126 University of California Publications in Geology [Vol. 7 



topography characteristic of the lower beds the upper member 

 forms low hummocky mounds rising here and there above the 

 mantle of alluvial debris. At the locality four miles north of 

 Rieardo post-office fine buff beds are capped by a dark resistant 

 layer of subangular to angular bowlders, some of which are as 

 large as a foot and a half in diameter, of very vesicular basalt, 

 red porphyritic lava, red lava showing flow structure, chert, 

 finely-laminated slate, and quartz. This capping is very local 

 in extent and is probably a stream deposit. 



Fossils are probably to be found throughout the entire thick- 

 ness of the Rosamond series. They have been reported from the 

 basal beds in the placer diggings in Bonanza Gulch about one-half 

 mile east of the lower narrows of Red Rock Canon, but no fossils 

 were collected from the basal beds by the writer or his associates. 

 Mr. George E. Stone found the skull and tusks of a mastodon 

 in place about 400 feet stratigraphically below the lower basalt 

 flow in Iron Canon, the main gulch tributary to Red Rock Canon 

 on the east, about two and one-half miles east of Red Rock 

 Canon. The mastodon remains are in rather fine greenish-gray 

 tuff interbedded with coarser conglomerate layers about 200 feet 

 stratigraphically below the massive pink tuff-breccia of the Red 

 Rock Canon section. This is the lowest definitely known fos- 

 siliferous horizon. Fossils were found in the very topmost beds 

 exposed, but are apparently most abundant in the 300 or 400 feet 

 of beds lying next above the upper basalt flow. The fossil 

 remains are fragmentary and were often checked and broken 

 before burial. The fossil forms found include horses, camels, 

 merycodonts, mastodons, canids, and felids. They probably place 

 the age of the Rosamond series as not older than the Upper 

 Miocene. The definite assignment of age to the fauna cannot be 

 made until it has been studied in detail. 



THE BLACK MOUNTAIN BASALT PLOW 



The even surface of bevelled Rosamond strata is overlain on 

 the summit of Black Mountain by a flow of olivine basalt. The 

 basalt is both vesicular and compact in habit. The flow is a 

 thin one. probably less than 100 feet in thickness at a maximum, 



