GROUND WATER IN NORTH-CENTRAL TENNESSEE

38 GROUND WATER IN NORTH-CENTRAL TENNESSEE
brachiopods Rhipidomdla michelinia L'Eveille and Chonetes illinois-
ensis Norwood and Pratten. The species listed by Bassler are as
follows:
Favosites valmeyerensis Weller.
Beaumontia amerioana Weller.
Zaphrentis oliffordana Edwards and
Haime.
Amplexus rugosus Weller.
Amplexus brevis Weller.
Cladoconus americana Weller.
Monilopora crassa (McCoy).
Rhipidomella michelinia L'Eveille.
Chonetes illinoisensis Worthen.
Spirifer vernonensis Swallow.
Lasiocladia hindei Ulrioh.
Rhombopora incrassata Ulrioh.
Cystodictya pustulosa Ulrioh.
Fenestella regalis UMoh.
Ptilopora cylindraoea Ulrich.
Metichthyocrinus tiaraformis (Troost).
Barycrinus cornutus (Owen and Shumard).
Catillocrinus tennesseensis (Troost).
Halysiocrinus perplexus (Shumard).
Synbathocrinus robustus Shumard.
Schizoblastus decussatus (Shumard).
The New Providence shale is separated from the overlying Fort
Payne formation by a slight disconformity and was probably truncated
by erosion before the deposition of the younger beds. Furthermore,
Bassler 58 believes that the formation was not deposited widely over
the area but was limited to definite embayments that converge radi­
ally toward the Nashville dome. (See pp. 62-63.)
RIDGETOP SHALE
The Fort Payne formation, or the New Providence shale where
present, is underlain locally along the northern and western sides of
the Nashville dome by the Ridgetop shale, a formation of Kinder-
hookian age. The type section 69 of the formation, along the Louis­
ville & Nashville Railroad between Baker and Ridgetop, in Davidson
County, consists of light-blue to green clay that incloses several thin
beds of earthy sandstone, earthy limestone, and chert. The lowermost
bed of the section as defined by Bassler is characteristically a layer of
sandy chert about 1 foot thick. Miser 60 and Swartz,61 however, have
shown that the Maury green shale of Safford and Killebrew62 should be
included with the Ridgetop shale, although in some reports it has been
regarded as the upper member of the underlying Chattanooga shale.
The Ridgetop shale, including the Maury member, is 102 to 107 feet
thick at the type section, although at Whites Creek Spring, about 5
miles to the southwest, it is but 41 feet thick. Like the overlying
88 Bassler, K. S., The Waverlyan period of Tennessee: U. S. Nat. Mus. Proc., vol. 41, pp. 220-222, 1911;
Early Mississippian rocks of northern Tennessee [abstract]: Geol. Soc. America Bull., vol. 36, No. 1,
p. 221, 1925.
89 Bassler, R. S., The Waverlyan period of Tennessee: U. S. Nat. Mus. Proc., vol. 41, pp. 216-218,1911.
6° Miser, H. D., in Drake, N. F., Economic geology of the Waynesboro quadrangle: Resources of Ten­
nessee, vol. 4, p. 100, Tennessee Geol. Survey, 1914. Miser, H. D., Structure of the Waynesboro quadrangle
with special reference to oil and gas: Idem, vol. 7, p. 201,1917.
M Swartz, J. H., The age of the Chattanooga shale of Tennessee: Am. Jour. Sci., 5th ser., vol. 7, pp. 28-29,
1924.
92 Safford, J. M., and Killebrew, J. B., The elements of the geology of Tennessee, p. 141, Nashville, Foster
£ Webb, 1900.