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Salem and Warsaw Formations (Msh)
Topography
These limestone beds form steep hillsides and prominent bluffs on
sides orf ridges and knobs. They are capped by rocks of Pennsylvanian
age.
Hydrology
These formations yield 100 to 500 gallons per day to drilled wells
in the few places where they occur below stream level; they yield almost
no water to wells on narrow ridgetops or hillsides. They yield some
water to small springs on hillsides, particularly at the heads of streams.
Springs have large winter and small summer flows. Water is hard to very
hard.
Borden Formation (MDbb, Mbf)
Topography
The Borden forms the main part of the Mississippian escarpment,
ridges, and knobs. Shale forms dissected slopes, massive siltstone forms
cliffs, and limestone forms ledges on shale slopes.
Hydrology
The Borden yields 100 to 500 gallons per day to wells in valley
bottoms; it may yield more than 500 gallons per day to drilled wells
in broad valley bottoms, from fractured sandy rocks near streams, but
it yields almost no water to wells on hills. Water from wells drilled
below stream level may contain salt, sulfate, or iron less than 100
feet below the level of the principal valley bottoms. Water from dug
wells and small springs is soft, and has a low total dissolved solids
content. Water from shale is soft; from the siltstone, hard; and from
the limestone, very hard. Because much of this formation is soft and
silty, it has been well suited to the construction of dug wells in the
past.
New Albany Shale (MDnb)
Topography
The New Albany lies in broad, flat valleys; flat upland surfaces;
steep, dissected hillsides; and bluffs along streams.
Hydrology
The New Albany yields 100 to 500 gallons per day to drilled wells
in valley bottoms and on uplands, usually at depths of less than 50
feet; water from greater depths is highly mineralized. The New Albany
yields water to small springs as well. Water may be soft or highly mineralized.
Salt, hydrogen sulfide, and iron are the usual objectionable constituents.
Drakes Formation (Saluda Dolomite, Bardstown, Rowland Members) (Odc)
Topography
The Drakes is somewhat dissected in upland areas; it forms moderately
steep slopes where shale predominates, and moderately undulating to
gently rolling surfaces where limestone predominates. Slopes are steep
to cliff-like and dissected along large streams; many are littered with
limestone slabs left after shale erodes and washes away. Small sinkholes
with some underground drainage are present where thick limestone beds
occur along broad upland stream valleys.
Hydrology
The Drakes yields 100 to 500 gallons per day to drilled wells in
broad valleys and along streams in uplands; it yields almost no water
to drilled wells on hillsides or ridgetops, and some water to small
springs. Water is hard, and in valley bottoms may contain salt or hydrogen
sulfide. Shale limits the amount of water that has access to thick limestone
beds, and therefore restricts the number of openings in these beds that
may be enlarged by solution. As a result, the limestone beds yield little
water.
Ashlock Formation, Grant Lake Limestone, Calloway Creek Limestone
(Oaf)
Topography
These formations form gently to moderately rolling uplands away
from major streams; they are more highly dissected where shale content
increases. The rocks form dissected and steep ledges along large streams.
Thick limestone beds stand out as ledges along steep hilssides and bluffs
along streams; where present on uplands, these formations underlie broad,
flat valleys that may have small sinkholes and some underground drainage.
The lower part of the Calloway Creek caps broad, flat ridges between
steep-sided valleys cut into underlying shale of the Clays Ferry Formation.
Hydrology
These rocks yield 100 to 500 gallons per day to drilled wells in
broad valleys and along streams in uplands. Where thick limestone beds
with little shale occur below stream level in valley bottoms or on uplands,
they may have undergone solutional enlargement of fractures and bedding-plane
openings. Wells drilled into these limestone beds may produce more than
500 gallons per day. These thick beds also yield water to some large
springs. The rocks yield almost no water to drilled wells on hillsides
or ridgetops, but do yield water to small springs and seeps. A limestone
bed 15 feet thick in the lower part of the Grant Lake Limestone yields
as much as 30 gallons per minute to springs. A sandy zone near the base
yields little water. Water is hard, and in valley bottoms may contain
salt or hydrogen sulfide.
Garrard Siltstone (Okc)
Topography
The Garrard forms prominent ledges along hillsides.
Hydrology
The well-cemented siltstone and fine-grained sandstone and siltstone
do not provide many openings for water, and yield almost no water to
wells. Water is hard.
Clays Ferry Formation (Okc)
Topography
The Clays Ferry forms rugged, dissected topography of long, narrow,
winding, steep-sided ridges with narrow, winding, V-shaped valleys of
dendritic drainage pattern. Shales on steep slopes erode easily, and
are covered with thin limestone slabs in many places. The contrast with
the rolling upland outcrops areas of the overlying Drakes, Grant Lake,
and Callow Creek formations is striking, except along large streams,
where change is masked by dissection. In the lower part of the formation,
topography becomes more gently to moderately rolling uplands, with small
sinkholes and some underground drainage where limestone predominates.
