Bluefield Formation

On Friday Brett, Tim, and I headed to West Virginia to look for potential fossiliferous outcrops. One of our stops was along a railroad cut near Kellysville, where there is an exposure of the late Mississippian Bluefield Formation (~325 Ma). The Bluefield is primarily a sandstone, but there are thin beds of limestones that contain some fossils, and one of these beds is exposed along the railroad cut.

There were several different types of brachiopods, including these tiny examples (terebratulids, I believe):

There were also a few examples of apparent rugose corals (all the examples we saw were cut in section like this):

But the dominant fossils were bryozoans, with several different taxa present:

One thing that I was initially unable to identify were these thin parallel lines in the sediment:

Close examination of other specimens showed that these are cross sections of complete colonies of the spiral bryozoan Archimedes:

Here’s a reconstruction of Archimedes (model at the State Museum of Nebraska):

Archimedes is a delicate bryozoan, is is thought to have been mainly present in low energy, protected environments.

We collected a number of samples for the museum, and Brett collected some for her teaching sets at Patrick Henry Community College. Over the fall, we intend to make numerous day trips into the Appalachians to look at additional Paleozoic localities.

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