The Salem Formation: Indiana’s ace in the hole EarthCache
Indotguy: Archived by owner.
The Salem Formation: Indiana’s ace in the hole
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Welcome to the heart of Limestone Country. The coordinates waypoint
a historical marker dedicated to the subject at hand. Free parking
is available.
Geology –
The Salem Formation is the geologic name for a carbonate unit known
commercially as Indiana Limestone, Bedford Limestone, or Salem
Limestone. Indiana Limestone is a high quality Mississippian age
stone of very uniform texture and grade that occurs in
exceptionally thick beds (60 to 100 feet). It crops out along a
thin, irregular band in south-central Indiana through Monroe and
Lawrence Counties and has gained world wide acceptance as a premier
dimension stone. The stone is soft and easily worked when quarried,
but once the rock dries it becomes harder and more resistant to
weathering.
Sediments which formed the Salem Formation were deposited during
the middle to late Mississippian period (335-340 million years ago)
when most of what is now the U.S.A. was covered by warm, shallow,
tropical seas that straddled the equator. Salem Limestone formed
far enough offshore that very little continentally-derived
sediments were available to mix with the carbonate sediment that
was forming in the immediate area. 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.
History –
The first recorded use of Indiana limestone as a building material
was in 1819 where it was used in the foundation and window sills of
the original Monroe County Courthouse. Quarrying of Indiana
Limestone began in 1827 with the opening of the Richard Gilbert
Quarry in Stinesville, Monroe County. Prior to the railroad, quarry
operations supplied stone mainly for bridge piers and chimneys.
Construction of the railroad led to the opening of many new
quarries during the 1850’s and 1860’s, both to serve
the construction needs of the railroad and also to provide building
stone for cities such as Chicago, Cincinnati and Louisville. By
1900, Indiana Limestone represented 1/3 of the total U.S. dimension
Limestone industry and increased to 80% by 1920. There are
currently nine active quarries which produce approximately 76000
cubic meters of Indiana Limestone each year. The Empire State
Building in New York City and the U.S. Holocaust Memorial and
Museum in Washington, D.C. are clad in Indiana Limestone.
Stratigraphy –
Geologist use a chart known as a General Stratigraphic Column to
help visualize the structural relationship between the various rock
unit members, formations, and groups; thicknesses, lithologies, and
units of geologic time. The Indiana General Stratigraphic Column
below shows the Salem Limestone (Ls.) Formation in the upper level
of the Sanders Group.
Logging Requirements –
1) Email Indotguy with
answers to the following questions. DO NOT post the answers
with your log!
a. According to the historical marker at the posted
coordinates,Limestone quarries have been in continuous operation
here since approximately what year?
b. Name the Limestone Formation which lie directly above and
directly below the Salem Limestone Formation.
c. Name the Significant Member of the Borden Group.
2) Optional - Upload a photo with your log showing you and your GPS
at an obvious Limestone Country location (town sign, highway rock
cut, etc.).
Note - Correct answers are required to log a Find.
Additional Hints
(Decrypt)
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