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Alluvium (Qa)
Topography
The alluvium forms terraces and narrow floodplains of varying width
along streams.
Hydrology
The alluvium yields almost no water to drilled wells, and small quantities
to dug wells.
Borden Formation (MDbb)
Topography
The Borden forms broad, flat valleys; the shale forms dissected slopes,
and the 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, 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, flat upland surfaces, and
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.
Crab Orchard Formation and Brassfield Dolomite (Scb)
Topography
Shale 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
These formations yield 100 to 500 gallons per day to wells in broad valley bottoms,
but almost no water to wells on hills. They do 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.
Drakes Formation (Od), (Odb) / Bull Fork Formation (Ob)
Topography
These formations form gently to moderately rolling uplands, except along
large streams, where there is considerable dissection; slopes are 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
These formations yield 100 to 500 gallons per day to drilled wells in
broad valleys and along streams in uplands, but almost no water to drilled
wells on hillsides or ridgetops. They do 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. 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 rocks form 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
These rocks yield 100 to 500 gallons per day to drilled wells in broad
valleys and along streams in uplands, but almost no water to drilled
wells on hillsides or ridgetops. They yield 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 forms prominent ledges in steep slopes and bluffs along
large streams.
Hydrology
The Garrard yields 100 to 500 gallons per day to drilled wells in valley bottoms,
but almost no water to wells on hillsides or ridgetops and almost no
water to springs. The well-cemented siltstone and fine-grained sandstone
do not provide many openings for water. Water is hard.
Kope Formation (Okc)
Topography
The Kope forms narrow, steep-sided ridges with narrow valleys between.
Hydrology
The Kope yields 100 to 500 gallons per day to drilled wells in valley
bottoms, but almost no water to drilled wells on hillsides or ridgetops.
It does yield water to small springs. Water is hard in valley bottoms,
and may contain salt or hydrogen sulfide.
Clays Ferry Formation (Okc)
Topography
The Clays Ferry forms broad, flat valley bottoms along the Licking River
and a few larger tributaries in the county.
Hydrology
The Clays Ferry yields 100 to 500 gallons per day to wells drilled in broad
valley bottoms, and yields water to small springs. Water is hard and
may contain salt or hydrogen sulfide.
Lexington Limestone (Ol)
Topography
The Lexington lies in valley bottoms along the Licking River.
Hydrology
The limestone yields more than 500 gallons per day to wells in stream valleys
and as much as 150 gallons per minute in places. 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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