MESOZOIC OF SOUTHWESTERN OREGON 545 



southeast corner of the quadrangle. This section is estimated as 

 1,500 feet thick, and is said to be made up of "much shale mixed 

 with the relatively thin-bedded sandstone, and although the rocks 

 are highly tilted, their stratification is well preserved." Further- 

 more, "the base of the series on Rogue River below Agnes is a heavy 

 conglomerate, best exposed perhaps in a prominent bluff near the 

 trail one and one-half miles northwest of Agnes. A. crassicollis, 

 which is the later form, characterizes this portion of the section where 

 it is separated from the Colebrooke schist by a belt of serpentine." 

 This is evidently a section of the Myrtle group, and we may infer a 

 gradually depressed sea bottom as the Upper Knoxville horizon has 

 overlapped the lower, and lies directly on the pre-Myrtle rocks with 

 a basal conglomerate. 



The most extensive fossiliferous section described is on "Elk 

 River, beginning to the east in Copper Mountain with large masses 

 of conglomerate and sandstone overlying shales and sandstones, the 

 whole containing A. ■piochii.' n Farther down the river, "shales and 

 sandstones are well exposed and contain numerous fossils in place." 

 These are referred to the Upper Knoxville by T. W. Stanton. The 

 Elk River section is, therefore, as already inferred from inspection of 

 the map, chiefly, if not wholly, of the Myrtle group. 



In the northwestern part of the quadrangle occurs an outlier of 

 the Klamath Mountains schists, upon which the Myrtle group lies, 

 "and the basal portion is a conglomerate containing many fragments 

 of the schist. The conglomerate commonly contains Aucella crassi- 

 collis. " We had thus repeated the phenomena of overlap of the 

 Upper Knoxville horizon over the lower and onto the schists, as 

 already described for the Rogue River section, which is about twenty- 

 five miles distant. 



THE DISCONTINUITY OF THE DILLARD AND THE MYRTLE 



Where the exposures of the Myrtle group have been observed in 

 close proximity to those of the Dillard series, there was found no 

 gradation from the lower to the higher formations, but a distinct 

 break in lithologic character and structure. The evidence already pre- 

 sented is to the effect that this break represents a period during which 

 many events were brought to pass which we may believe required 



