GROUND WATER IN NORTH-CENTRAL TENNESSEE
GROUND WATER IN NORTH-CENTRAL TENNESSEE
GROUND WATER IN NORTH-CENTRAL TENNESSEE
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WJfetlAMSON<br />
i&entf&nts, also in thfe middle of upper part of the hill slopes farther<br />
feast. It rests unoonformably upon rocks that range in age from<br />
lower middle Silurian to Middle Ordoviciah, the jpre-Chattanooga<br />
Devonian rocks being absent in all parts of the county and the Silurian<br />
and Upper Ordovician being absent east of Franklin. In a few<br />
places particularly in the valleys of tributaries of Leipers Creek, a<br />
branch of the Duck River, near fche soufchwesfc corner of fche county;<br />
in fche valley of the South Harpeth River near thfc northern boundary<br />
6f the county; also between the West Harpeth River and Murphy<br />
Fork about 2% miles east-southeast of Hillsboro fche Chattanooga<br />
shale rests upon the Osgood limestone or possibly Upon younger beds<br />
of middle Silurian (Niagaran) age. In fche same localities the Chat<br />
tanooga shale, or the Osgood limestone where that formation is<br />
present, is underlain in turn by the soft green or chocolate-colored<br />
shale with associated bands of crystalline limestone and granular<br />
crysfcalline limes fcone fchat constitute fche Fernvale and Arnheim forma<br />
tions, of Richmond age. The Leipers formation, which in fchis<br />
county comprises knofcfcy earfchy limestone and shale or granular<br />
crystalline limestone without shale, crops out at its proper strafci-<br />
graphic horizon along fche base of fche Highland Rim escarpment,<br />
also in the lower and middle slopes of Sugar Ridge and of the hilly<br />
tract between Franklin and Brenfcwood. However, fche formation<br />
thins eastward, both by unconformity at its top and by overlap at its<br />
base, and is not known to crop out south and east of Franklin. The<br />
Leipers formation, or the Chattanooga shale where the Leipers is absent,<br />
rests upon knotty earfchy limestone and shale with associated thick beds<br />
of impure limestone. These beds, which constitute the Catheys forma<br />
tion, do not crop out anywhere in the county west of the Highland<br />
Rim escarpment. Together with the underlying massive Cannon<br />
limestone and the granular, crystalline, laminated Bigby limestone,<br />
the Catheys formation crops out on the lower slopes and aboufc fche<br />
flanks of fche hilly tracts of the eastern half of the county. Sfcrati-<br />
graphically beneath the Bigby limestone is the Hermitage formation,<br />
which in the central part of the county comprises sandy, granular,<br />
phosphatic limestone at the top and even-bedded shale and sandy<br />
limestone below, but which along the east edge of the county is largely<br />
thin-bedded sandy limes fcone. This formation crops out extensively<br />
along the flanks of the ridge that divides the Harpeth and West<br />
Harpeth Rivers in the central part of the county and on the middle<br />
and upper slopes of the hilly areas in the eastern part of the county.<br />
It is underlain successively by the massive compact cherty beds of the<br />
Lowville limestone and by the thin-bedded compact Lebanon lime<br />
stone, of which fche most extensive outcrop covers the floor and lower<br />
slopes of the Harpeth River Valley from the vicinity of Franklin<br />
eastward to and beyond tbe boundary of the county. The Lowville