Hydrology
The Clays Ferry yeilds 100 to 500 gallons per day to drilled wells
in large valley bottoms along streams, but almost no water to drilled
wells on hillsides or ridgetops; it may yield some water to dug wells
on ridgetops. It also yields water to small springs and seeps. Water
is hard, and in valley bottoms may contain salt or hydrogen sulfide.
Shale has small, poorly connected openings, and groundwater ciruclation
is slow; as a result, little water is available to wells and springs.
On ridgetops, the shalae impedes downward percolation of water and holds
up water in the soil and weathered-rock zone. Dug wells, having large
wall areas, are best suited for obtaining this water. On broad ridges
capped by the Grant Lake or Calloway Creek formations, the underlying
Clays Ferry holds up a semiperched water body in the Grant Lake and
Calloway Creek, and dug wells produce some water; however, wells often
go dry in late summer and fall.
Upper Part of the Lexington Limestone (Tanglewood Limestone, Millersburg,
Strodes Creek, Devils Hollow, Sulfur Well, Brannon, and Perryville Members)
(Ol)
Topography
Limestones lie in braod, flat valleys in uplands; where dominantly
limeestone, there is well-developed subsurface drainage and many sinkholes.
Gently sloping hillsides are adjacent to small streams in uplands. The
resistant shale and soft bentonite-rich beds form a subdued, bench-like
topography along hillsides and streams.
Hydrology
These limestones yield more than 500 gallons per day to wells in
valley bottoms and along streams in uplands, 100 to 500 gallons per
day to many perennial springs, and more than 100 gallons per minute
to a few large springs. The amount of water available in rocks of the
Lexington Limestone is dependent on the amount of shale. Generally,
throughout the whole Lexington Limestone section, the more shale found
within the zone of interest, the less water will be found. The formation
yields water to springs from the resistant Brannon Member. Water is
hard and may contain salt or hydrogen sulfide in some places. Water
from wells near fault zones may contain objectionable amounts of salt.
Lower Part of the Lexington Limestone (Grier, Logana, and Curdsville
Members) (Ol)
Topography
The lower Lexington forms rolling to dissected uplands. Sinkholes
are very common; the large ones occur in the Grier Limestone. Natural
outcrops are rare in the rolling upland, but the limestone beneath hillslopes
is evident from the bench-like or terrace-like appearance of the slopes.
Limestone crops out in discontinuous bands in the valley sides in the
dissected part near the Kentucky River.
Hydrology
The limestones yield 100 to 500 gallons per day to wells in most
valley bottoms and along streams in uplands; wells yield up to 150 gallons
per minute from thick limestone beds in the Curdsville along large streams.
The limestones yield water to many small springs. Water is hard and
may contain salt in valley bottoms.
High Bridge Group (Tyrone Limestone, Oregon Formation, Camp Nelson
Limestone) (Ohb)
Topography
The High Bridge forms steep slopes and high cliffs along the Kentucky
and Dix Rivers and lower parts of tributaries. The Camp Nelson forms
flat terraces with occasional sinkholes in the bottom of the Kentucky
River gorge and steep cliffs along the lower sides. It also extends
up the large tributaries, forming flat bottoms and steep walls. The
Oregon crops out in a band in the walls of the gorge and up a few large
tributaries. The Tyrone crops out in the upper walls of the Kentucky
River gorge, and extends up the large tributaries nearly to the upland,
forming broad, flat valleys with sinkholes and underground drainage.
Hydrology
The High Bridge yields 100 to more than 500 gallons per day to drilled
wells in valleys of the Dix and Kentucky Rivers and large tributaries.
It yields as much as 30 gallons per minute to drilled wells along the
shores of Harrington Lake. Yields of as much as 225 gallons per minute
have been reported in wells drilled into the Camp Nelson Limestone adjacent
to the Kentucky River, from solution channels and fractures connected
with the river. The High Bridge yields water to springs on hillsides
and in steep walls along large streams. Water is hard and may contain
hydrogen sulfide, but is generally of good quality. Wells drilled into
the High Bridge through overlying rocks produce almost no water, because
bentonite beds in the Tyrone prevent recharge to underlying rocks, except
where the bentonite has been breached or removed by erosion.
Knox Group (Okx)
Topography
There is no surface exposure of the Knox in Kentucky, but it underlies
the entire state at varying depths.
Hydrology
In the Inner Bluegrass Region, fresh water has been found in the
upper 100 to 250 feet of this large untested dolomite-rich aquifer.
Wells often exceed 750 feet in total depth, with high concentrations
of total dissolved solids in many areas. Average reported yields range
from 10 to 20 gallons per minute, but as high as 75 gallons per minute.
You can find out more about the Knox
aquifer.
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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