488 INDEX TO THE STEATIGEAPHY OF NORTH AMERICA. 



of sandstone, and a western area in whicli the sandstones are mostly wanting. In the present 

 state of knowledge it is impossible to draw an accurate line of separation between these two 

 areas, and for this reason the strata in them are not defined as separate members. 



The eastern area of the Enid formation is triangular and occupies several counties in the 

 central part of the Territory, in which there is little hard rock of any kind. 



Throughout this area the soil is red, except where later deposits cover the uplands or 

 among the sand hills north of some of the streams. Red clays and occasional ledges of thin 

 sandstone outcrop along the bluffs of a few streams. 



The rocks of the western area of the Enid consist chiefly of red clay shale, some inconspicuous 

 ledges of soft sandstone, and occasional bands of whitish or greenish shales, which vary from 1 

 inch to several feet in thickness. The upper strata are in some places highly gypsiferous, and at 

 some localities brine springs issue from them. 



The Blaine formation consists of red shales with interbedded strata of gypsum and thin 

 ledges of dolomite. It includes the portion of Prof. Cragin's Flowerpot formation above the 

 base of the Ferguson gypsum and all of his Cave Creek formation. It is named from Blaine 

 County, Okla., where it is typically developed. 



The characteristic which justifies its recognition as a formation is the abundance of gypsum 

 contained in it, and its extent and limits are defined accordingly. The bottom of the lowest 

 massive gypsum bed — the Ferguson gjrpsum member — is the base of the formation throughout 

 its occurrence northwest from Darlington, Canadian County. Where it disappears the shales 

 of the Enid continue up to the base of the Medicine Lodge gypsum member, which necessarily 

 becomes the basal member of the formation. The top is the Shimer gypsum member. Where 

 the gypsum members run out, as they all do north of Darlington, the Blaine can not be dis- 

 tinguished readUy from the Enid below and the Woodward above, and this local division of the 

 red beds can not well be traced. 



The thickness of the Blaine formation varies considerably with the locaUty, but it averages 

 about 76 feet. 



Above the Blaine are approximately 300 feet of rocks consisting chiefly of shales, sand- 

 stones, and dolomites and distinguished from the formations above and below by the promi- 

 nence of dolomites and the absence of gypsum. The formation includes all the rocks between 

 the two conspicuous gypsum horizons, the Blaine and the Greer, and in general it may be 

 divided into three members — the Dog Creek, the Whitehorse, and the Day Creek — ^which were 

 all recognized and named by Prof. Cragui from localities in Kansas, except that his term Red 

 Bluff was preoccupied, and for it the name Whitehorse has been substituted. For the forma- 

 tion as a whole, from the top of the Shimer gypsum to the base of the Chancy gypsum, the name 

 Woodward is proposed, from the county in Oklahoma where the strata are weU represented. 



^ vU •t «1* 4* 4^ Sc Hz ^ 



Above the Woodward formation are red clays, shales, and sandstones, and intercalated 

 beds of gj^sum and magnesium limestone or dolomite 150 to 300 feet thick. Gypsum is the 

 characteristic deposit of this formation, as it is of the Blaine. The formation for which the 

 name Greer is proposed, from the county in southwestern Oklahoma where it is weU exhibited, 

 is exposed over a very irregular area. For purposes of discussion it may be grouped according 

 to two general areas, an eastern and a western. 



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The rocks of the eastern area of the Greer formation strike northwest and southeast just 

 west of the outcrops of the Woodward formation. They are chiefly red clay shale, interstrati- 

 fied at several horizons with red sandstone and gypsum, which are, however, very irregularly 

 bedded and can rarely be traced as continuous or definite ledges. Nevertheless, the thickest 



