The Jenkins Pound Gap is the first site in Kentucky designated
as geologically significant. Pound Gap is an opening in Pine
Mountain, a long linear mountain that runs north and south for
almost 125 miles along the Kentucky and Virginia border. Pine
Mountain spans three Kentucky counties: Bell, Harlan, and Letcher.
For a distance of nearly 90 miles no stream cuts through the
mountain, and there are no natural crossing points, making it an
effective barrier to migration and transportation. People had to
get over this mountain and would do that at the easiest spot to
cross. A fault bisects the mountain at Pound Gap, and weathering
and erosion have created a “hole in the ridge”. This opening made
it easier to cross the mountain there. It is this “hole in the
ridge” that provided the Transportation Cabinet with our beginning
to better roads in this area.
Just a few years back, a massive construction project took place
here on this mountain, the road was moved and tremendous amounts of
rock were moved to make way for US 23.
If you look up on the rock face you will see that there are
caves, the workers covered the entries with cement and rubble so
that nobody could access them. There is also a fault on this
mountain "there is a picture below" you will notice when you are
heading South Bound that on your right the rock goes from slanted
to straight up and down, this is due to a fault that runs through
the earth.
You may find many different fossils in this area; many large
ones were un-covered during construction. Geologists and professors
come from far away to see this gem of nature.
There is also lots of wildlife throughout the area; you may see
deer, turkey, ELK, BEARS, and lots of different birds.
During construction of the new section of US 23, a wonder of
nature was exposed. This wonder is known as the Pine Mountain Pound
Gap Thrust Fault. A Thrust Fault is a tear in the upper part of the
Earth’s crust along which one block of strata is pushed up and over
another block of strata. The collision of the North American
continent with Africa and Europe more than 275 million years ago
formed the Appalachian Mountains and the thrust fault at Pound Gap.
The exposed strata that we see today would normally appear about
2000 feet below the surface of the earth. The construction of US 23
in Letcher County has given students, geologists, residents and
tourists the opportunity to study the unique history and formation
of the Appalachian Mountains and the thrust fault that could not
have been seen otherwise. The fault that runs through this mountain
was formed many million years ago when the tectonic plates shifted.
In geology, faults are discontinuities (cracks) in the Earth's
crust that are the result of differential motion within the crust.
Faults are the source of many earthquakes that are caused by
slippage vertically or laterally along the fault. The largest
examples are at tectonic plate boundaries, but many small faults
are known to exist that are far from active plate boundaries. The
two sides of a fault are called the hanging wall and footwall. By
definition, the fault always dips away from the footwall. Faults
can be categorized into three groups: normal faults, transform (or
strike-slip) faults and reverse (or thrust) faults. For all naming
distinctions, it is the orientation of the original dip and
movement of the fault as it was active, which must be considered,
and not the present day orientation, which may have been altered by
local or regional folding or tilting. A normal fault occurs when
the crust is in tension. The hanging wall moves downwards relative
to the footwall. The depressed ground between two parallel normal
faults is called a graben. A ridge between two parallel normal
faults is called a horst. Low-angle normal faults with regional
tectonic significance may be designated detachment faults.
Fossils are the mineralized remains of animals or plants or
other traces such as footprints. The totality of fossils and their
placement in rock formations and sedimentary layers (strata) is
known as the fossil record. The study of fossils is called
paleontology. Fossilization is actually a rare occurrence because
natural materials tend to be recycled. In order for an organism to
be fossilized, the remains normally need to be covered by sediment
as soon as possible. However there are exceptions to this, such as
if an organism becomes petrified or comes to rest in an anoxic
environment such as at the bottom of a lake. There are several
different types of fossils and fossilization processes. Fossils
usually consist of traces left by the remains of the organism
itself. However, fossils may also consist of the marks left behind
by the organism while it was alive, such as the footprint of a
dinosaur or reptile. These types of fossil are called trace
fossils. Tentaculites found in a State Park in Albany, New York,
believed to have existed over 360 million years ago. The oldest
known structured fossils are most likely stromatolites. Believed to
be formed by the entrapment of minerals by mucous-like sheets of
cyanobacteria, the oldest of these formations dates from 3.5
billion years ago. Fossilized deposits of heavy carbon (acritarchs)
that are also indicative of earlier life (3.8 billion years ago)
are currently proposed as the remains of the earliest life on Earth
Be sure to go on up the mountain towards the VA side and on the
right you will see the fault, notice that it is a dark diagonal
crevice in the rock.
There are future plans for a rest area here on the mountain.
Hopefully they will have some plaques and information about this
marvel. As of right now, there aren’t any signs or plaques that
tell the story behind the cut-through.
What you learn from this cache will have been stated in the
cache page until I can persuade the County Action Team to place
some markers on the mountain telling about its history.
To claim credit for the find, please post a photo of you and the
mountain and answer these questions! 1. At the listed coordinates,
what is the geographical feature you are looking at in the rock? 2.
What colors are present in the rock? 3. Estimate the width of the
feature.
