316 University of California Publications in Geology [Vol. 12 



At the close of this epoch . . . movement was resumed along the lines followed 

 during the earlier period . . . [lifting] the San Bernardino Mountains to their 

 present elevation . . . [and] the earlier deposited alluvial wash into the sloping 

 mesas of Smiley Heights and Eedlands Heights . . . the Yueipe bench to a position 

 somewhat higher than it had occupied before, and the coarse boulder beds south 

 of San Timoteo Canon [the Badlands] were given the strong northern dip which 

 they now have . . . [while] San Bernardino Valley seems to have again subsided. 

 After this readjustment . . . erosion became more active than ever, the present 

 deep canons were cut, the modern fans were built, and the great [later] alluvial 

 filling which makes the present surface of the San Bernardino Valley and serves 

 as such a valuable storage reservoir . . . accumulated. 



The "working hypothesis"-'' of Dr. Mendenhall while in the field, 

 based on induration and physical character, held the cobble beds at 

 the top of the Badlands alluvium as late Pliocene or early Pleistocene, 

 and the finer beds at the bottom as probably Pliocene and perhaps 

 late Pliocene in age. He states that the only fossils collected were a 

 few shells, secured in a shaft in a carbonaceous streak in the gritty 

 clays of the area, which Dr. Dall reported as belonging to brackish or 

 fresh water types that might represent any period from the Miocene 

 to the present. 



The canon of the San Timoteo divides this long sedimentary area 

 diagonally from southeast to northwest into two natural topographical 

 subdivisions, a low-rimmed northern and a higher-rimmed southern 

 portion. The present investigation was confined to the latter portion. 

 Its desolate waste forms the so-called Badlands, which stretch east and 

 west in striking contrast to the watered mesas of Tucaipe and Redlands 

 that lie beyond the northern wall. Long benches at the mouth of 

 the San Timoteo Caiion point to the antecedent nature of the lower 

 portions of its stream and to the unity of deposition, as well as to the 

 slowness of the general uplift. The stream in its higher reaches is 

 joined by two washes, that drain the upper area of the main plateau 

 and unite with a third from the more northern portion of the same. 

 Broad, deep levels, which former meanderings of the three streams 

 have cut into the Beaumont floor, line the troughs of the present 

 constricted washes. It is interesting to note that while the canon 

 of the San Timoteo on the north side of the Badlands has worn its 

 way westward in the direction of the normal drainage of the San 

 Bernardino basin, the slope of the Moreno Valley, which cuts and 

 limits the Badlands on the south, is to the east. 



20 Personal communication by Dr. Mendenhall. 



