O. H. Hershey — Cretaceous Outliers in California. 35 



least of Mesozoic slates and meta-andesites were removed and 

 the rivers cut deeply into the Paleozoic slates beneath. The 

 denudation reached even to the plutonic masses and laid bare 

 the coarse-grained gabbro and granodiorite which must have 

 solidified at a considerable depth beneath the surface. As 

 products of this erosion and of that accomplished in the Sierra 

 Nevadas at the same time, we have in the Coast Range region 

 many thousands of feet of sandstone and shale, the first chiefly 

 Franciscan and the latter Knoxville in age. Judging from 

 the work performed, this "early Cretaceous" period must 

 have been a very long one, perhaps equal to all the time since. 



Base-leveling in the Klamath region continued through the 

 Horsetown and Chico epochs. J^ortheastward from Horse- 

 town the Chico formation laps past the Horsetown and from 

 Clear Creek to far beyond the Sacramento River it is in con- 

 tact with the metamorphic rocks as shown by Diller and 

 others. The basal bed of the Chico is a fine sandstone, with 

 no conglomerate whatever present in this area. Apparently 

 the southeastern border of the Klamath region had been pretty 

 thoroughly base-leveled before the opening of the Chico epoch, 

 but the northeastern border seems to have still remained hilly, 

 since the base of the Chico in Shasta Yalley and the Siskiyou 

 range is a heavy conglomerate. It is probable that even to 

 the close of the Cretaceous, the central portion of the Klamath 

 area remained elevated, but base-leveling had been affected 

 around its borders, and a very slight depression was sufiicient 

 to cause the Upper Cretaceous strata to lap over on to it. 



Subsequently to the Chico epoch there occurred another 

 profound orographic disturbance of the Klamath region. It 

 was characteristically different from that which closed the 

 Jurassic period. Much of the area and perhaps all seems to 

 have been deformed into a series of deep, elliptical basins. 

 The four principal Cretaceous remnants in Trinity County 

 mark the deepest portions of four of these structural basins, 

 each of which was elongated in a direction west-southwest, 

 adjoined each other and virtually constituted a syncline sepa- 

 rated from the Sacramento Yalley by a rather prominent anti- 

 cline. Perhaps my meaning may be clearer if I state that the 

 four Cretaceous remnants are separated from each other by 

 tracts of metamorphic rock which rise about 2000 feet above 

 the deepest portions of the basins, but that the ridge of meta- 

 morphic rocks which separates them from the Cretaceous in 

 the Sacramento Yalley is much higher. 



The average altitude of the bottom of the Cretaceous in the 

 center of each basin is about 2500 feet. The ridge which 

 separates them from the Sacramento Yalley rises from an alti- 

 tude of about 4000 feet at Harrison Gulch to over 7000 feet 



