calcareous sediments which have a lighter texture. These 

 soils are normally free from alkali and other salts, except 

 on the lower portions of the alluvial fan where drainage is 

 restricted. Parent materials aj?e a mixture of marine and 

 nonmarine sediments. 



The soil series having the greatest amount of tiled acreage 

 is the Lost Hills series, followed by the Rincon and the 

 Ambrose series. 



Soils of the Basin Rim Position . Four major series make up 

 the bulk of basin rim soils in the study strea. These aire 

 Oxalis, Lethent, Levis, and Willows. These soils occur in 

 the Gustine-Mendota area at the outer edges of alluvial 

 fans along the shoreline of a former shallow inland lake. 

 Parent materials are fine-textured, calcareous alluvium that 

 originate from softly consolidated sandstones and shales. 

 These soils are fine-textured, and, unless modified by 

 irrigation, are characterized by strong concentrations of 

 alkali and gypsum throughout the profile. 



The most extensive basin rim soil belongs to the Oxalis 

 series, which is associated with soils of the Panoche series 

 but is typically darker, finer textured, and subject to slow 

 surface drainage. The substratum is very often stratified 

 with fine silty material that creates temporary perched 

 water conditions. 



The Lethent, Levis, Willows, and Oxalis soil series are very 

 closely related and were originally mapped as a soil complex. 

 Many tile drains are located in the abundant Oxalis series. 



Soils of the Basin Position . Soils lying within the basin 

 or trough position are generally fine-textured and dark and 

 contain less surface alkali than do the soils of the basin 

 rim. Parent materials are derived from mixed granitic 

 sources from the Sierra Nevada. 



The largest tiled acreage within the basin position is the 

 Tulare series, which occupies the Tulare lakebed. Soils of 

 this area are flat and poorly drained and at one time 

 supported a great growth of tules. Salts contained within 

 the highly stratified profiles tend to move to the surface 

 unless prevented by frequent irrigation or ponding. 



The soils of the Columbia series, represented by two systems 

 located in the northern area, have been subject to frequent 



25 



