34 O. H. Hevsliey — Cretaceous Oittliers in California. 



consists of several hundred feet in thickness of a line pebbly 

 conglomerate, overlaid by a coarser conglomerate. The peb- 

 bles in the first are of quartz, have a remarkable uniformity 

 in size and are perfectly rounded. They weather out and 

 bestrew the surface as would a shower of marbles. They 

 unmistakably indicate marine action. 



Another supposed Cretaceous remnant is found at the 

 Sweepstakes mine, a few miles southwest of Weaverville, but 

 it has not been studied in detail and its extent is not known. 

 It consists of a hard conglomerate of fine pebbles resting on 

 the edges of the upturned Paleozoic slates and cherts. 



The first four areas are Horsetown in age. The diflPerences 

 which are observed between them in going southwestward are 

 exactly imitated by the basal beds of the Horsetown from the 

 village of Horsetown along the foot of the mountains to Har- 

 rison Gulch and Good's Pass. At Horsetown the basal beds 

 are shale and fine sandstone, as in the Indian Creek area. To 

 make the identification complete, both Diller and Anderson 

 have found the Horsetown fauna on Indian and Redding 

 Creeks. Westward from Ono, the basal bed of the Horse- 

 town is a heavy conglomerate like that of the Dobbin Gulch 

 area; and near Harrison Gulch, there occurs in the Cretaceous 

 the same peculiar pebble conglomerate as that of the Post 

 Creek area. 



Undoubtedly the sea of the Horsetown epoch transgressed on 

 the southeastern border of the Klamath region and deposited 

 probably several thousand feet in thickness of conglomerates, 

 sandstones and shales over what is now a rough mountain area. 

 At the time of the submergence it must have been compara- 

 tively even, but the heavy conglomerates tell of elevated and 

 perhaps mountainous land in the interior of the Klamath 

 region. 



This country, that became covered by the Horsetown sedi- 

 ments, had previously suffered profound denudation. At the 

 close of the Jurassic period, the stratified and already largely 

 metamorphosed formations of Mesozoic, Paleozoic and perhaps 

 earlier age, were intruded by three great series of batholiths, 

 the first of peridotite, the second of gabbro and the last of 

 granodiorite and allied plutonic rocks. These intrusions were 

 accompanied by orographic activity of the greatest magnitude, 

 for the whole area was thrown into a series of geosynclines, 

 with many minor folds and faults. At the close of the dis- 

 turbance the surface must have been very mountainous — a 

 mountain system, in fact, made up of quite different and more 

 massive ranges than those of to-day. Erosion slowly reduced 

 these mountains. Most of their destruction was accomplished 

 during the early Cretaceous time. Several thousand feet at 



