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Alluvium (Qa)
Topography
The alluvium forms narrow floodplains 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 gallons per day to most dug wells. Where sandy
material is present
and the saturated thickness is great enough, the alluvium may yield
more than 500 gallons per day to
screened drilled wells. Wells in the Red River valley often yield more
than 500 gallons per day. Water is
soft or moderately hard; may contain large amounts of Iron at depth.
High-Level Fluvial Deposits (QTf)
Topography
These deposits lie in uplands and on hilltops, with no distinct surface
expression.
Hydrology
Yields 100 to 500 gallons per day to wells in thick deposits; yields water to
small springs. Water is soft.
Breathitt Group (Pbm, Pbl) (Four Corners Formation, Hyden Formation,
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 of the wells
drilled in valley bottoms
and less to wells on hillsides and hilltop. Sandstone yields water to
most wells. Shale also
yields 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. 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 upland formed by the Grundy is highly dissected and characterized
by steep-sided ridges and
cliffs 100 to 200 feet high. Waterfalls and rock bridges, such as Natural
Bridge and Sky Bridge,
are common. Some cliff-forming sandstone paleochannels have been cut
through the Paragon
formation into limestone units of Late Mississippian.
Hydrology
The Grundy yields 100 to 500 gallons per day to wells in thick deposits, and
yields water to small
springs. 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. Inter-granular openings yield water to joints,
and probably directly to
some wells. Perched and semi-perched water tables are common. Waters
are soft too
moderately hard, and sometimes contain noticeable amounts of iron.
Paragon Formation (Mpn)
Topography
Hard beds of sandstones within this predominately shale formation form
small cliffs or ledges.
Hydrology
The Paragon yields almost no water. Impermeable shale may hold water
in overlying sandstone
and conglomerate.
Slade Formation (Mn)
Topography
These limestone beds form steep hillsides and prominent bluffs in sides
of ridges and knobs that
are capped by Pennsylvanian rocks. In Powell county, 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 with 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 forms dissected slopes, massive siltstone forms cliffs, and limestone
forms ledges on shale
slopes. The Borden forms broad, flat valleys.
Hydrology
The Borden yields 100 to 500 gallons per day to wells in valley bottoms, and
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. It
forms 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. It
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 prominent ledges along hillsides.
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 in the Crab Orchard forms steep, dissected hillsides and broad,
flat valley bottoms. The
shale erodes readily below more resistant overlying limestone, forming
notches and recesses.
Dolomite beds form discontinuous ledges along hillsides.
Hydrology
The shale in the Crab Orchard yields almost no water to wells or springs,
but may yield small
amounts of water to wells in valley bottoms. Water is highly mineralized.
Dolomite beds yield
hard water to small springs.
Drakes Formation (Od)
Topography
The Drakes forms dissected upland areas, with slopes moderately steep
where underlain by
shale, and moderately undulating to gently rolling where underlain by
limestone. Steep and
cliffy slopes occur along large streams, littered with limestone slabs
left as shale beds weather
and wash away.
Hydrology
The Drakes yields 100 to 500 gallons per day to drilled wells in broad
valleys and along streams in uplands. It yields almost no water to drilled
wells on hillsides or ridgetops, but does yield water 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 enlarged
by solution. As a result, the limestone beds yield little water.
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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