SEMO Fossil Club collecting Owl Creek formation
Cretaceous
Ardeola, Missouri
Dr. Bruce Stinchcomb had extended an invitation to
the SEMO fossil club
to collect on his property in S.E. Missouri. We collected from the Owl Creek
formation, a mudstone deposited in the Mississippi Embayment at the
end of the Cretaceous. The formation has a very diverse fauna, but are
very delicate.
Click on pictures to Magnify
1
SEMO fossil club members working through the deposit
2
3
This beauty of a centipede scurried by
4
I found this large clam, notice it is at 90 degrees to the bedding plane
5
Large clam from previous picture removed from deposit.
Promptly dropped and broke into two pieces after photographing.
6
One small shark tooth was found
7
This is a section of a gonatitic ammonite, which will be about 70%
complete when reassembled, about the size of a small dinner plate.
8
The further we get into the deposit, the better preserved the
specimens are. This little echinoderm should clean up nicely.
9
Ammonites are common, some are starting to show a little nachre
10
Discoscaphites iris
Dr. Stinchcomb said that this was the best he had seen
from this area, high praise indeed.
11
5" razor clam ready for re-assembly
Brent Ashcraft
Discussion
Lovely haul of goodies Congrats!!
Just a quick correction: the final photo is a pen
shell (Pinna sp) as opposed
to a razor clam. e.g. http://en.wikipedia.org/wiki/Atlantic_jackknife_clam
any of several different species across several families.
Pinna is fairly common in the Cretaceous of Texas,
particularly in the
Goodland Fm. (lower Albian). Usually only small pieces though.
I have only found one pinna-like fossil in all my days and from a Devonian
fossil
bed no less. These are the source of the basile textiles -- golden thread
fibers
used to knit golden gloves and socks, now surmised to be the source of the
golden fleece myth.
Elton
Nice to see the field trip photos
In western Alabama the equivalent formation is the
Prairie Bluff Chalk, which
can be very fossiliferous. One of the most intriguing exposures, now closed
to
the public due to the discourtesy of a professional geologist, is in a creek
bed.
Above typical Prairie Bluff, there is another chalky layer - actually, a channel
deposit into the Prairie Bluff, and of Paleocene, and it is loaded with typical
PB fossils. At the time I saw it, in the late 1960s, it was thought to be
a
storm deposit, but when I learned about the Yucatan impact, I knew instantly
what it was - a tsunami deposit!
In eastern Alabama the equivalent strata are called
the Providence Sand.
I know nothing about this formation except its name.
Kenneth Q.
If the echinoid (photo 8) was here in Dorset I would have called it a
Micraster SP, either cortestudinarium or coranguinum
(Upper Chalk)
Doreen
I would guess that's a Linthia sp., (photo 8) probably L. variabilis,
which is
pretty common in rocks of the same approximate age in the central Gulf Coast.
They're all spatangoids, what we usually call heart
urchins. Some are pretty
distinctive in appearance, but most look very much alike. Brent's specimen
is
pretty typical in size for Linthia (about 1 in. or 25mm); most of the Micrasters
I'm familiar with are probably at least twice that size full-grown. Also,
most
Micrasters taper front-to-back to a fairly narrow posterior, which makes
them even more heart-shaped than many other heart urchins.
We have quite a few different types of spatangoids
in our Albian (Lower
Cretaceous) rocks around here, and they're pretty hard to tell apart, so
naturally their published taxonomy has been pretty messed up for over
150 years!
Frank
Fossils
of the Owl Creek Formation
Achive of fossils found to-date at this locality
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