GEOLOGY OF THE SILVER CITY AREA 421 



W. L. Ainsworth. The work was done in the interest of the Fredonia 

 Gas Company, through whose courtesy publication is permitted. In the 

 preparation of the article the writer had the advantage of suggestion and 

 criticism from Professors C. K. Leith and A. jST. AYinchell. 



Geology of the Silver City Area 

 tee local section 



Before considering in detail the altered rocks it is thought best to give 

 a brief description of the geology of the area surrounding Silver City 

 ridge, in order to define the formations and to afford data for contrasting 

 the altered rocks with the unchanged. 



The local section includes two of the great sand-shale and two of the 

 limestone members of the Kansas Coal Measures. In describing these 

 divisions, the lithology normal to each is given, \\'hile the variations due 

 to alteration are left to subsequent paragraphs. Only such details are 

 given as have a bearing on the problem. 



LAWRENCE SHALES 



This, the topmost division of the local section, consists of red, yellow, 

 gray, blue, and black shales and sandstones of ferruginous colors. The 

 division is hio-hly cross-laminated, of variable stratification and lithologv 

 in both tlie horizontal and vertical sense, and is generally of crum])ling 

 texture. Generally there are mauy bands of shale and sand which con- 

 tain mica (apparently muscovite) in great abundance. The thickness is 

 variable, but generally exceeds 150 feet. About 50 feet remain on the 

 east tip of Silver City ridge. 



lATAN (KICKAPOO) LIMESTONE ^ 



'J'his division is one of the most easily recognized of the Kansas Coal 

 Measures aftd, for a thin member, its horizontal extent is remarkable. 

 The upper layer is a compact, very dark blue, semicrystalline limestone 

 of fine texture and brittle fracture. The farmers describe it as flinty. 

 It is characterized by a highly developed vertical jointing, with the joint 

 planes meeting at oblique angles. The thickness of this layer varies be- 

 tween 1 and" 2 feet. Below the upper layer are from 2 to 10 feet of strata 

 of variable lithology with those of limestone composed for the most part 



* The name "latan" was applied to this limestone by Keyes, Am. Geologist, vol. 23, 

 1 ><!)(>. p. .306. Subsequently Ha worth and Rennett (Kansas University Geol. Surv,, vol. 

 ix. r.ios. p. lo.ji proposed the name of ''Kickapoo." Since the former has priority, it 

 Is here used. 



