380 J. S. DILLER THE JURASSIC FLORA OE OREGON 



that they were at first regarded as Tertiary.* Near the base, however, 

 especially in the Wilshire mine, there are hard nodules cemented by car- 

 bonate of lime and iron. 



A 5-foot layer of fine conglomerate or breccia, locally at the bottom, is 

 made up almost exclusively of angular fragments of the schistose siliceous 

 rocks on which it rests with marked unconformity. Yery near the bot- 

 tom the shales are carbonaceous and pass into a thin bed of impure coal. 



STRUCTURE 



The structure of the area appears to be a short and shallow synclinal 

 basin, one arm of which is exposed in the Pattison mine and the other in 

 the Wilshire, with dips varying from 30 to 45 degrees. In both mines 

 the coal bed is exposed near the bottom, dipping generally in opposite 

 directions, and is conformably overlain by fossiliferous shales and sand- 

 stones. The continuity of the beds is interrupted by small local faults, 

 whose effect is to increase the apparent thiclaiess of the beds, and it is 

 probable that the thickness of 200 feet stated above is an overestimate. 



FOSSIL PLANTS 



Fossil plants have been collected in the Pattison mine near the middle 

 and the western edge of the upper terrace and at the eastern edge of the 

 lower terrace. In the Wilshire mine (old part) they have been found best 

 preserved in the hard portions above the coal. 



Fossil plants are most abundant in the lower portion of the pre-Tertiary 

 plant beds, but occur scattered irregularly throughout the strata, and all 

 belong to the same flora. They were referred to Dr P. H. Knowlton, 

 who reports the following forms: 



Dicksonia oregonensis Font. 

 Onychiopsis sp. (fruit). 

 Onychlopsis psilotoides Ward. 

 ' GladophJeWs sphenopteroides Font. 



Cladophledis vaccensis Ward. , 



CladophleMs denticulata ? Font. 

 GladophleMs sp. 



Scheropteris oregonensis 1 Font. 

 Tceniopterls orovillensis Font. 

 Twniopteris vittata Brongn. 

 TcBuiopteris sp. 



* There is some Tertiary near by. The fossil leaves found abundantly In the south or 

 new part of the Wilshii-e mine Knowlton regards as Tertiary. They are well preserved 

 in the fresh exposures of soft shales by the waste ditch of the gravel mined In 1907 near 

 the Chinaman's cabin. 



