Tête-à-Tête-Tête

Those marks were bioturbation – or in plain English, fossilized worm tracks. The rock was shale – I believe it was from the Chattanooga Shale that underlies much of Eastern Tennessee and was laid down during the Devonian – when plants started growing roots and fish started walking – while much of the area we live in was underwater.

The tracks are deformed by the contraction of the sediment that took place as it dried out.

Interesting further reading (pdf): read about experiments using artificial fishing lure worms and plaster…