MESOZOIC OF SOUTHWESTERN OREGON 547 



structural uniformity may be traced for miles, indicate crustal dis- 

 turbances and folding in the Dillard series before the deposition of 

 the Myrtle. 



A further argument for such physical activities during the Dillard- 

 Myrtle interval may be gathered from a consideration of the frac- 

 turing and crushing produced. These are characteristically present 

 in the Dillard exposures and are often excessive. In the Myrtle, 

 however, they are only locally in evidence to any marked degree, as, 

 for example, along an occasional fault plane or where the shales 

 have been folded against hard or massive formations. In the Dillard 

 we may connect this fracturing and crushing in part with the various 

 intrusions, in part with the swelling and moving of the solidified 

 serpentines, but a certain amount can be referred only to crustal 

 movement that was post-Dillard and pre-Myrtle. 



We may conclude, therefore, that the Myrtle group was deposited 

 unconformably upon the Dillard series after an interval of varied 

 igneous activity, earth movement, and erosion. 



COMPARISON WITH THE STANDARD CALIFORNIA TYPE 

 FORMATIONS 



THE MYRTLE GROUP 



Identity with the Shasta. — In describing the paleontologic limits 1 

 and characters 2 of the Myrtle group, and its nomenclature, 3 it has 

 been shown that it corresponds to the Shasta group of California, 

 and that the succession of horizons — Lower Knoxville group, Upper 

 Knoxville, Horsetown — is the same as in the Shasta group, and 

 characterized by the same fossils. It remains to be pointed out that 

 the lithological characteristics are identical, and, considering its dis- 

 tribution in connection with the known distribution of the Shasta 

 group, which is so strongly developed over large areas in northern 

 California, we may safely conclude that it is strictly Shasta, and 

 was deposited in the same sea, during the same period, and under 

 the same conditions of erosion and deposition as the Shasta of Cali- 

 fornia. 



THE DILLARD SERIES 



General characteristics 0} the Franciscan. — One familiar with 

 California Coast Range geology will already have anticipated the 



1 See p. 519. - See p. 522. 3 See p. 520. 



