265 
circular outcrop, but they confused the Murfreesboro and Ridley limestones 
at this time. 
The Murfreesboro limestone is the oldest formation exposed on the Nash- 
ville dome and outcrops only in Rutherford County upon the crests of 
secondary upfolds that occur along the valleys of Stones River and its 
tributaries. Thus, instead of a single area in which the formation appears 
at the surface, there are numerous small and isolated localities. 
The beds consist of thick layers of bluish gray, dense, bituminous lime- 
stones with much disseminated chert which appears upon weathered sur- 
faces in small irregular masses. At Lascassas, Rutherford County, the 
lower fifteen feet of the twenty-seven feet exposed consists of sandy, lam- 
inated, ripple-marked and sun-cracked limestone, which is evidence that 
the sea was shallow and the shore line probably not far distant during the 
closing stage of the deposition of the Murfreesboro limestone. 
Fossils are few and difficult to obtain from the unweathered 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, 
silicified specimens occur in considerable abundance. Some of the best 
localities are near the Central Normal School, at Murfreesboro, and upon 
the bluffs of Stones River near the Nashville pike. Salterella_ billingst, 
Lophospira perangulata, Liospira abrupta, Helicotoma tennesseensis, H. 
declivis are the most abundant species and are characteristics of the forma- 
tion. 
The maximum exposure of this limestone is seventy feet, with the basal 
beds not exposed. 
Pierce limestone. This formation was named by Safford: in 1869, 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 haying a 
thickness of four feet and containing few fossils. The upper fifteen to 
eighteen feet is made up of thin beds 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 
numerous layers. 
The total thickness of the formation yaries from twenty-five to twenty- 
eight feet, it outcrops in narrow irregular belts about the areas of the Mur- 
freesboro limestone, and it is easily recognized by the great abundance of 
fossils of which there is a predominance of bryozoa. The following forms 
are characteristic and abundant: Nicholsonella pulchra, N. frondifera, 
Anolotichia explanata, Stictoporella cribrilina. 
The Pierce limestone apparently lies conformably upon the Murfreesboro 
1Geol. Tenn. (1869), p. 259. 
2Elem. Geol. Tenn. (1900). 
1Geol. Tenn. (1869), p. 261. 
