IfeEL.] TENNESSEE. 305 
»ddle Tennessee have been divided. The "succession of the various 
bds, and of the faunas characterizing each, is exactly the same in 
he two areas, so that there can be little or no doubt respecting the 
hntinuity of the beds beneath the later rocks making the interven- 
ig Cumberland Plateau. 
ORDOVICIAN LIMESTONES OF MIDDLE TENNESSEE. 
L'nm'Htoncs of the Stones tt'n y < /• group. — The nearly horizontal lime- 
Snes of this group form the. floor of the basin, the lowest formation 
itcropping at Murfreesboro. They are all essentially nonmagnesian, 
id hence deserve mention as possible or promising materials. The 
urfreesboro limestone, with an exposed thickness of 70 feet, is light 
ue, usually heav} 7 bedded, occasionally rather earthy, and often very 
ert v. Murfreesboro is situated near the center of the area in which 
is limestone conies to the surface. The diameter of the area, which 
eludes, also, small outliers of later formations, ranges from 12 to 14 
iles. 
The Fierce limestone, having a maximum thickness of scarcely 30 
et, rests on the Murfreesboro limestone and forms a narrow belt 
bund the outcrops of that formation. It consists chief! y of thin 
vers of highly fossiliferous pure or somewhat argillaceous limestone 
terbedded with thin seams of calcareous shale. 
The next formation, the Ridley limestone, having a thickness of from 
to 100 feet, consists of thick- bedded, light-blue, sparsely cherty 
nestone. The Ridley, like the Pierce, outcrops in an irregular cir- 
lar band around the Murfreesboro area. Limited exposures of its 
>per beds occur also in Bedford and Marshall counties. 
The Lebanon limestone has lithologic characters similar to those of 
e Pierce limestone. It is the fourth formation from the base of the 
ones River group, has a thickness of 100 feet or more, and occupies 
arger area than the preceding limestones. The towns of Lebanon, 
swisburg, Shelbyville, La Vergne, and Fosterville are located on 
is limestone. It is shown also in the bluffs 'of Duck River at Colum- 
A considerable proportion of the bed consists of argillaceous 
lestone. 
The Carter limestone, the uppermost division of the Stones River 
oup, is a very light blue, compact, heavy-bedded limestone, 40 to 80 
it thick. It occurs in all of the counties in the central basin, and is 
)re often burned for lime than any other of the Ordovician limestones 
the basin. 
Trenton group. — The Trenton limestones, including the Hermitage, 
jgby, and Cathej^s limestones, as defined in the Columbia folio, a form 
■wide but irregular belt, completely encircling the central Stones 
■ver limestone areas of the basin. 
Bull. 243—05 20 
