Alluvium (Qa)
Topography
Alluvium forms terraces and narrow floodplains of varying width along
streams.
Hydrology
The alluvium yields almost no water to drilled wells, but small quantities
to dug wells.
High-Level Fluvial Deposits (QTf)
Topography
These deposits occur on uplands and hilltops having no distinct surface
expression.
Hydrology
These deposits yield small amounts of water to wells and springs.
Breathitt Group (Pbl) (Pikeville Formation)
Topography
The topography of the Breathitt is rugged. Sandstone forms narrow valleys
and cliffs or steep slopes on hillsides, and shale forms wide valleys
and moderate or gentle slopes on hills. Tops of hills and ridges commonly
are capped by sandstone.
Hydrology
The Breathitt yields more than 500 gallons per day to almost half the
wells in valley bottoms and very little to wells on hillsides and hilltops.
Most common aquifers are sandstone and shale, but coal supplies water
to a few wells. Near-vertical joints and openings along bedding plains
yield most of the water to wells. Waters are highly variable in chemical
character. Wells may contain salty water at depths less than 100 feet
below the principal valley bottoms.
Grundy Formation (contains Lee-type sandstone of the former Lee
Formation) (Plc)
Topography
The Grundy forms ridgetops in southern Rowan County, and somewhat dissected
uplands in southeastern Rowan County. The upper part of the Grundy erodes
easily and forms broad, flat ridges. The lower part is more conglomeratic
and resistant, caps knobs and narrow ridges, and in many places forms
steep walls high on the sides of ridges. The Grundy underlies valleys
only in southeastern Rowan County. Some cliff-forming sandstone paleochannels
have been cut through the Paragon Formation into Upper Mississippian
limestone units.
Hydrology
The Grundy yields more than 500 gallons per day to most wells drilled
in broad valley bottoms, and smaller quantities of water to wells on
hillsides and hilltops. It yields 100 to 500 gallons per day on some
wide ridges, where water may be semiperched in sandstone on top of fire
clay that 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, and sometimes
contain noticeable amounts of iron, but generally have a low dissolved-solids
content.
Slade Formation (Mn)
Topography
Limestone beds in the Slade form steep hillsides and prominent bluffs
in sides of ridges and knobs that are capped by Pennsylvanian rocks.
Massive limestone forms cliffs and solution features such as sinkholes,
caves, and hanging valleys.
Hydrology
The Slade yields more than 500 gallons per day to over half of the wells
drilled in valley bottoms, and to many wells drilled on hills. It yields
little water where overlain by Pennsylvanian rocks. It may yield more
than 50 gallons per minute to a few wells penetrating large solution
cavities in limestone, the most common aquifer. 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
Shale in the Borden forms dissected slopes; massive siltstone forms
cliffs.
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. It yields 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 upland surfaces, as
well as 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, but little water to drilled wells on
hillsides and hilltops. It does yield water to small springs and seeps.
Water may be soft or highly mineralized. Salt, hydrogen sulfide, and
iron are the usual objectionable constituents. Acid 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 Boyle yields little water to wells, but does yield water to many
small perennial springs. Water is hard.
Crab Orchard Formation and Brassfield Dolomite (Scb)
Topography
Shale forms steep, dissected hillsides and broad, flat valley bottoms,
eroding 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. They yield water 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.
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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