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Alluvium (Qa)
Topography
The alluvium forms narrow flood plains and underlies terraces. At least
one well-developed terrace is present along the principal streams of
the region.
Hydrology
The alluvium yields more than 100 gal/min to most dug wells. Where sandy
material is present and saturated thickness great enough would yield
more than 500 gal/day to screened drilled wells. Water is soft or moderately
hard; may contain large amounts of iron at depth.
Breathitt Group (Pbl) (Pikeville Fm.)
Topography
The Breathitt Group underlies the valleys and forms the hills. Tops
of hills and ridges commonly are capped by sandstone. Shales form wide
valleys and moderate or gentle slopes on hills.
Hydrology
The Breathitt yields more than 500 gal/day to almost half of the wells
drilled in valley bottoms, and more than 100 gal/day to about half the
wells drilled on hillsides and on ridges. Sandstones yield water to
most wells. Shales also yield water to many wells, and coal yields water
to a few. Near-vertical joints and openings along bedding plains yield
most of the water to wells. Waters are highly variable in chemical character.
Corbin (Plc) and Rockcastle (Plr) Sandstone Members, Grundy, Alvy
Creek and Bee Rock
Formations (contains Lee type sandstone of the former Lee Formation)
Topography
The thick, resistant sandstones of these formations lie at the tops
of steep-sided ridges and knobs, steep bluffs and cliffs. Shaly facies
crop out in Jackson County, forming a highly- dissected area of winding
ridges and steep-sided hills. Some cliff-forming sandstone paleochannels
have been cut through shales of the Paragon Formation into limestone
units of Late Mississippian.
Hydrology
In most of Jackson County these rocks yield more than 100 gal/day to
about three-quarters of the wells drilled on hilltops, and larger quantities
of water to wells on hillsides and valley bottoms. Sandstone is the
principal aquifer, but shale yields water to some wells and coal to
a few. Joints and openings along bedding planes, best developed in sandstone,
supply most of the water to wells. Perched and semi-perched water tables
are common. Waters are generally soft or moderately hard and contain
noticeable amounts of iron.
Paragon Formation (Mpn)
Topography
The Paragon forms moderate to steep slopes in mountain margin area where
capped by massive sandstone of Breathitt Group.
Hydrology
The Paragon yields almost no water. Impermeable shale may hold water
in overlying sandstone and conglomerate.
Borden Formation (MDbb)
Topography
The shale forms dissected slopes, the massive siltstone forms cliffs,
and the limestone forms ledges on shale slopes and broad, flat valleys.
Hydrology
The Borden yields 100 to 500 gal/day to wells in valley bottoms, and
may yield more than 500 gal/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 at less than 100 feet. 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, and
steep, dissected hillsides and bluffs along streams.
Hydrology
The New Albany yields 100 to 500 gal/day to drilled wells in valley
bottoms and on uplands, usually at depths of less than 50 feet. Water
from depths greater than 50 feet is highly mineralized. The shale yields
water to small springs. Water may be soft or highly mineralized. Salt,
hydrogen sulfide, and iron are the usual objectionable constituents.
Boyle Dolomite (MDnb)
Topography
The Boyle forms resistant ledges on valley sides between shale slopes
above and below.
Hydrology
The dolomite yields almost no water to drilled wells, but does yield
water to many small perennial springs. Water is hard but otherwise of
good quality.
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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