GROUND WATER IN NORTH-CENTRAL TENNESSEE
GROUND WATER IN NORTH-CENTRAL TENNESSEE
GROUND WATER IN NORTH-CENTRAL TENNESSEE
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132 <strong>GROUND</strong> <strong>WATER</strong> <strong>IN</strong> <strong>NORTH</strong>-<strong>CENTRAL</strong> <strong>TENNESSEE</strong><br />
Davidson County lies on the northwest flank of the Nashville dome<br />
(see pp. 62-63), so that at any particular altitude successively older<br />
strata appear toward the southeast. The exposed rocks constitute<br />
nearly a full section from the St. Louis limestone, of Mississippian<br />
age, down to the Kidley limestone, of Lower Ordovician age. (See<br />
pp. 33-55.) The massive subcrystalline St. Louis limestone crops<br />
out only in the Highland Kirn plateau northwestward from Joelton,<br />
where it is overlain by a thick mantle of cherty residual soil. The<br />
underlying Fort Payne formation, which in this county is generally<br />
thin-bedded earthy cherty limestone, crops out in all the upper slopes<br />
of the Highland Rim escarpment and forms the divide between the<br />
Cumberland and Harpeth Rivers. The New Providence and Ridge-<br />
top shales, which are stratigraphically beneath the Fort Payne<br />
formation, crop out in an area several miles across northwest of<br />
Nashville but are not widespread elsewhere. The Chattanooga shale<br />
crops out as a narrow band following the lower slope of the Highland<br />
Rim escarpment and inclosing erosion outliers of the plateau as far<br />
east as Nashville. Heavy-bedded dense and crystalline limestones<br />
of Devonian and Silurian age crop out along the base of the escarp<br />
ment and of the outliers of the plateau and in the valley of the Harpeth<br />
River below Belleview. The stratigraphic relations of the formations<br />
of these two systems, which lap eastward over the underlying strata,<br />
have not been traced in detail. The earthy and dense pure limestones<br />
of Upper and Middle Ordovician age cover most of the rolling terrane<br />
of the Nashville Basin north and west of Nashville. The massive<br />
compact Carters limestone member of the Lowville limestone is exposed<br />
by the Cumberland River in the southeastern part of Nashville and<br />
crops out extensively farther southeast. The Lebanon and Ridley<br />
limestones of the Stones River group appear successively in the lower<br />
parts of the county and cover larger and larger areas toward the<br />
southeast. The areas within which the several stratigraphic units<br />
crop out are shown on Plate 4.<br />
<strong>GROUND</strong>-<strong>WATER</strong> CONDITIONS<br />
The water-bearing properties of the rocks in Davidson County dif<br />
fer greatly from place to place and for the most part can not be fore<br />
told from stratigraphic position alone. Rather, the ability of any<br />
particular stratum to transmit water is generally limited by the number<br />
and size of solution channels and hence is dependent upon the solu<br />
bility of the rock, the number and persistence of joints, and the posi<br />
tion of the stratum with relation to present and past equilibrium<br />
profiles of underground drainage. (See pp. 78-82.) Thus in several<br />
parts of the county a water-bearing zone occurs in the limestone at<br />
about the same depth below the surface even though at different<br />
stratigraphic horizons. On the other hand, a few of the formations