GROUND WATER IN NORTH-CENTRAL TENNESSEE

GBOUND WATEB IN NOETH-CENTEAL TENNESSEE 153
HUMPHREYS COUNTY
[Area, 461 square miles. Population, 12,039]
GENERAL FEATURES
Humphreys County, which adjoins Houston County on the south,
occupies the southwest corner of the region covered by this report
(pi. 1) and embraces the greater part of the most sparsely populated
area in north-central Tennessee. Waverly and McEwen, with
populations of 1,152 and 620, respectively, are its two largest towns;
Waverly is also the seat of the county government.
Humphreys County lies wholly within the Highland Rim plateau
(pp. 16-18), and extensive tracts along the divide between the Tennes­
see and Cumberland Rivers in its eastern part present the gently
undulating plain characteristic of that physiographic feature. In
this part of the county the plain attains a maximum altitude of
about 825 feet above sea level. Toward the west, however, the
interstream tracts that represent portions of the once continuous
plateau become somewhat lower and are about 675 to 725 feet above
sea level near the Tennessee River. The western part of the county
is deeply and intricately dissected by the Tennessee and Duck Rivers
and their subparallel tributaries, which head in mature valleys cor­
relative with the Nashville Basin peneplain and in their lower reaches
occupy youthful trenches imperfectly adjusted to the present stage
of stream erosion. The relief in this part of the county is of the order
of 400 feet.
The consolidated rocks exposed in Humphreys County are of
Mississippian, Devonian, and possibly Silurian age and in general
dip nearly westward about 10 to 15 feet to the mile. The youngest
or uppermost of these rocks are the massive subcrystalline beds of
the St. Louis limestone and Warsaw formation, which cap all the
interstream plateau tracts. The underlying Fort Payne formation
comprises in this county thin beds of dense and extremely cherty
limestone; it forms the valley slopes of the larger streams and of the
lower reaches of the tributaries. Neither the New Providence shale
nor the Ridgetop shale, which appear in the complete stratigraphic
section (pp. 26-29), is known to be present within the county, and the
Fort Payne formation rests directly upon the Chattanooga shale.
Although the Tennessee, Duck, and Buffalo Rivers have cut down to
the approximate horizon of the Chattanooga shale throughout the
county, it is known to crop out only in a few small separated areas.
It is possible, however, that this shale crops out much more exten­
sively in the county than these discontinuous areas indicate. The
Pegram limestone, of upper Middle Devonian age, is not known in
Humphreys County, but the underlying Camden chert, also of Middle
Devonian age, crops out directly beneath the Chattanooga shale
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