Diller — Mesozoic Sediments of Southwestern Oregon. 409 



mass of conglomerate in the latter near the middle, forming 

 prominent outcrops for several miles along Rogue River be- 

 tween Ditch and Kelsey creeks. The conglomerate is made 

 up in part of limestone fragments and is so crushed as to 

 obscure its folding. The rest of the section is made up of 

 alternating sandstone and shales in variable but on the whole 

 nearly equal proportions. They are greatly compressed and 

 often sheared so that the sandstones appear as small lenses in' 

 the shales. Their dip is variable but generally southeast at a 

 high angle. 



Southwest of Rogue River the belt of Dothan is narrowed 

 by the advance of the overlapping Cretaceous and Eocene 

 formations. Beyond the Illinois, although traversed at a num- 

 ber of points to the coast, the country has not been sufficiently 

 studied for mapping. 



The thickness of the Dothan formation is difficult to deter- 

 mine owing to its disturbed condition, but it is certainly more 

 than a mile and perhaps more nearly 2 miles. The belt is 

 about a dozen miles wide where greatest, and no definite 

 evidence could be obtained tending to show a repetition of any 

 horizon. The faulting, as will be noted presently, tends to 

 decrease rather than increase the apparent thickness. 



Fossils and age. — Fossils have been looked for with care at 

 many places on the Dothan formation and their general scarcity 

 or absence contrasts this series with the Galice (Jurassic) on the 

 one hand and the Myrtle (Cretaceous) on the other. Excepting 

 the radiolaria of the chert and problematical wormtracks and 

 leaf fragments which have been found at various horizons, 

 definite fossils are known to occur only near the northwestern 

 border of the main area in the vicinity of Nichols Station or 

 in a small area on Doe Creek and Thompson Creek, 11 miles 

 farther northeast. 



The Nichols Station localities are in the sandstone and fine 

 conglomerate of a small gulch about half a mile northwest of 

 the post-office and on Table Creek near Logsden's place. A 

 collection made by Mr. Will Q. Brown last summer at the 

 last-named locality contains forms which are distinctly striated 

 and leave no doubt concerning their specific determination as 

 Aucella erringtoni. The rocks containing them are twisted 

 and crushed but not silicified, and contain only veins of calcite. 



On Doe Creek and Thompson Creek, Aucella have been 

 found at a number of points but chiefly near Lost Prairie, a 

 mile and a half northwest of Nickel Mountain, where they 

 occur in a sandstone which is decidedly sheared and shows 

 incipient schistosity cut by veins of quartz. 



Associated with the fossiliferous silicified sandstone on Doe 

 Creek is a considerable thickness of black slate. These rocks are 



