GROUND WATER IN NORTH-CENTRAL TENNESSEE

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