GROUND WATER IN NORTH-CENTRAL TENNESSEE

StJBFACE FEATURES OF CENTRAL TENNESSEE 17
the entire central portion of the State, from the Cumberland escarp­
ment on the east almost to the Tennessee River on the west. It
extends northward beyond the limits of this survey entirely across
Kentucky and coincides with the Lexington Plain of that State.
Southward it extends into Alabama, where it comes to an indefinite
terminus. In Tennessee the plateau attains its maximum altitude,
about 1,365 feet above sea level, in an outlying remnant near the
southeast corner of Rutherford County, about 1 mile west of the junc­
tion of that county with Cannon and Coffee Counties. Thence it
descends radially northward and westward, with a nearly uniform
gradient. Its altitude in northeastern Sumner County is about 950
feet above sea level, in northwestern Stewart County about 575 feet,
and in west-central Humphreys County about 725 feet. Hayes and
Campbell w have likened the contour of the restored plain to that of
an inverted spoon whose major axis trends N. 40°-60° E. and passes
through the city of McMinnville, about 25 miles east of Rutherford
County.
The interstream tracts of the plateau are veined by ephemeral
drainageways which have very flat longitudinal and transverse pro­
files and usually show a local relief of less than 50 feet. At some
localities bowl-shaped or spoon-shaped depressions without surface
drainage dot the otherwise featureless plain. (See pi. 2, B.} The
largest of these depressions or "sinks" are as much as a mile in diame­
ter and 40 feet deep. They are most numerous in the tracts that lie
between two converging major streamways, in the vicinity of the
point of confluence.
The northern part of the plateau is trenched to a depth of 250 to
600 feet in two well-defined stages by the Cumberland River, whose
ingrown meanders 19 swing laterally between 2 and 7 miles. Its larger
tributaries also meander, and all occupy deep and narrow valleys
which steepen abruptly at their heads. Along its common boundary
with the Nashville Basin the plateau is deeply trenched by many
subparallel drains several miles long and disintegrates into a maze of
flat-topped linear ridges and outliers, as well as remnants that have
been somewhat reduced by erosion. Hence the so-called Highland
Rim escarpment, which separates plateau and basin, is by no means
a linear feature. Its position as plotted on Plate 1 is generalized to
delineate that area which is more the dissected plateau from the typi­
cal basin and is drawn tangent to the prominent headlands of the
plateau. Outstanding among the outlying remnants of the plateau
is the chain of hills that extends across southern Rutherford County
» Hayes, O. W., and Campbell, M. B., Qeomorphology of the southern Appalachians: Nat. Oeog. Mag.,
vol. 6, pi. 6, 1894.
19 Meanders that are formed or accentuated by lateral shift coincident with downcutting. For original
definition see Rich, J. L., Certain types of stream valleys and their meaning: Jour. Geology, vol. 22, p.
470,1914.