GROUND WATER IN NORTH-CENTRAL TENNESSEE

STRATIGRAPHY 39
New Providence shale, the Ridgetop shale was deposited only in em-
bayments on the northern and western flanks of the Nashville dome,
according to Bassler.63 The basal Maury glauconitic member is an
extremely variable but persistent bed, which may be a green, blue-
black, or black shale, a brown sandy shale, or even a buff sandstone.
Its lower part is glauconitic at many places and generally contains
kidney-shaped phosphatic nodules. Swartz 64 has concluded that this
basal member is a lithologic but not a chronologic unit, that it was
deposited universally throughout the region and that it is separated
from the underlying Chattanooga shale by an unconformity that de­
creases from west to east and probably disappears between central
and eastern Tennessee.
The uppermost 20 feet of the Ridgetop shale at the type locality
and the earthy limestone member that occurs 62 feet below the top of
the formation are abundantly fossiliferous and contain numerous bryo-
zoans, ostracodes, and other genera of known Kinderhook age, as
noted by Bassler.68 The sandy shale and chert member whose top is
15 to 20 feet below the top of the formation contains such pseudo-De­
vonian fossils as Striatopora and Michelinia, but the presence of well-
developed species of Palaeads, Productus, and Agaricocrinus is
conclusive evidence of post-Devonian age. The Ridgetop shale is
the "fetid shale" of Safford, which Safford and Killebrew 66 and Hayes
and Ulrich 67 included with the overlying Fort Payne formation as
the so-called "Tullahoma limestone" or "Tullahoma formation."
At this horizon have been found many unnamed bryozoans and numer­
ous species of ostracodes, of which only one, Ctenobolbina loevlata
Ulrich, has been named. The other genera collected at this horizon
in Hickman and Maury Counties have been studied by Winchell,68
whose list of species follows:
Spirifera hirta? White and Whitfield.
Rhynchonella sageriana Winchell.
Chonetes multicosta Winchell.
Chonetes pulchella? Winchell.
Producta concentricata Hall.
Chonetes fischeri Norwood and
Pratten.
Zaphrentis ida? Winchell.
Conularia byblis White.
Leda bellistriata? Stevens.
Solen scalpriformis Winchell
Discina saffordi Winchell.
Pleurotomaria hickmanensis Winchell.
Phillipsia tennesseensis Winchell.
CARBONIFEROUS OB DEVONIAN SYSTEM
CHATTANOOGA SHAIE
The ubiquitous basal member of the Ridgetop shale is underlain
by the Chattanooga shale, which is known locally as the "black shale "
» Bassler, R. S., op. cit. (1911), pp. 220-222.
64 Swartz, J. H., op. cit., p. 29.
w Bassler, R. S., op.cit. (1911), pp. 217-218.
66 Safford, J. M., and Killebrew, J. B., op. cit., pp. 143-144.
" Hayes, O. W., and Ulrich, E. O., U. S. Qeol. Survey Oeol. Atlas, Columbia folio (No. 95), p. 3,1908.
« Winchell, Alexander, in Safford, J. M., Geology of Tennessee, pp. 442-446, Nashville, 1869.