GROUND WATER IN NORTH-CENTRAL TENNESSEE

GROUND WATEB IN NORTH-CENTRA!, TENNESSEE 177
RUTHERFORD COUNTY
[Area, 614 square miles. Population, 32,286]
GENERAL FEATURES
Rutherford County lies in the southeast corner of the region
described in this report (pi. 1), approximately at the geographic
center of the State. Its county seat and principal town, Murfrees-
boro, has a population of 7,993.
The county occupies the southeastern part of the northern lobe of
the Nashville Basin (p. 18) and is roughly a natural physiographic
unit in that its eastern, southern, and western boundaries follow
approximately the divide surrounding the basin of the Stone River.
Extensive tracts in its central and western parts lie on the Nashville
Basin peneplain (pp. 20-22), a nearly featureless plain that slopes
northwestward and is from 550 to 700 feet above sea level. On this
plain sink holes, undrained depressions, and "glades" essentially
flat areas of limestone with little or no soil are numerous. This
plain is surrounded by a nearly continuous belt of hills along the
boundaries of the county, the hilly terrane being a product of a mature
dissection of outlying remnants of the Highland Rim plateau. The
largest of these remnants is a branching ridge about 4 miles long near
the southeast corner of the county. Its summit, 1,352 feet above sea
level, is the highest point in the county and in the entire region covered
by this report.
The county is drained northwestward by the Stone River, whose
principal branches occupy trenches cut 25 to 100 feet below the Nash­
ville Basin peneplain. Many extensive tracts on this peneplain,
however, have no surface drains, and their run-off is carried by solution
conduits, which discharge as perennial springs. The larger of these
subsurface drains are adjusted to the surface streams.
Rutherford County lies on the apex of the Nashville dome (pp. 62-63),
the rock strata dipping radially away from a point near Fosterville,
south of Murfreesboro. Hence the oldest rocks exposed by that dome,
of Lower Ordovician age, crop out in the central part of the county
and are surrounded by concentric bands of the younger formations.
The youngest strata exposed in the county, which belong to the lower
part of the Fort Payne formation, include earthy cherty limestone
and sandy shale; they cap several of the highest ridges in the south­
eastern and southwestern parts of the county. These beds are under­
lain by the Chattanooga shale, which is generally accompanied at its
base by the Hardin sandstone member. This shale is underlain
unconformably by rocks of Ordovician age, the Devonian and Silurian
systems and the upper part of the Ordovician system being absent.
The rocks of Upper Ordovician age that are present are the Leipers
limestone. Those of Middle Ordovician age are, from the top down-