Lost River - Karst Information Portal

that time. Locally, they are rarely preserved,
except as teeth and scales. The armored fish
related to the giant arthrodire and cartilaginous
fish-like sharks, and bony fish like coelacanths
(lobe finned fish) developed in the Middle
Devonian, therefore well-preserved remains are
scarce. The needle-like teeth of one coelacanth
can be found in the youngest layers of the
Jeffersonville Limestone.
The overlying Devonian-age North Vernon
Limestone is found on the far end of Goose
Island, near the upper gates of the dam. The
best exposures of this strata are northeast of
the Falls near Charlestown and Sellersburg.
This formation has a different variety of fossils
compared to the underlying Jeffersonville
Limestone. Crinoids are more abundant and
diverse. Corals are still common, but less
diverse. Mollusks, especially snails and clams,
are more common. Echinoderms include
crinoids and blastoids. Crinoid stalks have
spine-like flanges for hooking to the substrate,
which kept the animal from being swept away
by currents. Most other crinoids and blastoids
had “rootlets” (called cirri) radiating away from
the base.
Mollusks include snails, clams, and
Travel to Lost River along U.S. 150,
Up the Knobstone, and across the
Mitchell Plain along the Buffalo Trace
Fr o m t h e Fa l l s o f t h e O h i o , w e w i l l
retrace our Louisville Riverfront path back to
Interstate 64 and up the Knobstone Escarpment
near Floyds Knob, traveling a short distance
across the Norman Upland to the U.S. 150
interchange. We will then travel northwest on
U.S. 150 across Norman Upland and the Mitchell
Plain to Hardinsburg. The total distance is about
34 miles. See Figures 36, 37, and 38.
The Knobstone Escarpment is a classic
regional erosional feature with up to 500 feet
of relief developed upon resistant interbedded
shales, siltstones, and sandstones of the Borden
Group and the Kinderhookian Series rocks.
The western dip slope border of the Knobstone
Geology Field Trip
scallops. Most clams are not visible in the
living position because they lived buried
in the sediment, with only their siphons
sticking out. Their empty shells littered the
sea floor, just as they do today. Brachiopods
are among the most abundant animals in
the North Vernon Limestone. A type called
“spiriferids” are exquisitely preserved in
some layers, and some show rare internal
structure. One trilobite, called Phacops, is
common in this formation. It can found flat
or enrolled. Trilobites enrolled when they
sensed danger. A storm or a shift in sea floor
sediment might bury them. Most Devonian
trilobites have multi-faceted eyes similar
to an insect’s. These creatures may have
been the first organisms to see the world
around them clearly and in color. A large
fish was Cladoselache, a primitive shark. The
overlying Beechwood Limestone contains
arthrodire (armored) fish plates, exceeding
6” across. The fossil fish bone fragments
are black, but turn blue upon exposure to
sunlight. They are most common where
limestone rock changes to black shale. The
thin layer is called a “bone bed.”
Escarpment is the Norman Upland, grading
into the Mitchell Plain where Borden Group
clastics are increasingly overlain by the mid-
Mississippian-aged limestones of the Ramp
Creek, Harrodsburg, and Salem limestones
from east to west. State Road 150 crosses many
surface streams in the Normal Upland. State
Road 150 follows the historic Buffalo Trace
and is often built along some ridge tops of the
Mitchell Plain, offering the tourist many scenic
vistas, especially across the headwaters valley of
the Blue River. The highest Norman Upland
elevations far to the east are underlain by the
argillaceous, poorly consolidated quartz sand,
Tertiary aged, Ohio River Formation. The
Mitchell Plain begins near Galena in western
Floyd County and is well developed about
where U.S. 150 crosses from Floyd County into
Harrison County near Greenville.
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