Diller — Mesozoic Sediments of Southivestern Oregon. 403 



Galice Formation (Jurassic). 



Definition. — The Galice formation is composed chiefly of 

 fine dark to black sediments with a well-marked slaty cleavage. 

 Subordinate amounts of sandstone and conglomerate occur and 

 the whole is characterized by an upper Jurassic fauna. It is 

 named from Galice Creek, where the rocks are well exposed. 



Lithology. — The slates are generally black and weather gray. 

 A well-developed slaty cleavage prevails, but locally they may 

 be shaly or on the other hand so sheared as to break up into 

 small slickensided fragments. Where massive, their stratifi- 

 cation is shown only by occasional thin beds of sandstone. 



The sandstones are light-gray, hard and siliceous, and though 

 much less abundant than slate form occasional heavy beds, but 

 more commonly are not a foot in thickness. 



The conglomerates, much less abundant than sandstone, are 

 composed chiefly of cherty quartz pebbles with some fragments 

 of sandstone or rarely of limestone. Igneous material is for 

 the most part absent, though sometimes abundant in tufaceous 

 rocks interstratified with the others. One bed of moderately 

 fine conglomerate is 30 feet in thickness. The others were all 

 less than ten feet, with pebbles smaller than marbles. 



Quartz veinlets are locally abundant in the slates parallel to 

 their cleavage and may fill numerous small irregular fractures 

 in the sandstone, but they are neither a conspicuous nor a reg- 

 ular feature. 



The stratification of the Galice formation is in most places 

 plainly marked. The strata have been greatly compressed and 

 folded but not crushed to small fragments. Incipient schistose 

 structure occurs locally with very little recrystallization along 

 lines of special disturbance, but it is neither a prominent nor 

 common feature. 



Distribution and thickness. — The Galice formation is dis- 

 tributed at intervals along a line running northeast from the 

 boundary of California to the South Fork of the Umpqua 

 River, a direct distance of nearly 100 miles. The most impor- 

 tant area extends from Galice on Rogue River in a slightly 

 irregular course northeast for 20 miles across Grave Creek to 

 Cow Creek, 2 miles below Glendale. This belt is from 2 to 3 

 miles in width, and continuous throughout, but is completely 

 surrounded by igneous rocks. It is the small Jurassic area 

 noted along Rogue River on the map of North America. The 

 strata, with but little variation, dip S.E. at an angle ranging 

 from 30° to 50°, and have a thickness of not less than 2.000 

 feet. Grave Creek affords an excellent section across the belt, 

 distributed approximately as follows : 



