GROUND WATER IN NORTH-CENTRAL TENNESSEE

44 GROUND WATER IN NORTH-CENTRAL TENNESSEE
LOWER DEVONIAN SERIES
Rocks of Lower Devonian age are known at two localities in the
Wells Creek Basin, Stewart Comity, but have not been identified
elsewhere in north-central Tennessee.
HARRIMAN (?) CHERT
At one of these localities, in the south bank of the Cumberland
River about 1 mile southwest of Cumberland City, white, gray, and
buff cherty limestone as much as 40 feet thick crops out above the
Birdsong limestone. It is generally very poorly exposed. Foerste 82
has suggested that this cherty limestone may be correlative with the
Camden chert, of Middle Devonian age, but Dunbar M has correlated
it provisionally with the Harriman chert, of Lower Devonian (Oris-
kany) age, on the basis of a single valve of Spirifer murchisoni?.
The detailed stratigraphic relations and area! extent of the Harri­
man formation in north-central Tennessee are not known.
BIRDSONG LIMESTONE
At the other locality of Lower Devonian rocks, which is at the top
of a section in a railroad cut about 3 miles southwest of Cumberland
City, Foerste 84 has identified limestone of the Linden group, of
Helderberg age. Dunbar 85 has correlated this limestone with the
Birdsong shale, and Bucher 86 has recognized in it such Helderberg
fossils as Atrypa reticularis, Leptostrophia beckii, a small Delthyris,
and Meristella. According to Dunbar, the formation overlaps east­
ward upon the Silurian rocks and is generally absent by erosion east
of the Tennessee River. In the Wells Creek Basin it is represented
by 10 to 20 feet of thin-bedded and somewhat cherty limestone,
which is not commonly well exposed. The areal extent of this strati-
graphic unit in north-central Tennessee has not been traced.
SILURIAN SYSTEM
The rocks of Silurian age that crop out on the Western and north­
western flanks of the Nashville dome (see pp. 62-63) in Tennessee
constitute a classic section which has long been a field of paleonto-
logic and stratigraphic study and which has been studied in detail
«8 Foerste, A. F., Silurian and Devonian limestones of western Tennessee: Jour. Geology, vol. 11, p. 693,
1903.
M Dunbar, C. O., op. cit., p. 74.
M Foerste, A. F., op. cit. (1903), pp. 690-692.
M Dunbar, C. O., op. cit., p. 58.
* Bucher, W. H., The stratigraphy, structure, and origin of Wells Creek Basin, Tenn.: Tennessee Dept.
Education Div. Geology [in preparation].