GROUND WATER IN NORTH-CENTRAL TENNESSEE

STRATIGRAPHY 35
Warsaw and the overlying St. Louis limestone, although the detailed
stratigraphic relations are not known.
The Warsaw formation is highly fossiliferous, especially in its
central and upper parts, although the remains are usually fragmental
and are difficult to classify because they generally decompose as
rapidly as the inclosing rock. Butts, in Overton County, recognized
Tricoelocrinus woodmani or a closely related form, Productus magnus,
Spirifer subequalis (common), Spirifer tenuicostatus, Spiriferetta
neglecta, Brachythyris subcardiformis, and Worthenopora spinosa.
Mather, 51 in eastern Sumner County, differentiated not far below the
top of the formation a key bed that is thickly crowded with fragments
of Spirifer washingtonensis. The lower part of the formation, how­
ever, resembles the underlying Fort Payne formation so much that
at many localities the two are not readily separable.
The Warsaw formation, which is about 100 feet thick, crops out
on the Highland Rim plateau in eastern Sumner County and forms
a broad belt along the higher slopes of the stream valleys farther
west. Like the overlying St. Louis limestone, it weathers on all the
upland tracts to a brick-red clayey soil containing many fragments of
chert, and unweathered rock crops out only in the stream valleys.
The sandstone beds that constitute the upper third of the Warsaw
formation in Overton County may be water-bearing farther west
where they pass beneath the St. Louis limestone, although they have
not been noted in the records of the few wells that have been drilled
to or below their horizon within the region of this investigation.
Furthermore, these sandstone beds are not well developed or are
entirely absent in the western part of the region, so that their value
as a source of water remains problematic. Even if the beds persisted
toward the west they probably would yield only saline water of high
concentration where they were deeply buried.
FORT PAYNE FORMATION
The Warsaw formation is underlain, with seeming conformity, by
the Fort Payne formation, an exceedingly heterogeneous and variable
assemblage of siliceous and calcareous shale and sandy, cherty, and
earthy limestone. In Stewart County, in the northwestern part of
the region, the upper part of the Fort Payne formation is very thick
bedded and consists of alternating bands of dense dark bluish-gray
limestone and persistent bands of dense dark-colored chert from 1 inch
to 1 foot or more in thickness. (See pi. 6, (7.) Throughout the region
the topmost beds of the formation are generally cherty, although
toward the .east and south this cherty facies thins noticeably and the
limestone becomes more earthy. In Cheatham County the greater
« Mather, K. F., Oil and gas resources of the northeastern part of Sumner County, Tenn.: Tennessee
Oeol. Survey Bull. 24, (Ann. Kept, for 1919, pt. 2-B), p. 25,1920.