GROUND WATER IN NORTH-CENTRAL TENNESSEE

STRATIGRAPHY 25
In general the occurrence of ground water in any region depends
in some measure upon the texture of the rocks, so that the stratig­
raphy is a guide to the development of ground-water supplies. Hence
the stratigraphy of north-central Tennessee is here discussed in some
detail. However, few of the stratigraphic units have a distinctive
lithology over any large portion of the area, so that identification of
the beds must rest upon the contained fossils, and it is difficult to
apply in practice the relations between stratigraphy and occurrence
of ground water.
The stratigraphic sequence and general lithologic character of the
rocks are summarized in the following table, and each of the strati-
graphic units is described in the succeeding pages. The sequence of
description, however, is the inverse of that which is usually followed
in geologic reports, in that the formations are described from the top
of the geologic column downward that is, in the order in which they
are encountered by the driller.
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