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Alluvium (Qa) and Glacial Outwash Sediments (Qa)
Topography
These sediments form floodplains, valley bottoms, and terraces of the
Cumberland, Tennessee, and Mississippi Rivers and tributaries. Valley-train
deposits beneath terraces along Mississippi River.
Hydrology
These sediments yield several hundred gallons a minute to drilled wells
in the alluvium of the Tennessee River valley. They yield enough water
for a modern domestic supply (more than 500 gallons per day) to nearly all wells,
except in small valleys where the alluvium is thin and fine-grained.
Water ranges in hardness from 12 to 664 ppm and in dissolved solids
from 53 to 1,220 ppm. Iron may be present in objectionable amounts.
Loess
Topography
Forms a thin mantle over most upland and gently sloping sides of stream
valleys. Thick deposits adjacent to the Mississippi River thin to a
veneer near Kentucky Lake. Forms steep bluffs where thick. Many badlands
or heavily eroded gullies occur in the uplands.
Hydrology
Not an aquifer. Yields small amounts of water to a few wells. When saturated
by rainfall, transmits water to underlying aquifers.
Terrace Gravel Deposits and Continental Deposits (QTcl)
Topography
These deposits occur on uplands and eroded edges of uplands above 370
feet.
Hydrology
These deposits yield small quantities of water suitable for household
use. One spring had measured discharge of 47 gallons per minute. Most wells yield
less than 10 gallons per minute. Water-bearing gravel usually overlies clay or
indurated layers. Water ranges in hardness from 8 to 724 ppm and in
dissolved solids from 43 to 782 ppm. Iron content is generally low.
Jackson, Claiborne (Tjc), and Wilcox Formations (Tw)
Topography
These formations lie in uplands and high-level erosional surfaces over
most of county.
Hydrology
Sand yields enough water for domestic use near the outcrop area of Porters
Creek clay and in areas of perched water. Drilled wells penetrating
main zone of saturation where beds are thick yield as much as 1,700
gallons per minute. Hardness of water ranges from 7 to 212 ppm, and dissolved solids
from 28 to 431 ppm. Iron may be present in objectionable amounts.
Porters Creek Clay (Tp)
Topography
The Porters Creek crops out along Clarks River valley and in adjacent
uplands from Tennessee state line to Paducah.
Hydrology
The Porters Creek probably will yield a little water from joints and
from sandstone “dikes.” Water is probably hard and high in
iron. The formation is important as a confining layer.
Clayton and McNairy Formations (TKcm)
Topography
These formations create uplands and dissected ridges between Kentucky
Lake and Clarks River. In southeastern Marshall County, badlands are
formed where McNairy sand crops out.
Hydrology
Yields are sufficient for domestic use near outcrop areas of Paleozoic
bedrock and in areas of perched water. Where the formation is thick,
drilled wells yield as much as 830 gallons per minute. In areas where formation
is mostly silt and clay, there may not be sufficient saturated sand
to furnish even a domestic supply. Hardness of water ranges from 13
to 182 ppm, and dissolved solids from 62 to 275 ppm. Iron may be present
in objectionable amounts. Best potential for large yields to wells is
in central and southern Marshall County The yields increase southward
from central Marshall County to Tennessee. Wells in northern Marshall
County have lower yields but are adequate for domestic use.
Tuscaloosa Formation (Kt)
Topography
The Tuscaloosa may occur in remnants of channel eroded into surface
of the Paleozoic rocks. It underlies dissected ridges adjacent to Kentucky
Lake.
Hydrology
The Tuscaloosa is not significant as an aquifer. Most drilled wells
in the gravel of the Tuscaloosa are adequate for a bailer (more than
100 gallons per day). Yields are low, owing to clayey matrix and poor sorting.
Tripolitic clay is present locally which tend to clog well screens and
wells penetrating it are inadequate (less than 100 gallons per day). Hardness
of water from two wells sampled was 26 and 57 ppm, and dissolved solids,
50 and 76 ppm. Yields adjacent to Kentucky Lake may exceed 5 gallons per minute.
Chert Rubble
Topography
Chert rubble occurs mostly in the subsurface around the periphery of
the embayment; its extent beneath the embayment is not known. The surface
of the Paleozoic rocks locally has been reduced to a chert rubble by
pre-Late Cretaceous weathering of the chert-bearing limestone.
Hydrology
Chert rubble probably will yield more than enough water for domestic
use; locally, it may yield sufficient water for small public supplies.
Yields are as large as 100 gallons per minute. Yields vary with the saturated thickness
of the rubble and characteristics of the rubble’s matrix. Hydrologic
properties resemble those of gravel. The water level in the rubble slopes
downward from highs on the limestone surface towards collapse structures
(areas of thick chert rubble formed by solutional collapse along fracture
zones and former drainage channels). The water is soft and has a low
content of dissolved solids but may contain an objectionable amount
of iron, which probably is derived from the iron-rich clay that commonly
fills voids in the rubble.
Warsaw Limestone (Mw)
Topography
The Warsaw underlies dissected uplands and ridges adjacent to the Cumberland
and Tennessee Rivers.
Hydrology
In the Jackson Purchase Region west of Kentucky Lake, no wells in the
bedrock are known that do not yield enough water for domestic use.
Fort Payne Formation (Mbf)
Topography
The Fort Payne underlies dissected ridges between Tennessee and Cumberland
Rivers. It is present in fault blocks under the embayment sediments.
Hydrology
In the Jackson Purchase Region west of Kentucky Lake, no wells in the
bedrock are known that do not yield enough water for domestic use.
The U.S. Geological Survey's Hydrologic
Atlas Series, published cooperatively with the Kentucky Geological
Survey, provides hydrologic information for the entire state.
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