Red Wharf Bay

Rather than trawling through the waters of Red Wharf Bay as we did yesterday aboard The Prince Madog, today we were there on the ground level hunting for fossils. The Bay lies in the center of a large transform fault (define: two land masses sliding against each other rather than apart or together), and because it was low tide we could walk along the fault. Our main destination was an outcrop of rock that dates back to the Carboniferous period (350-300 million years ago). The rocks were a bit overgrown but we bushwhacked our way through the vines and ventured to less plant-dominated areas.




During the Carboniferous, the (now) U.K. resided in tropical latitudes and was partially submerged due to global sea level rise. The oceans at this time were very diverse and contained a ton of interesting organisms; some are now extinct, but others are still around today.


The most common fossils we found were crinoids. They belong to the phylum echinodermata (the same as sea stars and urchins) and are still alive today.  Despite their sparse abundance now, crinoids were prolific during the Carboniferous.

At the apex of a long stalk, crinoids have feathery arms arranged around a central mouth. The stalks are made up of columnals, small round disks that are stacked on top of each other. We saw these disks fossilized everywhere; sometimes they were dotted here and there on the cliff face and sometimes they covered the whole rock face.  If you look closely, you can see some of the small fossils below:


We also discovered some fossilized coral heads (bonafide evidence that this place used to be underwater) and as brachiopods, which were also very common during the Carboniferous. Brachiopods have their own phylum and many are still here today.  They look similar to clams but have shell valves of different sizes and a pedicle, or short stalk, that enables them to attach to a hard surface.


The photo on the right show a cross-section of a brachiopod (using a ₤2 coin for scale). You can clearly see the difference between the two valves.

On that particular day, the rocks at Red Wharf Bay were simply part of a typical rocky coast landscape.  But take a second to think about it.  We were standing on an ancient ocean, touching things that were over 300 million years old, and catching a glimpse of the life that used to flourish there! So cool!

If geology like this is your thing, keep an eye out for a post later about our trip to the Snowdonian mountains; there are more rocks to come!

About David Malmquist

David Malmquist is the Director of Communications at the Virginia Institute of Marine Science, College of William and Mary.
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