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Alluvium (Qa) and Glacial Sediments (Qg)
Topography
These unconsolidated materials form floodplains and terraces, as much
as 6 miles wide, in the Ohio River valley, and broad flat areas in the
valleys of the Salt River and large tributaries. They also form extensive
floodplains with small terraces along Rolling Fork. Some Ohio River
terraces are as much as 80 feet above normal pool stage. Flats are dissected
by short, steep-sided gullies near tributaries.
Hydrology
The sediments yield 100 to more than 500 gallons per day (gallons per day) from
thick deposits along Rolling Fork. They yield 200 to 500 gallons per minute (gallons
per minute) to most wells that penetrate the full thickness of alluvium
in the Ohio Valley, and yield more than 1,000 gallons per minute to largediameter
wells. Yields are 100 to 500 gallons per day to wells in tributary-stream valleys,
and may be more than 500 gallons per day where gravel is present. Water is hard,
and the iron content may be high near the Ohio River valley walls.
Middle Mississippian Limestone (St. Louis, Salem, Harrodsburg Limestones)
(Msh), (Mgl)
Topography
These limestons top of some of the high ridges and knobs in northern
Bullitt County.
Hydrology
The limestones yield 100 to 500 gallons per day to drilled wells on broad uplands,
but almost no water on narrow ridges; yields water to small springs
in edges of escarpment. Water is hard but otherwise of good quality.
Borden Formation (Muldraugh (Mbf), Halls Gap, Nancy, New Providence
Members (MDbb))
Topography
This formation is the main part of the Muldraugh escarpment, ridges,
and knobs. Resistant rocks of the Muldraugh member cap the escarpment
and larger knobs. Minor limestone beds form ledges and small cliffs.
Shale forms steep slopes, and the more resistant siltstone beds form
ledges on slopes and in ravines.
Hydrology
These rocks yields 100 to 500 gallons per day to wells in valley bottoms, and
may yield more than 500 gallons per day where thick siltstone beds occur at
and below stream level. They yield almost no water to wells on hills,
but do yield water to small springs in the limestone and siltstone beds.
Water from the shale is soft, from the siltstone, hard, and from the
limestone, very hard. At shallow depths below stream level, water may
contain salt, sulfate, or iron. The silty shale and siltstone are favorable
for dug wells, common in this area. Most dug wells yield less than 500
gallons per day and many yield little or go dry in late summer and early fall.
New Albany Shale (MDnb)
Topography
The New Albany forms broad, flat areas in southwest-central Jefferson
and central Bullitt counties, and gentle lower slopes of much of the
Mississippian escarpment and the knobs.
Hydrology
The shale yields 100 to 500 gallons per day to shallow drilled wells in broad,
flat areas, but almost no water to drilled wells on hillsides; yields
water to small springs and wells dug almost any place in the black shale.
Water is in fractures that extend less than 50 feet below land surface.
Water is hard and from depths greater than 50 feet may contain hydrogen
sulfide and iron.
Louisville Limestone (Slw)
Topography
The Louisville forms moderately rolling uplands with some sinkholes
and underground drainage in north-central Bullitt County. Forms cliffs
and ledges in valley sides.
Hydrology
The limestone yields more than 500 gallons per day to wells drilled in valley
bottoms or along streams on broad uplands; yields as much as 50 gallons per minute
in places; yields water to springs at contact with underlying Waldron
shale. Water is hard and may contain salt or hydrogen sulfide below
stream level.
Waldron Shale (Slw)
Topography
The Waldron forms slopes between limestone ledges on hillsides; erosion
of shale undermines overlying Louisville limestone.
Hydrology
The shale yields almost no water to wells or springs. It holds up water
in the overlying Louisville limestone and prevents recharge to the underlying
Laurel dolomite. Water is hard.
Laurel Dolomite (Slb)
Topography
The Laurel forms ledges and cliffs along streams.
Hydrology
The dolomite yields 100 to 500 gallons per day to wells on broad ridges and
along streams; yields water to small springs at contact with underlying
Osgood formation. Water is hard.
Osgood Formation (Slb)
Topography
The Osgood forms steep, dissected hillsides. It erodes easily, undermining
the Laurel and forms slopes between ledges above and below.
Hydrology
The Osgood yields almost no water, impedes recharge to the Drakes Formation,
and holds up water in the Laurel. The limestone does yield water to
small springs. The water is hard.
Brassfield Formation (Slb)
Topography
The Brassfield forms ledges on slopes and tops of small cliffs of underlying
Saluda limestone.
Hydrology
The Brassfield yields almost no water to wells; yields water to seeps
and small springs. Water is hard.
Drakes Formation (Saluda Dolomite, Bardstown, Rowland Members) (Od)
& Bull Fork
Formation (Ob)
Topography
These formations form somewhat dissected upland areas; moderately steep
slopes where shale predominates, moderately undulating to gently rolling
surface where limestone predominates. Slopes are steep to cliffy 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
These rock bodies yield 100 to 500 gallons per day to wells in large stream
valleys, and more where thick limestone is present. They yield almost
no water to wells on hillsides and ridges except in broad ridges in
upper part of formation. They do yield water to small springs. Shale
prevents circulation of water in thicker limestone beds except where
limestone is exposed on flat ridges or valley bottoms. Water is hard
and may contain salt in valley bottoms but generally of good quality.
Grant Lake Limestone, Calloway Creek Limestone (Oaf)
Topography
These limestones form gently to moderately rolling uplands away from
major streams, which are more highly dissected where shale content increases.
They are dissected and steep along large streams. Thick limestone beds
stand out as ledges along steep hillsides and bluffs along streams,
and where present on uplands underlies broad, flat valleys that may
have small sinkholes and some underground drainage.
Hydrology
These limestones yield 100 to 500 gallons per day to drilled wells in broad
valleys and along streams in uplands; yield more than 500 gallons per day from
thick limestone beds in the broad valley bottoms; yield almost no water
to drilled wells on hillsides or ridgetops; yield water to small springs
and seeps. Limestone bed 15 feet thick in lower part of the Grant Lake
Limestone yields as much as 30 gallons per minute to springs. The sandy zone near
the base yields little water. Water is hard and in valley bottoms may
contain salt or hydrogen sulfide.
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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