1921] Friclc: Faunas of Bautista Creek and San Timoteo Canon 317 



The structural axis of the San Timoteo fold lies within the 

 southern area and considerably to the south of the present crest. 

 The trend of the strike is to the east and west of the compass. The 

 respective limbs of the major fold pass to unknown depth beneath 

 the recent alluvium of the north and south valleys. The occurrence 

 at the edge of the Badlands in the Moreno Valley of strata which 

 have a rather constant dip of 35 degrees southwest, together with 

 the marked evidence of great faulting along the same line a short 

 distance to the east in the Claremont region, strongly suggest the 

 presence of a break along the valley line. Borings in the valley have 

 never revealed the distance to bedrock, this on the San Bernardino 

 side lies a thousand or two thousand feet below sea level and thus 

 affords strong proof of the one-time subsidence of the region. 



South of Beaumont, where monadnock-like bosses protrude through 

 the sedimentary crust, as in the Crafton Hills, and again in Reche 

 Canon, coarse San Timoteo beds are seen in direct contact with the 

 old eroded basement surface. In their southeastern extent, these same 

 upper San Timoteo beds are found unconformably overlying an earlier 

 more indurated and, generally speaking, finer series of sediments, the 

 lower San Timoteo or Eden beds. The Eden series, in the same 

 manner as the upper deposit, is found in places in direct contact with 

 the basement metamorphics. To the southeast, in the Potrero Basin, 

 it occurs overlying beds of coarse arkosic, which there intervene 

 between it and the complex of older rocks exposed in the foothills of 

 the San Jacinto Range. 



UPPER SAN TIMOTEO DEPOSITION 



There is a material difference between the north and south flanks 

 of the long Badlands ridge of the San Timoteo. The northern exposure 

 rises by gentle-dip slopes, thickly brush grown, to near-by crests ; only 

 here and there do the bluffs appearing at the sides of its short valleys 

 afford an occasional view of north-dipping bedding planes. The south- 

 ern flanks, on the other hand, fir.st plvxnging abruptly downward by 

 steep contra-dip faces, and then falling away to the distant valley by a 

 long broken series of twisting knife-edged ridges, afford fine exposures 

 of somewhat broken but generally south-dipping strata in many an 

 east- and west-facing bluff. Here the usual dearth of south side 

 vegetation has assisted the process of erosion. 



