C. W. Honess — Stanley Shale of Oklahoma. 11 



feldspar, sericite and other minerals masking the original 

 structure. Angular lithic fragments of slate, pieces of 

 limestone and sandstone of megascopic size are extremely 

 common as xenoliths and occasionally one sees a piece of 

 basalt in the tuffs. The feldspars are remarkably fresh 

 in most specimens and are medium acid in composition, 

 approximating that of oligoclase or oligoclase-andesine 

 ordinarily. Chlorite occurs in noticeable amounts for 

 the most part in large grains or blotches up to an inch in 

 diameter. 



The map accompanying this article gives all of the out- 

 croppings of the Stanley tuffs in the Lukf ata Quadrangle 

 as they have been mapped by the writer — all the outcrop- 

 pings having been located by pacing and checking on the 

 section corners. 



Following the tuff is a thick series, several hundred feet 

 over all, of hard and soft thin-bedded sandstones, slates 

 and shales, chiefly sandstones, which may be described as 

 fine- and uniform-grained dark greenish gray sandstones, 

 usually cross-bedded and often ripple-marked. 



This completes what is estimated to be about the lower 

 third of the formation. 



Succeeding these sandstones and continuing well be- 

 yond the middle of the Stanley, black shales and slates 

 become the predominating materials and instead of ridges 

 and wooded slopes one finds bushy flats and glades where 

 they outcrop. This transition to softer rock is not sud- 

 den nor are the shale masses entirely without sandstones. 

 The latter cease gradually, and by degrees they become 

 thinner and more irregular as time goes on until gritty 

 sediments practically are wanting. The shales are all 

 black or dark steel-blue in color and are well indurated. 

 Cone-in-cone concretions characterize a portion of this 

 subdivision of the Stanley and are found widespread 

 geographically. The thickness of the shaly portion has 

 not been estimated but there must be several hundred feet 

 of the shales. 



Passing upward one again encounters sandstones of 

 the bluish gray, massive, hard, resistant variety inter- 

 bedded with blue, hard clay shales, and these are suc- 

 ceeded by black cherty shales and thin-bedded black 

 cherts and flints. 



The black flints constitute a well-defined formation, in 

 themselves, of about 25 feet thickness and were encoun- 



