Christensen Mastodon Bog EarthCache
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I remember visiting the site of Christensen’s Mastodon Pond with my
family, and being amazed at the work that was taking place, and
excited that something this old was so close to my home.
The location of this earth cache is located on a busy road, so
please take care in parking. Use land-owner’s driveway.
Mike Christensen, a Hancock County resident, discovered some bones
in a boggy field on his farm in late 1976. Dr. Arthur Mirsky
identified the bones as part of a now extinct ice-age mastodon, and
expressed an interest in excavating the rest of it.
The excavation project began in late March, 1977 and ended in early
October, 1977. The mastodon bones recovered actually were from two
individuals: a nearly complete skeleton of an adult female mastodon
and fewer bones from a juvenile male.
Several carbon dates taken on fossil wood that occurred in the same
two layers that contained the bones, indicate that the mastodons
lived in this area about 13,500 years ago. Fossils of other animals
were also excavated. From a scientific perspective, the most
important was the discovery of the antlers of a caribou, the first
known occurrence of caribou in Indiana, although fossils of this
animal previously have been found in the states that surround
Indiana.
Also, pollen evidence from the bone-bearing layers suggest that
central Indiana at this time was part of an open boreal,
spruce-dominated forest, perhaps transitional to a tundra
environment, which is supported by the vertebrate fossils. During
the next several thousand years, as the glaciers and their adjacent
boreal environment slowly retreated to northern Canada, the present
climatic environment of Indiana became established.
During the excavation, at the end of each day, the various bones
that were recovered were taken to the Children's Museum, where they
were treated to help preserve them from drying out and cracking. At
the end of the excavation, Dr. Graham began the arduous process of
re-assembling the bones of the nearly complete adult mastodon. The
missing bones were restored by the Field Museum in Chicago, where
substitute bones were reconstructed out of fiberglass. The
completely re-assembled Christensen Mastodon was then placed on
permanent display at the Children's Museum, and it can be seen
there now. At the same time, the skull, ribs, and vertebrae of the
second (juvenile) mastodon, along with fossils of several other
animals found with the mastodon, were put on display in the IUPUI
University Library.
Around 20,000 years ago, much of Indiana from Michigan south to
Martinsville was covered by a glacial ice sheet many hundreds of
meters thick. Then the ice began melting back northwards until,
about 10,000 years ago, the glacier was gone from the state. As the
ice retreated, it left behind many areas that became bogs, one of
which was the boggy field on the Christensen farm. Excavation of
this bog revealed 5 layers, which from bottom to top, are: (1)
light-colored outwash sand that had been washed out from the
retreating glacier, (2) black, laminated lake beds, with no
apparent fossils, (3) yellowish, silty laminated lake beds, with
mollusk shell fragments, some wood, and some bones of mastodon and
fish, (4) dark-colored massive peaty clay, with many mollusk shell
fragments, much woody material, and most of the mastodon bones, and
(5) light-colored surface deposits of slopewash, with no
fossils.
The property owner has given permission for visitors to park at
the entrance of their driveway and ONLY stand at the edge of the
driveway and take a picture from that point of the pond. This is
all that is left from the excavation of the mastodons.
To claim this cache you must estimate how many acres the pond
covers. You will send me an email with the acreage requirement. You
must also take a picture of the pond, with a human in the picture
along with your GPS displayed. If you are unable to take a picture,
you will email me the number on the landowner’s mailbox. Do not
post either pieces of information in your log. This cache may be
visited only dawn to dusk. NO NIGHT CACHING! SCHOOL BUS DROPS OFF
SOMETIME AROUND 2:40, M-F AND TURNS AROUND, SO PLEASE DO NOT BLOCK
THE DRIVEWAY AT THIS TIME. PLEASE BE RESPECTFUL OF LAND-OWNERS.
Information provided by Arthur Mirsky, Ph.D., Department of
Geology, IUPUI
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