1914] Buwalda: Pleistocene Beds in the Mohave Desert 447 



Lake. East of Afton the Mohave River has cut into what was 

 the east rim of the Manix Lake basin to a depth of perhaps two 

 hundred feet; the fanglomerates are there seen to arch over the 

 core of older rocks of this anticlinal barrier and to dip down the 

 east slope and disappear under the later fan deposits of the desert 

 to the east. 



The maximum thickness of the fanglomerates was not deter- 

 mined. Prom the sections exposed it is known to aggregate at 

 least several hundred feet. 



The fanglomerates are in general characterized by coarseness 

 and variety of constituent materials and by lack of distinct bed- 

 ding. The upper one or two hundred feet lying immediately 

 below the lacustral beds is commonly of somewhat finer texture 

 than the lowest visible strata. There is abundant and sudden 

 variation in texture both horizontally and vertically throughout 

 the section, as would be expected in an accumulation of waste- 

 slope origin. 



Along the north bank of the Mohave River, south of Field, 

 the lowest visible fanglomerates are made up of coarse angular 

 and subangular masses, commonly one to three feet in diameter, 

 consisting of granite, basic lava, rhyolite, schist, limestone, and 

 quartz, with little semblance of bedding. A part of the section 

 at this point consists entirely of black lava fragments of large 

 size. 



In the upper part of the exposed section the fanglomerate 

 consists of an abundance of angular and subangular fragments 

 enclosed in a yellow matrix. The fragments are basic and acidic 

 lavas and granite, ranging up to two or three inches in diameter. 

 The matrix is made up largely of quartz and feldspar grains 

 derived from the disintegration of granitic rocks. The whole 

 deposit exhibits the indistinct and irregular bedding commonly 

 seen in alluvial deposits. Some of the uppermost fine fanglom- 

 erate beds two miles south of Field can be traced laterally into 

 the coarser materials of the alluvial fans which extend up the 

 west slopes of the Cady Mountains. Some strata are composed 

 almost entirely of pink feldspar and quartz ; other thin layers are 

 unevenly bedded sands, probably of wind-blown origin. Well- 

 rounded river gravel is apparently absent from the fanglomerate 



