410 Diller — Mesozoic Sediments of Southwestern Oregon. 



cut off by a mass of greenstone about the head of Thompson 

 and Jndd creeks but reappear on the Umpqua River by the 

 fording 3 miles northwest of Myrtle Creek post-office, where an 

 example of Aucella was found. This is apparently the same 

 horizon that occurs on Johnson Creek in the Port Orford 

 quadrangle, where striated Aucella have been found in loose 

 fragments but not in place. 



It thus appears that the only characteristic fossil yet found 

 in the Dothan formation is Aucella erringtoni, but that is so 

 well marked and so distinctive as to leave scarcely a doubt con- 

 cerning the Jurassic age of the formation. This reference is 

 strongly supported when we come to consider its relations to ad- 

 jacent terranes. 



Relation to adjacent volcajiic rocks. — The relation of the 

 Dothan formation to the volcanic rocks which bound it for 

 many miles upon the southeast has already been indicated in 

 considering the Cow Creek section whose contemporaneous lavas 

 and tuffs are found interbedded with the marginal portion of 

 the Dothan strata. The general dip of the Dothan formation 

 near the border is to the southeast beneath the great mass of 

 lavas. 



The contact of the Dothan formation with the overlying 

 volcanics along the eastern border of the main area is every- 

 where a zone of decided shearing, affecting both the sediments 

 and volcanics and producing not only slaty structure and slicken- 

 sides but entailing the local development of talcose and chlor- 

 itic schist-like material and considerable ore deposits. The 

 displacement, however, has not changed the apparent strati- 

 graphic succession, and the facts observed clearly indicate that 

 the Dothan formation at present is stratigraphically beneath 

 the mass of volcanics. 



Relation to adjacent Gcdice formation. — The mass of vol- 

 canics which overlies the Dothan series is the same that has 

 been shown to lie beneath the Galice series, and there seems no 

 doubt that the two series in their regular order of succession 

 are for the most part separated by an interval of volcanic rocks. 

 This succession illustrates their order of age unless they have 

 been overturned, a condition which is suggested by the planes 

 of displacement. 



At a number of points along Cow Creek and elsewhere stri- 

 ated fault planes were found rising to the northwest, generally 

 at a high angle but sometimes horizontal as though there was an 

 overthrust from the southeast. 



A suggestion that the Galice is older than the Dothan may 

 be found in the fact that the area occupied by the Galice lies 

 between that of the Dothan and the nearest Paleozoic on the 

 southeast. The most common dip among all the rocks is to 



