406 Diller— Mesozoic Sediments of Southwestern Oregon. 



The section so well exposed along Grave Creek dips, with, 

 rare exceptions, to the S.E., and it is evident that if the gen- 

 eral structure of the Galice area is synclinal the southeast arm 

 must have been overturned towards the northwest so as to give 

 the strata a monoclinal attitude. .Strong evidence against the 

 synclinal view is afforded by a comparison of the two halves of 

 the Grave Creek section, for they are not repetitive but sup- 

 plemental. 



The narrow Y-shaped valley of Rogue River affords a good 

 section of the Galice area, just above the mouth of Galice 

 Creek the beds are much twisted and sometimes vertical, but 

 farther up the river the dip is from 25° to 50° S.E., and this 

 agrees with their position on Galice and Taylor creeks. The 

 slaty structure has the same position, and approaching the 

 eastern border of the area the fine sediments become so deci- 

 dedly slickensided as to suggest displacement. Below the 

 mouth of Galice Creek the strata with few exceptions dip to 

 the jST.W. at a high angle ranging from 65° to 80°, and at the 

 Almeda mine along the northwest limit of the area the slates 

 are practically vertical. 



Though the section of the Galice area along Rattlesnake 

 Creek suggests a synclinal structure, the view is not supported 

 by the Grave Creek and Rogue River sections, and overlook- 

 ing minor displacements within the mass it appears to be essen- 

 tially monoclinal and a continuous series with general dip to 

 the S.E. 



Limits of Galice formation. — The limits of the Galice forma- 

 tion are not fully determined. In the Galice area the outlines 

 are marked by the adjoining igneous rocks, but it is believed 

 that the full development of the Galice series is not repre- 

 sented in that area. On the South Fork of the Umpqua a 

 greater thickness of vertical black slate occurs. They closely 

 resemble those of the Galice series but are not yet known to 

 be fossiliferous. 



Relation to the igneous rocks bordering the Galice area. — 

 The igneous rocks bordering the Galice area northeast of 

 Rogue River are chiefly if not wholly volcanic, and the gen- 

 eral dip of the flows is to the S.E., approximately parallel to 

 the general position of the stratification in the enclosed Galice 

 area. This accordance would be expected if the Galice beds 

 of the Galice area are interstratified with the volcanics, a view 

 which may be favored also by the following consideration : 

 On Rogue River, east of the mouth of Galice Creek, some 

 tufaceous sediments and sheets of basic igneous rocks appear 

 interstratified with the fossiliferous sediments of the Galice 

 series, suggesting, contemporaneous volcanic activity ; others 



