GROUND WATER IN NORTH-CENTRAL TENNESSEE

20 GROUND WATER IN NORTH-CENTRAL TENNESSEE
cycle, for example, was aboufc a mile less than the present swing of the
meanders. Evidently this condition of erosional stagnation persisted
for a considerable interval, during which the surface was lowered
principally by solution of the limestone, and a mantle of residual clay
and fragmentary chert, now preserved upon the upland tracts, was
accumulated to a thickness of 90 feet or more. Even during the
final stages of the planation, however, stream erosion probably con­
tinued actively along the Cumberland escarpment, for Lusk 27 notes
the occurrence on the Highland Eim plateau near Celina, Clay County,
of waterworn gravel whose particles are similar to pebbles of the
Pennsylvanian conglomerates exposed in the escarpment. The gravel
is presumably stream-borne. Hayes and Ulrich 28 describe deposits
of coarse stream gravel on the plateau in the Columbia quadrangle,
west of the Nashville Basin, although it is possible that these deposits
represent the Tuscaloosa formation (see pp. 31-33), of late Upper
Cretaceous age. The Highland Eim erosion cycle was brought to
an end by renewed crustal warping and uplift accompanied by re­
juvenation of the streams.
NASHVILLE BASIN CYCLE
GENERAL FEATURES
According to Hayes and Campbell 29 the rejuvenation that termi­
nated the Highland Eim cycle was caused by renewed regional uplift
and arching of the strata about an axis striking N. 40°-60° E. through
McMinnville. At its culmination this crustal activity had elevated
the Highland Eim peneplain to its present altitude, although the
movement very probably occurred in several stages. Marked re­
cession of the Mexican Gulf resulted. The major streams became
intrenched upon the new-born upland but were forced to cut entirely
new lower courses in pace with the marine recession. These lower
courses were probably controlled chiefly by the form of the warped
surface, though it is likely that stream capture and unequal rates of
erosion were secondary factors in sculpture of the land surface. Thus
the resultant courses of the Tennessee and Cumberland Eivers were
established westward and northward away from the direct route to
the Gulf.30
» Lusk, E. O., op. cit., pp. 164-170.
» Hayes, C. W., and Ulrich, E. O., U. S. Oeol. Survey Geol. Atlas, Columbia folio (No. 95), p. 1,1903.
» Hayes, C. W., and Campbell, M. K., op. cit., p. 119, pi. 6.
w Hayes, C. W., and Campbell, M. E., Qeomorphology of the southern Appalachians: Nat. Qeog. Mag.,
vol. 6, pp. 105-120,1895. Hayes, C. W., Physiography of the Chattanooga district, in Tennessee, Georgia,
and Alabama: U. S. Oeol. Survey Nineteenth Ann. Kept., pt. 2, pp. 1-58, 1899. Simpson, C. T., The
evidence of the Unionidae regarding the former courses of the Tennessee and other southern rivers: Science,
new ser., vol. 12, pp. 133-136,1900. White, C. H., The Appalachian Eiver versus a Tertiary trans-Appa-
lachian river in eastern Tennessee: Jour. Geology, vol. 12, pp. 34-39,1904. Johnson, D. W., The Tertiary
history of the Tennessee River: Jour. Geology, vol. 13, pp. 194-231,1905. Adams, G. I., The course of the
Tennessee Biver and the physiography of the southern Appalachian region: Jour. Geology, vol. 36, pp.
481-493, 1928.