These ridges and small elevations in this section 

 are occupied by remnants of the Red Bluff' formation, but in an 

 altered state sufficient to remove them from the Redding series. Tiie 

 true hardpan seems to have been removed, and there are somewhat 

 deeper coverings of soil resting upon the semicemented deeper lay- 

 ers. This material constitutes the Corning series with two type 

 subdivisions. As with the Redding, it is a distinctly west-side series, 

 and poorly adapted to dry farming. 



The Tehama series occupies two topographic situations and is de- 

 rived from two different materials, so far as origin is concerned. 

 All of the Tehama soils in the northwestern part of the area are 

 terrace soils, occupying smooth areas lying a few feet below the 

 level of the Redding soils and several feet above the modern alluvial 

 plains. In most cases these are the terraces of the small streams 

 draining the western side of the valley, which carry local material 

 mainly, only their headwaters reaching back into the foothills of 

 the coast ranges. One of the laigest areas is on a well-develoi^ed 



