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Alluvium (Qa)/Glacial Deposits (Qg)
Topography
These unconsolidated materials form floodplains and terraces of the
Ohio River and tributaries. The highest terraces are about 100 feet
above normal pool level of the Ohio River. The material is too thin
in tributary valleys to have distinctive topography.
Hydrology
Unconsolidated materials yield moderate to large quantities of water
to drilled wells in the Ohio River Valley, depending on thickness and
texture of the valley fill and type of well; they yield 200 to 500 gallons
per minute to ordinary tubular wells and as much as 1,000 gallons per
minute to gravel-packed wells. These materials yield little water from
fine-grained material. A small to moderate amount of water is yielded
to drilled wells in the Licking River Valley; most wells yield more
than 500 gallons per day. Water is hard, and near the valley walls of
the Ohio and Licking Rivers may have a high iron content. Wells that
penetrate the alluvium and enter bedrock obtain little additional water,
and this water may contain objectionable amounts of salt or hydrogen
sulfide.
Grant Lake Limestone/Fairview Formation (Oaf)
Topography
The Grant Lake and Fairview form gently to moderately rolling uplands
away from major streams such as the Ohio and Licking Rivers, and moderately
dissected uplands where shale content increases. They form steep dissected
slopes along large streams, with ledges of thick limestone beds on steep
hillsides and bluffs along streams. Streams in uplands produce broad,
flat valleys where thick limestone beds are present; small sinkholes
with minor underground drainage may be present. Low hills on uplands
also may be capped by thick limestone beds. The lower part forms broad,
flat ridges between steep-sided valleys cut into the underlying shale
of the Kope Formation.
Hydrology
These rocks yield 100 to 500 gallons per day to drilled wells in valley
bottoms, and along streams on uplands; thick limestone beds in broad
valley bottoms yield more than 500 gallons per day. Almost no water
is yielded to wells on hillsides or hilltops; some water may be yielded
to dug wells on ridgetops, and some water to small springs. Small perennial
springs occur in limestone in the lower Grant Lake Limestone. Water
is hard, and in valley bottoms may contain salt or hydrogen sulfide.
The relatively impermeable shale prevents circulation of large quantities
of groundwater in joints and bedding-plane openings of relatively soluble
underlying limestone. As a result, the limestone beds have few solutionally
enlarged openings, so little water is available to wells and springs.
Near the base of the Grant Lake, however, is 25 feet or more of limestone
with small amounts of shale (Bellevue Limestone Member), and where this
limestone occurs at and below stream level in valley bottoms or along
streams on the uplands, fractures and bedding-plane openings have been
enlarged by solution. Many small springs flow from outcrops, and some
drilled wells along streams yield more than 500 gallons per day.
Kope Formation (Okc)
Topography
The Kope forms rugged, much-dissected topography of long, narrow, steep-sided
ridges and narrow, winding, V-shaped valleys with a dendritic drainage
pattern. Steep slopes are littered with thin limestone slabs that remain
as shale erodes and washes away. The contrast with less-rugged upland
surfaces of adjacent areas is marked, except near major streams, where
change is masked by dissection.
Hydrology
The Kope yields 100 to 500 gallons per day to drilled wells in valley
bottoms along large streams, but almost no water to drilled wells on
hillsides or ridgetops. It also yields water to small springs and seeps.
Water is hard in valley bottoms, and may contain salt or hydrogen sulfide.
Shale units have small, poorly connected openings that allow passge
of only small quantities of water, restricting yields to wells and springs
and preventing recharge to underlying rocks. The few thick limestone
beds may yield water to small springs. On ridgetops, shale impedes downward
percolation of water and supports water in the lower part of the soil
and in the weathered-rock zone just beneath the soil. High up on the
sides of many ridges is a zone of seeps and small springs; where the
Grant Lake caps the ridges, the zone is generally near or at the contact
with the Kope Formation. Drilled wells on these ridges obtain a little
water at the contact between soil and bedrock, but rarely at greater
depths; if water is found at depth, it is mainly in small quantities
and of poor quality. Dug wells, with large wall areas, are better suited
for obtaining water from these bodies of water; however, many go dry
in late summer and fall.
Clays Ferry Formation and Its Point Pleasant Tongue (Okc)
Topography
The Clays Ferry lies in broad, flat valley bottoms along large streams
between steep, narrow ridges. The limestone has undergone solution,
and in some areas is characterized by small sinkholes and subsurface
drainage. Smaller streams develop long, narrow, winding, V-shaped valleys
similar to those of the Kope Formation.
Hydrology
This formation yields more than 500 gallons per day to wells drilled
in valley bottoms, and small amounts of water to wells on hillsides
and hilltops. It also yields water to small springs. Water is hard or
very hard, and may contain salt or hydrogen sulfide, particularly in
wells in valley bottoms; both, especially hydrogen sulfide, may be found
in wells on hillsides. Beneath broad interstream areas, much solutional
enlargement of fractures and bedding-plane openings has taken place
in the soluble zones beneath tributary streams, allowing many drilled
wells to produce 100 to 500 gallons per day. Some wide, flat areas have
small sinkholes and some underground drainage.
Lexington Limestone (Tanglewood Limestone, Grier, Logana Members)
(Ol)
Topography
Limestones lie in flat valley bottoms along the Licking River.
Hydrology
Limestones yield more than 500 gallons per day to wells in valley bottoms,
and as much as 150 gallons per minute in places. Water is hard, and
may contain salt or hydrogen sulfide in some places.
The U.S. Geological Survey's Hydrologic Atlas Series, published cooperatively
with the Kentucky Geological Survey, provides hydrologic information
for the entire state. Atlases for the county are HA-16,
HA-94.
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