Alluvium (Qa), glacial sediments (Qg)
Topography
Alluvium and glacial sediments form floodplains and terraces of the
Ohio and Licking River Valleys. Highest terraces are about 100 feet
above normal pool level of the Ohio River. These unconsolidated materials
also form floodplains and terraces along tributaries. The alluvium is
too thin in tributary valleys to have a distinctive topography.
Hydrology
The unconsolidated materials yield moderate to large quantities of water
to drilled wells in the Ohio River Valley, depending on the thickness
and texture of the valley fill and type of well. Yields of 200 to 500
gallons per minute may be obtained from ordinary tubular wells, and
as much as 1,000 gallons per minute may be obtained from gravel-packed
wells. Little water is yielded by fine-grained material. Water is hard,
and near the valley walls of the Ohio 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.
Bull Fork Formation (Ob)
Topography
The Bull Fork forms moderately rolling uplands where limestone predominates;
topography is more dissected where shale predominates.
Hydrology
The Bull Fork yields 100 to 500 gallons per day to wells in valleys
or on broad ridges, but almost no water to drilled wells on narrow ridges
or hilltops. Some water is yielded to dug wells and to small springs.
Water is hard and of good quality.
Grant Lake Limestone/Fairview Formation (Oaf)
Topography
These rock bodies form gently to moderately rolling uplands away from
major streams such as the Ohio River, moderately dissected uplands where
shale content increases, and steep dissected slopes along large streams.
There are also 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; there may be small sinkholes
with minor underground drainage. 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. More than 500 gallons per day
is yielded from thick limestone beds in broad valley bottoms; almost
no water is yielded to wells on hillsides or hilltops. Some water may
be yielded to dug wells on ridgetops and 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, and little water is available to wells and springs.
However, near the base of the Grant Lake there is 25 feet or more of
limestone with small amounts of shale (Bellevue limestone member). 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 dendritic drainage
pattern. Steep slopes are littered with thin limestone slabs that remain
as shale erodes and washes away. Contrast with the 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. The Kope 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 passage
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; however, many go dry in late
summer and fall.
U.S. Geological Survey's Hydrologic Atlas Series, published cooperatively
with the Kentucky Geological Survey, provides hydrologic information
for the entire state. Atlases for Boone County are HA-15,
HA-98 .
Previous--Next--Back
to "Groundwater Resources in Kentucky"
|