20 FIELD OPERATIONS OF THE BUREAU OF SOILS, 1910. 



The soils derived from the original valley deposits, occurring o)i 

 the eastern side of the valley, come from what is locally known as 

 '* lava flows." The soils are reddish brown or brown shallow soils of 

 little or no agricultural value. They occupy a sloping dissected plain 

 and are burdened with great quantities of bowlders of varying size 

 derived from volcanic rocks. An impenetrable mass of cemented 

 waterworn gravel is encountered at a depth of a few inches and ex- 

 tends to great depths. These are probably the most hopeless soils of 

 the area and are classified as the Tuscan series, represented by two 

 types. They are derived from valley deposits probably of the same 

 age as the Ked Bluff deposits, but derived from the volcanic rocks of 

 the Lassen Peak region. The great body of the deposit is a coarse 

 mass of rather well-worn pebbles and bowlders of volcanic rocks with 

 interstratified beds of finer material, the latter including some beds 

 of tuff. The series is separated on its lowest edge from the Sacra- 

 mento bottoms by sharp bluffs '20 to GO feet high. It is extremely 

 arid, unproductive, and capable of little development. Ages ago it 

 occupied a much greater extent than at present, but processes of ero- 

 sion have removed the material over Avide areas and other areas have 

 been covered with alluvium. 



The Vina series, consisting of four types, is confined to the east 

 side of the valley. These soils are alluvial in character and the 

 product of the numerous east side streams. They occupy sections 

 occurring as valleys or deltas once occupied bj'^ the Tuscan series. 

 The series is usually separated from the Tuscan series by marked 

 terraces, but at its lower edges it merges gradually into the slightly 

 lower Sacramento series. These soils are in the main brownish or 

 dark gray in color, friable, and productive. Some of the members 

 constitute the best soils of the area, while one or two are unproductive. 



The soils of the great alluvial flood plain of the Sacramento, which 

 traverses the area, were classed here, as in the other areas surveyed in 

 the valley, as the Sacramento series. Four types were recognized and 

 correlated with previously recognized types. These soils are the 

 direct product of sedimentation by the Sacramento River, the ma- 

 terials being derived along its upper course. The}' are light gray or 

 dark gray in color, slightly micaceous, and of variable textures and 

 indistinctlv sepai-ated from each other. A deep soil and friable 

 structure are the rule. The series comprises the most productive 

 soils in the area. It occurs as a broad, level plain marked by over- 

 flow channels with considerable sections subjected to flooding. A 

 marked terrace bounds its outer limits and the river occupies a wind- 

 ing channel 10 to 20 feet deep through its level surface. 



The great variability in the soils of the Red Bluff area makes few 

 geneial -tateniciits j)()ssibl('. Tiiey are usually well drained and pro- 

 ductive whenever moisture conditions are favorable. It is no doubt 



