265 



circular (iiitci-dp. lnit llicy <'niiriisc(l llic .Miirfrccslxiro ami Uldlcy liincstoiics 

 at this time. 



The Murfrccslioro liiiu'stoiic is the oldest fonnatioii oxiKiscd on tlic Xasli- 

 ville dome and outcrops only in lint iicrford County upon the crests of 

 secoiidiu-y upfolds that occur aldu.u- the valleys (d" Stones River and its 

 tributaries. Thus, instead of a sin.i^lc area in which the formation appears 

 at the surface, there are nuinerous small and isohited localities. 



The beds consist of thiclv layers of bluish gray, dense, bituminous lime- 

 stones with much disseminated ch(>i't which appears upon weathered sur- 

 faces in small irreirular masses. At I-ascassas. Rutherford County, the 

 lower fifteen feet of the t\\-eiily-se\-en feet ex])osed consists of sandy, lam- 

 inated, ripple-marked and sun-cracked limestone, which is i'\ idence that 

 the sea was shallow and the shore line ]irobably not far distant durint; the 

 closing stage of the deposition of the .Murfreesboro limestone. 



Fossils ai-e few and difiicult to obtain from the unweathercd limestone; 

 but in the residuum resulting from the weathering of many feet of the 

 formation, and in the cherty masses upon the surface of the exposed rock, 

 silicitied specimens occur in considerable abundance. Some of the best 

 localities are near the Central Noinial School, at Murfreesboro, and upon 

 the bluffs of Stones River near thi' Xasbville pike. Salterella billingai, 

 ljOI)fi()sj)ir(i ixraiif/iildtd. Lio.spiro nhniiiUi. Ilclicotoma tennessecnsis, H. 

 (Icclirix are the most abundant species and are characteristics of the foi-ma- 

 tiou. 



Tlie maximum exposure of this limestone is seventy feet, with the basal 

 beds not exposed. 



Pierce Vimvulouc. This formation was named by Safford^ in 18G9. from 

 the splendid outcrop near Pierce's Mill, one-half mile south of Walter Hill, 

 Rutherford County. It consists of several lithological members as fol- 

 lows : The lower four to six feet is a massive dove-colored, coarsely crystal- 

 line limestone. The next one to two feet consists of thin bedded dense 

 light blue limestone interbedded with coarsely crystalline layers which are 

 fossiliferous. Upon this lies a massive coarsely crystalline bed having a 

 thickness of four feet and containing few fossils. The upiier fifteen to 

 eighteen f(>et is made up of thin b(>ds of dense unfossiliferous calcareous 

 layers interbedded with coarsely crystalline limestone two to three inches 

 thick and containing abundance of fossils. Seams of shale separate the 

 ntimerous layers. 



The total thickness of the forma lion v.iries from twenty-five to twenty- 

 eight feet, it outcrops in narrow irregulai' lielts about the areas of the Mur- 

 freesboro limestone, and it is easily recognized by the great abundance of 

 f(tssils of which there is ;i predominance of bryo/oa. The following forms 

 are characteristic and abundant : MiholsoiKlhi /jiiJclini. \. fntmlifcra, 

 Annlotichia cxplanofii. ^<tictoi>onlhi crilirilimi. 



The Pierce limestone apparently lies coiiforin;ilily upon the ^lurfreesboro 



iGeol. Tenn. (1869). p. 2r.'.t. 

 »Blpin. Geol. Tenii. (liiooi. 

 »Geol. Tenn. (1869), p. liCl. 



