The Devonian Period.
Warm, shallow seas covered Iowa during Devonian time (345-395 million years ago
These waters were home to numerous marine invertebrates including brachiopods, gastropods, stromatoporoids, and pelecypods (just to name a few).
Sediments from this time are present at Claybanks Preserve in the form of various rock layers.
The name “Claybanks” refers to the light-colored soft limey shales of the 375-million-year-old rocks bearing the fossils. These outcrops of soft shale and limestone found along the banks of the Winnebago River (originally called Lime Creek) are where the “Lime Creek Formation” was first described in the geologic literature and thus represent the “type-locality” for this formation.
The Lime Creek Formation is divided into three members: Juniper Hill, Cerro Gordo, and Owen.
The relatively soft limestones and shales of the Cerro Gordo and overlying Owen Members are exposed here, and the abundant fossils within these layers comprise the famous Lime Creek Fauna.
This unit is regarded as one of the premier fossil collecting beds in the United States.
Fossils naturally weather free from the shales and limestone every year.
Unlike other preserves...
the collecting of fossils is allowed at Claybanks
Here is your chance to apply what you have learned
and have some fun.
To receive credit for this EarthCache:
Visit Claybanks and find yourself a fossil.
(This EarthCache's posted coordinates are a good place to start your search, but based on personal experience, you can find them almost anywhere along the river.)
Using the pictures above, identify it.
Describe what you found in you log.
(What type of fossil is it, what size is it, what colour is it, etc)
And, in an e-mail to me. Answer the following questions.
The Lime Creek Formation is divided into three members.
Which of these three are not
exposed at Claybanks?
Northeast Iowa seems like a strange place to find invertebrate fossils.
What does their presence here tell you about this area's geologic past?
I would like to thank John Pearson of the Iowa DNR for granting me permission
to develop this EarthCache here.