GROUND WATER IN NORTH-CENTRAL TENNESSEE
GROUND WATER IN NORTH-CENTRAL TENNESSEE
GROUND WATER IN NORTH-CENTRAL TENNESSEE
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STRATIGRAPHY 45<br />
by Foerste,87 Pate and Bassler,88 and Miser.89 This section comprises<br />
rocks of Cayuga, Niagara, and Albion age. The rocks of Cayuga<br />
&ge constitute the Decatur limestone; those of Niagara age are divided<br />
into the Lobelville, Bob, Beech River, Dixon, Lego, Waldron, Laurel,<br />
and Osgood formations; and those of Albion age are the Brassfield<br />
limestone. These formations, whose general characteristics are given<br />
in the stratigraphic section (p. 27), constitute a somewhat variegated<br />
stratigraphic unit, which is 233^ feet thick at Clifton, Wayne County.90<br />
The Silurian rocks thin northward and eastward along the flank of<br />
the Nashville dome and finally wedge out in Macon County, slightly<br />
«ast of the area represented by Plate 4. According to Miser,91 this<br />
thinning is due to post-Silurian erosion that truncated the section<br />
at the top and is not primarily due to overlap, the only overlapping<br />
unit in the Silurian being possibly the Lobelville formation. The<br />
detailed stratigraphy of the Silurian rocks has been untangled at<br />
only a few places in north-central Tennessee, so that full discussion<br />
is not possible at this time.<br />
As shown by Plate 4, the Silurian rocks crop out in north-central<br />
Tennessee along the base of the Highland Rim escarpment and its<br />
outliers in Williamson, Cheatham, Davidson, and Sunnier Counties.<br />
According to Foerste 92 a rather full sequence of these rocks is also<br />
exposed in the Wells Creek Basin of southeastern Stewart County.<br />
ORDOVICIAN SYSTEM<br />
GENERAL FEATURES<br />
The Ordovician system of north-central Tennessee includes rocks<br />
of Upper, Middle, and Lower Ordovician age, the top of the system<br />
being placed at the top of the Richmond group. In this region the<br />
Brassfield limestone, of Albion age, rests disconformably on the Fern-<br />
vale formation (of early Richmond age, according to Ulrich), and the<br />
underlying Arnheim limestone, which is the basal formation of the<br />
typical Richmond group of Indiana, rests unconformably on the<br />
Leipers limestone (of early Maysville age, according to Ulrich).<br />
The stratigraphic break at the base of the Richmond group is con<br />
sidered by Ulrich and Bassler to be of considerable magnitude and<br />
greater than the break at its top, the formations with which the<br />
8' Foerste, A. F., Silurian and Devonian limestones of Tennessee and Kentucky: Qeol. Soc. America<br />
Bull., vol. 12, pp. 395-444,1901; Silurian and Devonian limestones of western Tennessee: Jour. Geology,<br />
vol. 11, pp. 554-583, 679-715,1903.<br />
88 Pate, W. F., and Bassler, E. S., The late Niagaran strata of west Tennessee: U. S. Nat. Mas. Proc.,<br />
vol. 34, pp. 407-432, 1908.<br />
» Miser, H. D., Mineral resources of the Waynesboro quadrangle, Tenn.: Tennessee Geol. Survey Bull.<br />
26, pp. 18-22, 1921.<br />
'« Pate, W. F., and Bassler, R. S., op. cit., pp. 411-412.<br />
" Miser, H. D., op. cit., pp. 18-22; also personal communication.<br />
*> Foerste, A. F., Silurian and Devonian limestones of western Tennessee: Jour. Geology, vol. 11, pp.<br />
690-694,1903.