Geo-pic of the week: Graptolites

 

Graptolites

This is a picture of shale, collected from the Womble Formation, near Lake Ouachita State Park, Arkansas.  The photo shows examples of the, now extinct, Graptolites: fossilized colonies of tiny marine animals.

There were many types of Graptolites.  Some were attached to the sea floor, like corals, while others floated in the water, like plankton.  The feather-shaped fossils pictured here are actually the nests in which the animals lived.  Each tooth-like tube, on the edges of the nests, housed a tiny animal.  Several of these nests would be linked together into a larger colony.

At one time the oceans were full of Graptolites, but by about 300 million years ago they died out for unknown reasons.  Because they were abundant, widespread, and continually evolving, Graptolites are important fossils for dating ancient marine rocks. 

To download a copy of our self-guided tour of Lake Ouachita geology, click here http://www.geology.ar.gov/pdf/Lake%20Ouachita%20Geologic%20Float.pdf

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