GROUND WATER IN NORTH-CENTRAL TENNESSEE
GROUND WATER IN NORTH-CENTRAL TENNESSEE
GROUND WATER IN NORTH-CENTRAL TENNESSEE
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STRATIGRAPHY 49<br />
Locally the basal member is a rather massive coarsely crystalline<br />
limestone which incloses masses of Stromatocerium pustulosum from 3<br />
inches to 3 feet in diameter. At some places this Stromatocerium-<br />
bearing bed is replaced, at least in part, by siliceous shale which is<br />
filled with portions of the sponge Pattersonia aurita and corals of the<br />
genus Columnaria. Elsewhere the basal member resembles the granu<br />
lar beds of the underlying Bigby limestone and, in common with that<br />
formation, contains Rqfinesquina, alternata in abundance, although<br />
always in association with characteristic Catheys Bryozoa, such as<br />
Heterotrypa parvulipora. The lower half of the Catheys formation<br />
also contains corals of the genera Streptelasma and Tetradium, which,<br />
with the Stromatocerium and Columnaria to which reference has been<br />
made, are recurrent in the overlying Leipers formation, as is pointed<br />
out by Ulrich.99 The Catheys fauna is of late Middle Ordovician<br />
(upper Trenton) age.<br />
The Catheys limestone crops out over extensive areas of medium<br />
altitude in eastern Williamson County and in southern Davidson and<br />
Sumner Counties. It also crops out on the upper slopes and tops of<br />
the higher ridges in eastern Wilson County and along the east, south,<br />
and west sides of Rutherford County. (See pi. 4.) The Catheys<br />
fauna has not been recognized in the Wells Creek Basin of Stewart<br />
County.<br />
CANNON LIMESTONE<br />
The Cannon limestone was originally defined by Ulrich * as including<br />
all the strata that lie below the Chattanooga shale and above the<br />
Hermitage formation on the east side of the Nashville dome, the type<br />
region being Cannon County. As thus defined, the formation com<br />
prises an upper portion whose maximum thickness is about 100 feet<br />
and a lower portion 150 to 200 feet thick. The upper portion contains<br />
a Catheys fauna and is the eastward extension of the typical Catheys<br />
limestone. The lower portion consists for the most part of massive<br />
gray limestone, some beds of which are granular and others knotty<br />
and earthy; many of the strata are highly fossiliferous.2 This lower<br />
portion is equivalent to the Perryville, Flannagan, and Bigby forma<br />
tions o£ Kentucky, though the typical Bigby limestone is wholly or<br />
in part missing in and about Cannon County.<br />
Later Ulrich 3 redefined the Camion limestone by excluding the<br />
Catheys limestone at the top and the Bigby limestone at the bottom,<br />
so that the term might be applied to the strata on both the east and<br />
west flanks of the Nashville dome. The redefined formation includes<br />
M Ulrich, E. O., op. cit., pp. 299-300.<br />
»Idem, pp. 417-418,429.<br />
1 Galloway, J. J., Geology and natural resources of Rutherford County, Tenn.: Tennessee Geol. Survey<br />
Bull. 22, p. 53,1919.<br />
* Ulrich, E. O., in Secrist, M. H., The zinc deposits of east Tennessee: Tennessee Dept. Education Div.<br />
Geology Bull. 31, p. 16,1924.