C. A. Reeds — Ilunton Formation of Oklahoma. 259 



the formation in the northeast corner of the Mountains. The 

 type locality is at the confluence of three small creeks, Sec. 4, 

 T. 2N., R. 6E. Since there were no geographic names in this 

 region suitable for formation names it was necessary to change 

 "South Fork of Jack Fork'' creek to Chimneyhill creek. The 

 Chimneyhill limestone rests unconformably on a blue, green 

 or yellowish shale which Taff has named the Sylvan. Above, 

 in most places, it is in contact with the Henryhouse formation, 

 which rests unconformably on it. In other places, as at 

 Ilunton, it is in contact with the Haragan shale, the second 

 shale formation, since erosion removed in that region all of the 

 Henryhouse before the Haragan was deposited on the uneven 

 surfaces of the Chimneyhill. 



Lithology. — From a lithologic standpoint the Chimneyhill 

 formation is divisible into three members: an oolitic limestone, 

 a glauconitic limestone and a pink-crinoidal limestone. Each 

 member has a variable thickness and extent throughout the 

 mountains. They will be considered in the order named, which 

 was also their order of deposition. 



Oolitic member. — This member forms a bed of oolitic lime- 

 stone ranging in thickness from to 12 feet, at the base of the 

 formation. Its best outcrop is in the northeast corner of the 

 mountains in the vicinity of Lawrence. There it has an aver- 

 age thickness of 9 feet, and is well exposed for a distance of 

 5 miles as the cap-rock to the escarpment of the Sylvan shale. 

 Although this member is generally present with the other 

 members of this formation it is absent in 10 of the 35 measured 

 sections and only 1 foot thick in 4 of them. Where it is only 

 1 foot thick the lower half is composed chiefly of crinoidal 

 fragments while the upper 6 inches consists wholly of oolite. 

 Where the member has an average thickness of 5 feet or more 

 the lower 1*5 feet consist chiefly of crinoidal fragments. Other 

 fossils are sometimes present. This narrow lower zone is often 

 of the same color as the overlying oolite beds, but perhaps it is 

 more frequently a brownish earthy crinoidal limestone. On 

 fresh exposures the oolitic limestone in the upper zone is light 

 gray to white in color, but where weathered it takes on a 

 darker tone. In hand specimens the oolites themselves may 

 be more or less uniform in grain, that is, fine, medium, or 

 coarse, or, those varying from a pinhead to a pea in size may 

 be associated together. This upper oolitic zone is chiefly 

 unf ossiferous except for a few small specimens of Favosites 

 niagarensis, and occasionally lentils of white limestone which 

 contain a new species of Clorinda. In the Coal creek sec- 

 tion a 6-foot yellowish shale bed, resembling the Sylvan, 

 occurs between 3 - 5 feet of oolite below and 1 foot of oolite 

 above. This is the only locality observed where a lentil of 



