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Rosselia – or Rosselia socialis – is a trace fossil that’s common to rocks deposited in a variety of shallow marine environments such as estuaries, tidal flats, lagoons, etc.. This picture was taken in a quarry in the Pennsylvanian Bloyd Formation, near Greers Ferry, Arkansas. Rosselia is a funnel-shaped burrow with concentric cone-like layers, and a sandy plug near the center. The picture shows a side view, or cross-section, of several burrows.
Like many trace fossils, Rosselia was made by a soft-bodied animal that was rarely if ever fossilized. We only know it existed because of the burrows it left behind. They may represent places an animal lived, fed, or perhaps both.
One theory suggests the burrows were occupied by worm-like animals that fed by filtering nutrients from sediment, then excreting the sediment outward around their bodies in concentric muddy layers. When new beds of sand were deposited, the animal would crawl to the top of the sand bed and make a new burrow; this behavior is clearly evident in burrows at the center of the photo.
Be sure to check out more pictures of Rosselia here!
Just wanted to let you know that the Statemap 2014-15 field mapping project has resulted in the publication of three new geologic maps. These are the Parma, Prim, and Greers Ferry quadrangles. Reduced images are posted below. These should be available as .pdfs on our website in the near future. I’ll keep you posted!
Greers Ferry Quadrangle
Also, I would like to thank the many people who helped with data collection in the field this year, without whom this project would have been impossible.
Andy Haner Danny Rains
Angela Chandler Stefanie Domrois
Doug Hanson Ty Johnson
Now it’s off to the Brownsville quad for next year!