544 GEORGE DAVIS LOUDERBACK 



THE COASTAL QUADRANGLES 



The Coos Bay quadrangle. — On the Coos Bay quadrangle there 

 are two main areas mapped as "Myrtle formation," both of which are in 

 the most southern part of the quadrangle, besides some disconnected 

 rocks and small bunches along the coast near Bandon. These are 

 apparently all Dillard. The writer studied the large area in the 

 vicinity of Myrtle Point, and found it made up entirely of typical 

 Dillard formations. No trace of the Myrtle group was found. That 

 all of the areas are Dillard, with no Myrtle, may be inferred from the 

 descriptions and mapping of the folio. No fossils (other than pro- 

 tozoan) were found, and in every small area, radiolarian cherts, 

 greenstones, glaucophane schists, alone or together, are distinctly in 

 evidence, while the semi-metamorphic sandstones make up the main 

 mass. 



The Port Orford quadrangle. — Considerable areas have been 

 mapped as the "Myrtle formation" in the Port Orford quadrangle. 

 The writer found time to examine only the northeastern portion 

 within about ten miles of its northern boundary. All of that portion 

 examined is distinctly Dillard, which is covered directly by the Arago 

 (Eocene) without the intervention of the Myrtle. The unconformity 

 between these two formations is well seen on Salmon Creek, about a 

 half-mile above its junction with the South Fork of the Coquille 

 River. The creek there flows on the contact, and the Eocene beds 

 on the east dip off regularly (at about 31 E.) from the highly inclined 

 (74 E. and over) and irregular Dillard beds. Pebbly layers in the 

 Eocene sandstones carry detritus derived from the neighboring 

 Dillard. 



Judging from the abundance of basalt, chert, small serpentine 

 dikes, and masses of amphibole schists, it may be inferred that most, 

 if not all, of the northern part of the Port Orford quadrangle is 

 Dillard, as far down perhaps as Sixes River. A considerable area 

 below this, through the midst of which runs Elk River, appears, on 

 the map, remarkably free from these diagnostic rock types, which, 

 however, again appear in part in the southwest corner, and in a 

 north-south belt just east of Iron Mountain. 



According to the text of the Port Orford folio, Horsetown and 

 Upper Knoxville fossils are found in the Rogue River section in the 



