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NO NIGHT CACHING!
Indiana Limestone
Earth Cache
This should be a quick
Earth Cache that will take you to the Beautiful
campus of the
University of Evansville. Many of the building here are built
from Indiana
Limestone. However the posted Coordinates will take you
to the example I am
wanting to show you.
The Salem Formation
(a.k.a. Indiana Limestone) crops out along a thin,
irregular arcuate band
in south-central Indiana (Monroe and Lawrence
counties). Most
quarries lie between the cities of Bloomington and
Bedford.
Quarrying of Indiana
Limestone began in 1827 with the opening of the
Richard Gilbert
Quarry. The quarried stone was produced for local use
only prior to the
building of railways in the 1850's. However, by 1900,
Indiana limestone
represented 1/3 of the total U.S. dimension limestone
industry, and
increased to 80% by 1920. There are currently 9 active
quarries that produce
76,000 cubic meters of Indiana Limestone each
year.
The limestone is soft
and easily worked when quarried, but once the
quarried rock dries it
becomes case-hardened, that is, its surface
becomes harder and
more resistant to weathering. Indiana Limestone is
a freestone, which
means that it has no preferential direction of splitting.
It can be planed,
turned on a lathe, sawed, and hand worked, making it
highly versatile.
Where quarried, the
Salem Formation varies from 8 to 18 meters (25 to
60 feet) in thickness,
and is unusually massive (i.e., lacks partings and
stylolites). For a
rock, the Indiana Limestone is chemically pure and
consistent, being
composed of >97% calcite. The combination of these
physical and chemical
characteristics make the Indiana Limestone
well-suited to
building because:
• It is more
durable than a typical limestone
• It can be cut
into very large blocks
• It can hold
fine detail when carved
GEOLOGICAL
FEATURES OF THE INDIANA LIMESTONE
The building stone
quarried from the Salem Formation consists of
light-grey to
bluish-grey limestone (calcarenite) that has oxidized locally
to a light tan. It is
medium to coarse grained, well sorted, and porous. It
consists mostly of
small fossils and fossil fragments.
The most abundant
fossil is the foraminiferid Endothyra baileyi that is up
to 1 mm in length.
Foraminiferid (forams for short) are marine
single-celled protists
with shells that are commonly divided into
chambers which are
added during growth. Endorytha appears as small,
simple, smooth,
ellipsoidal grains. The complex, chambered structure of
its shell (or test) is
apparent only under the microscope.
Fragments of bryozoan
are also common in the Salem Formation.
Bryozoans are tiny
aquatic organisms (rarely larger than a millimeter)
that live in colonies
of interconnected individuals. Some bryozoans
encrust hard surfaces
such as rocks or shells. Other bryozoans formed
tree-like branching
colonies. The most abundant bryozoans in the
Indiana Limestone
formed fan-like colonies that left behind lacy,
net-textures fossils.
Each window-like hole in the net once housed an
individual bryozoan
animal. "Fenestra" is latin for "window", and so this
type of organism is
refered to as a fenestrate bryozoan.
Other fossils grains
that can be found commonly in the Indiana
Limestone include:
• small
gastropods (snails)
• disarticulated
disc-shaped ossicles from the stems of crinoids.
• pelecypods
(scallops) with radiating ridges on their shells
• brachiopods
ENVIRONMENT OF
FORMATION
During the Middle to
Late Missisippian (335-340 million years ago), most
of what is now the USA
was covered by shallow seas that straddled the
equator. Limestone
accumulated on the seafloor below these warm,
tropical waters.
The Indiana Limestone
formed far enough offshore that very little
continentally-derived
siliciclastic sediment was available to mix with the
carbonate sediment
that was forming in the immediate area.
Despite being 10's to
100's of kilometers offshore, the water was shallow
enough for waves to
move coarse carbonate sand across the seafloor.
The constant wave
action washed away the smallest particles, whereas
the larger fossils
were battered and broken. The result was a rock
consisting of well
sorted grains that consist of small fossils and fossil
fragments.
Like modern-day fan
corals, fan-like fenestrate bryozoans lived in quiet,
low energy
environments. Thus the abundant fragments of these fossils
must have been
transported from their original setting, but could not
have been moved too
far or else these delicate fossil fragments would
have been completely
destroyed.
To Qualify for
this cache answer the following questions:
1) Rub your hand over
the Limestone facing. Is it extremely rough, rough,
smooth, or
polished?
2) Look closely, what
do you see about head high on both sides of the
door?
3) Why is Indiana
Limestone good for construction of buildings?
4) Tell me what type
of fossils are clearly visible.
5) Post a picture of
you and your GPS at the building (not required but
appreciated).