0. H. Hershey — River Terraces of California. 247 



in the hard Franciscan sandstone just below Korbel. The 

 degree of preservation of this terrace, and its relation to lower 

 terraces in the same valley, constrain me to consider it practi- 

 cally the equivalent of the main upper terrace (that occurring 

 so persistently at several hundred feet above the streams) on 

 the Trinity, Klamath and Sahnon Kivers. The Mad River 

 terrace seems to slope toward the sea at a rate which was 

 certainly not original. It may connect with a marine terrace 

 back of Eureka. 



]Near Bay Yiew station, on the railway between Eureka and 

 Areata, there is a much eroded terrace rising probably 75 or 

 100 feet above the bay. An extensive railway cutting exposes 

 false-bedded brown sand and silt, evidently marine. This 

 terrace I consider the equivalent of one of the upper river 

 terraces inland. It is developed in the town of Areata where 

 it consists largely of a yellowish, non-pebbly silt resembling 

 weathered loess, l^orth of Areata there is developed a lower 

 terrace which consists of a bed of irregularly stratified gravel 

 overlaid by silt. Its outer edge rises probably 15 to 20 feet 

 above the Humboldt Bay lowland or alluvial plain. This 

 terrace I correlate with the lower terrace (the broad valley 

 floors) of the Trinity, Klamath and Salmon Rivers. The town 

 of Eureka is largely built on a low, flat terrace of brown sand, 

 whose outer edge rises probably 15 to 20 feet above the bay 

 and may be of the same age as the lower river terrace inland. 



The main upper terrace, occurring so persistently at several 

 hundred feet above the Trinity, Klamath and Salmon Rivers 

 in the area herein discussed, seems to be approximately of the 

 age of the Red Bluif formation. The canons excavated by the 

 Sacramento River and Clear Creek since the uplift of the Red 

 Bluff formation, are fairly comparable with those eroded on 

 the western slope of the Klamath Mountains since the streams 

 began to cut below the main upper terrace. I should say that 

 throughout the Klamath region the post-Red Bluff erosion 

 nowhere exceeded a depth of 500 feet, unless in a few limited 

 areas which were exceptionally tilted, areas which have not 

 yet come to light. It has been prevailingly from 200 to 300 feet 

 in depth, reaching 400 feet locally. The post-Red Bluff 

 erosion , constitutes at least the last one-fifth and probably the 

 last one-tenth of the erosion of the Sierran or Pleistocene 

 canons. 



The low terrace at Eureka and the low gravel terrace at 

 Areata I attribute to the San Pedran subsidence which seems 

 to have been quite persistent along the coast of California. 

 The development of the broad valley fioor, constituting the 

 lower terrace on the Trinity, Klamath and Salmon Rivers, I 



