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erosion of the region, the high terraces indicating the former 

 valley bottom or floor before the region was uplifted to its 

 present height. 



Beyond Saugus, after crossing the bridge over Santa Clara 

 River, the truncated edges of steeply dipping rock formations 

 (of Pleistocene age) are overspread with gravel deposited by 

 meandering side-cutting streams. A few miles east of Saugus 

 Mint Canyon and Soledad Canyon come together. The South- 

 ern Pacific Railroad follows the course of Soledad Canyon in 

 its climb over the mountains to Mojave Desert. The Santa 

 Clara River, which flows through Soledad Canyon, has cut its 

 channel deeply, and mostly has eroded through the sedimentary 

 formations into the metamorphic and granitic rocks such as 

 form the main parts of the San Gabriel Mountains. 



Through Mint Canyon and Sierra 

 Pelona Valley 



The highway follows Mint Canyon. About 13 miles east 

 of Saugus the valley becomes more canyon-like, and changes 

 from a wide flat-bottomed valley in which the stream cuts its 

 banks but does not erode its bottom to a steep-walled V-shaped 

 valley in which down-cutting of the bottom is active. This is 

 the real Mint Canyon. The change is due to the higher gradi- 

 ent of the stream as it descends the slope of the mountain range 

 of Sierra Pelona, which rises to the north. In its upper course 

 Mint Canyon loses much of its canyon-like character and be- 

 comes a flat-bottomed valley with steep walls and bordering 

 terraces as it crosses the gently sloping plain of Sierra Pelona 

 Valley with lower gradient. Nineteen miles east of Saugus the 

 highway winds up the side of Mint Canyon and passes through 

 a deep cut to Sierra Pelona Valley. 



To the north is the eroded escarpment of Sierra Pelona 

 Mountains, the highest peak of which is Mount McDill, 5,180 

 feet. Sierra Pelona Mountains were formed by the crumpling 

 and metamorphosing of sedimentary formations. The intru- 



