GROUND WATER IN NORTH-CENTRAL TENNESSEE

SURFACE FEATURES OF CENTRAL TENNESSEE 19
tral and western Tennessee as they have reconstructed the surface are
from 2,200 fco 1,000 feet above sea level. 21 The highest remnants
occur along two intersecting axes of uplift which trend N. 20° E. near
Chattanooga and N. 40°-60° E. near McMinnville. The lowest rem­
nants are near the western limb of the Tennessee River. (See pi. 1.)
Shaw,22 on the other hand, has expressed a belief that all peneplains
of which remnants exist to-day in the Appalachian Plateaus province
are younger than the floor on which the Cretaceous rests and younger
than the unconformity at the top of the Cretaceous. He implies that
the Cumberland peneplain is probably not older than mid-Tertiary.
mOBOLAND RIM CYCUB
The gently undulating plain that is defined by the interstream
tracts of the Highland Rim plateau and formerly extended entirely
across the Nashville Basin is clearly a product of subaerial erosion,
inasmuch as it bevels warped Mississippian limestones. It is in fact
an extensive terrace or peneplain, formed by the erosion from the
former Cumberland Plateau «of a wedge-shaped mass of rock whose
base, from 700 to 850 feet high, is the Cumberland escarpment and
whose apex coincides approximately with the western limb of the
Tennessee River. The rock waste produced by this erosion was trans­
ported westward by streams and deposited as a series of coastal plain
sediments in the northern lobe of the Gulf of Mexico, which at that
time extended northward into southern Illinois and eastward within
approximately 10 miles of the present site of the Tennessee River.
Hayes and Campbell 23 conclude from the character of the coastal-
plain sediments that the beginning of the Highland Rim erosion cycle
is represented;by the Ripley formation (late Upper iCretaceous) and
that planation was essentially complete at the time of deposition
of the upper beds of the Vicksburg group (middle and early upper
Oligocene 24). Shaw, 25 however, tentatively correlates the Highland
Rim peneplain with the sub-Pliocene or possibly the sub-Miocene
unconformity in southern Mississippi. At the culmination of the
cycle the peneplain was a featureless surface, probably drained by
meandering streams with low gradient and with little capacity for the
transportation of land waste. Lusk 26 concludes that the meander
belt of the Cumberland River at the culmination of the Highland Rim
M Hayes, O. W., and Campbell, M. E., op. cit., pi. 6.
M Shaw, E. W., Ages of peneplains of the Appalachian province: Geol. Soc. America Bull., vol. 29, p.
686,1018.
« Hayes, C. W., and Campbell, M. E., op. cit., pp. 124-126.
w Cooke, C. W., The correlation of the Victoburg group: IT. 8. Geol. Survey Prof. Paper 133, pp. 1-10,
1923. Vaughan, T. W., Criteria and status of correlation and classification of Tertiary deposits: Geol.
Soc. America Bull., vol. 35, No. 4, pp. 727-730,1924.
M Shaw, E. W., Pliocene history*of»OTthern,aad£entralMissigsiopi^U. 8. Geol.-Survey Prof. Paper 108,
p. 163,1918.
» Lusk, B. G., Gravel on the Highland Rim plateau and terraces in the valley of Cumberland River;
Jour. Geology, vol. 36, No. 4, p. 166,1928.