To
log you will need to post a photo of yourself or your group with
the earth formation in the background
and in an email to the cache owner,
identify the oldest fossil bearing formation present,
along with the type of fossils and type
of rock they are found in.
Strata are the hard evidence of the passage of time
and changing climatic conditions in a given area. The rock types
can give clues as to an area being covered in shallow water, deep
water or glaciers. They can also give evidence to erosion or
deposition of sediments.
The geological display at
Schramm exposes layers of sedimentary rock ranging from Eudora
Shale and Stoner limestone from the Paleozoic Era, 542 million
years ago to Dakota sandstone deposited during the Cretaceous
period 146-65 million years, to the windblown Peoria Loess soil of
a more recent 1.8 million years ago.
The Paleozoic era strata are characterized by repeated cycles of
deposition of marine limestone and shale and in places non marine
sandstone and shale. Nebraska at this time period was a shallow sea
that varied in depth over the span of years. Limestone strata was
produced by remains of living organisms found in shallow, warm
waters while the shale strata are composed of particles of
preexisting rocks that have been deposited in deeper water that
didn’t support the calcium rich organisms that produced
limestone.
Towards the end of the
Cretaceous period this shallow inland sea retreated. Sediments
originating from the erosion of the Rockies, and carried by
watersheds across Nebraska to deposit alluvium or particles of
various sizes carried by running water and dropped when the flow
rates can no longer sustain movement of the
particles.
Glacial erosion during
the Pleistocene epoch created sands and finer particle silts, that
were carried by the winds to deposit what became the sand
dunes and Loess. Over
some areas this Loess was deposited to amazing
depths.
To
log this Earthcache you may post a
photo of yourself or your group with the earth formation in the
background (photo is optional) and in an email to the cache
owner, identify the
oldest fossil bearing formation present, along with the type of
fossils and type of
rock they are found in.
You will not need to wait
for a response to log the cache online, however logs not meeting
all of the requirements within a
reasonable time frame will be deleted.
Reference:
Schramm State Park Field Trip:
Sedimentary Rocks, Stratigraphy, and
Geologic History.
Dr. Lindsley-Griffin and Dr. R.J. Goble
With contributions from: Ms. Amy
Carter, Dr. P.C. Grew, and Dr. M. A. Holmes
Department of Geosciences,
University of Nebraska-Lincoln