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Alluvium (Qa)
Topography
Alluvium forms terraces and narrow floodplains of varying width along
streams.
Hydrology
The unconsolidated material yields almost no water to drilled wells;
small quantities are yielded to dug wells.
Grundy Formation (contains Lee-type sandstone of the former Lee
Formation) (Plc)
Topography
The upper part of the formation erodes easily and forms broad, flat
ridges. The lower part is more conglomeratic and resistant, and caps
knobs and narrow ridges; in many places the Grundy forms steep walls
high on the sides of ridges. Some cliff-forming sandstone paleochannels
have been cut through the Paragon Formation into limestone units of
Late Mississippian age.
Hydrology
Most wells yield more than 500 gallons per day when drilled in broad
valley bottoms and smaller quantities of water when drilled in hillsides
and hilltops. Yields are 100 to 500 gallons per day on some wide ridges
where water may be semiperched in sandstone on top of fireclay, which
impedes downward percolation of water. Sandstone is the principal aquifer,
but shale yields water to some wells and coal to a few. Vertical joints
and openings along bedding planes, best developed in sandstones, supply
most of the water to wells. Intergranular openings yield water to joints,
and probably directly to some wells. Perched and semiperched water tables
are common. Waters are soft to moderately hard, sometimes contain noticeable
amounts of iron, but generally have a low dissolved solids content.
Slade Formation (Mn)
Topography
The limestone beds form steep hillsides and prominent bluffs in sides
of ridges and knobs that are capped by rocks of Pennsylvanian age. Massive
limestone forms cliffs and solution features such as sinkholes, caves,
and hanging valleys.
Hydrology
The limestone yields more than 500 gallons per day to over half of the
wells drilled in valley bottoms, and to many wells drilled on hills.
The limestone yields little water where overlain by Pennsylvanian rocks,
but may yield more than 50 gallons per minute to a few wells penetrating
large solution cavities. Sandstone and shale yield water from fractures
to a few wells. Springs are common, particularly at the head of streams;
some from solution cavities near stream level flow as much as 100 gallons
per minute. Springs have large winter and small summer flows. Water
is hard.
Borden Formation (MDbb)
Topography
The 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 almost no
water to wells on hills. Water from wells drilled below stream level
may contain salt and sulfate 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 dissolved solids content. 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 forms broad, flat valleys and flat uplands; steep, dissected
hillsides and bluffs are formed along streams.
Hydrology
The shale yields 100 to 500 gallons per day to drilled wells in valley
bottoms and on uplands; little water is yielded to drilled wells on
hillsides and hilltops. Water is yielded to small springs and seeps.
Water may be soft or highly mineralized. Salt, hydrogen sulfide, and
iron are the usual objectionable constitutents. Acidic water with high
sulfate content is found in places. Shale has small, poorly connected
openings, and groundwater circulation is slow; however, the shale is
commonly fractured to a depth of at least 40 feet, and fractures form
the main reservoir for water in this formation.
Boyle Dolomite (MDnb)
Topography
The Boyle forms prominent ledges along hillsides and lower edges of
valleys.
Hydrology
The dolomite yields little water to wells, and some water to many small
perennial springs. Water is hard.
Crab Orchard Formation and Brassfield Dolomite (Scb)
Topography
The shale forms steep, dissected hillsides and broad, flat valley bottoms;
it erodes readily below more-resistant overlying limestone, forming
notches and recesses. Dolomite beds form discontinuous ledges along
hillsides.
Hydrology
These formations yield 100 to 500 gallons per day to wells in broad
valley bottoms, but almost no water to wells on hills; some water is
yielded to small springs and seeps. Water is hard and locally contains
magnesium and calcium sulfate dissolved from epsom salt and selenite
(gypsum) in the shale. Dolomite beds yield hard water to small springs.
Drakes Formation (Odb)/Bull Fork Formation (Ob)
Topography
These formations provide gently to moderately rolling uplands except
along large streams, where there is considerable dissection, with slopes
moderately steep where underlain by shale, and moderately undulating
to gently rolling where underlain by limestone. Steep and cliff-prone
slopes lie along large streams; they are littered with limestone slabs
left as shale beds weathered and washed away.
Hydrology
These formations yield 100 to 500 gallons per day to drilled wells in
broad valleys and along streams in upland areas; almost no water is
yielded to drilled wells on hillsides or ridgetops. Some water is yielded
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 can be enlarged by solution. As a result, the limestone
beds yield little water. In locations where groundwater has ready access
to thick limestone beds along streams, wells and springs have larger
yields.
Grant Lake Limestone/Fairview Formation/Calloway Creek Limestone
(Oaf)
Topography
These formations provide gently to moderately rolling uplands, except
along major streams, where there is considerable dissection that leaves
steep slopes. Thick limestone beds stand out as ledges on steep hillsides
and bluffs along streams; where present on uplands, they underlie broad,
flat valleys that may have small sinkholes and some underground drainage.
Hydrology
Yields are 100 to 500 gallons per day to drilled wells in broad valleys
and along streams in upland areas; almost no water is yielded to drilled
wells on hillsides or ridgetops. Yields are 100 to 500 gallons per day
to wells drilled into thick limestone beds along streams in uplands,
and thick limestone beds capping hills on uplands. Thick limestone beds
yield water to small springs along valley bottoms and hillsides. Water
is hard and in valley bottoms may contain salt or hydrogen sulfide.
Garrard Siltstone (Okc)
Topography
The Garrard lies in prominent ledges in steep slopes and bluffs along
large streams.
Hydrology
Yields are 100 to 500 gallons per day to drilled wells in valley bottoms,
but almost no water is produced by wells on hillsides or ridgetops,
and almost no water from springs. The well-cemented siltstone and fine-grained
sandstone do not provide many openings for water. Water is hard.
Clays Ferry Formation (Okc)
Topography
The Clays Ferry lies in broad, flat valley bottoms along the Licking
River.
Hydrology
The formation yields 100 to 500 gallons per day to wells drilled in
broad valley bottoms, and some water to small springs. Water is hard
and 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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