SOIL SURVEY <>F SOLOMONSVILLE AREA, ARIZONA. 9 



of moderate^ fine texture. Near the mouths of extensive canyons 

 and washes occur deposits of sand, usually of coarse texture. Through- 

 out the deposits of the foot slope gravel occurs in large and quite 

 uniform quantities. The surface is frequently entirely covered with 

 tine angular gravel of volcanic origin, which, when embedded in the 

 soil, forms a hard, smooth surface. In other positions the gravel 

 consists largely of granitic fragments, with considerable quartz, feld- 

 spar, and other common rocks. Wherever the foot slopes are cut by 

 streams prominent bluff and terrace lines are formed. These are 

 sometimes quite extensive and often very abrupt. In the vicinity and 

 covering the edges of these terraces gravel deposits also occur, the 

 fragments varying in size from that of a pea to small, well-rounded 

 bowlders. 



The terraces are often deeply cut by small washes and canyon 

 streams heading upon the terrace levels and forming a secondary s} T s- 

 tem of canyon mouths and fans upon the valley bottom below. Hori- 

 zontal beds of drab or gray-colored sandstone, underlying the surface 

 material of the foot slopes, are f requently exposed in the deeper*cuts 

 along- the foot-slope margins. Strata of clays and shales in advanced 

 stages of decomposition often occur interbedded with the sandstone. 



The strata of gravel are often cemented into a calcareous hardpan 

 exposed along cuts and margins of the terraces. This material fre- 

 quently caps the mesa lands and covers the softer earths and rocks 

 below. 



The character of the material of the secondary foot slope is similar 

 to that of the main foot slope above, from which it is derived. The 

 surface of the fans is usuall} 7 of gentle slope and covered only with 

 scattered cacti of various species, yucca, greasewood, and various 

 other desert plants. 



The river bottom or valley trough occupies a tract from 1 to 5 miles 

 in width, through which flows the Gila River. The river course has 

 been partially refilled b}- alluvial sediments. The Gila River and its 

 tributaries carry in suspension a vast amount of sediment which is 

 deposited in considerable quantities along the river flood plain during 

 high water. The cutting away of the stream banks as the stream 

 shifted from side to side has produced the level bottom, flanked by 

 the steep slopes of the terrace-bordered mesa lands. From the valley 

 trough the bottom extends outward with gentle slope to the bluff 

 lines marking the margins of the mesa lands. Small terraces of recent 

 origin frequently occur in the valley bottom. The material consists 

 of alluvial deposits ranging from silts and sands to coarse gravel. 

 Near the base of the terraces marking the valle}- borders these alluvial 

 deposits are frequently overlain by wash from the mesa lands and 

 canyon streams. Portions adjacent to the river channel are f requently 

 occupied by extensive deposits of fine river sands of uneven, wind- 

 blown surface and covered with a heavy growth of willow and 

 cottonwood. 



