Posted by: Alan Pitts | September 28, 2011

A trip to a Mississippian reef

Over the past two weeks, I’ve been working through a lot of the photos from my summer field camp in Ireland.

For anyone keeping score at home so far I’ve covered:

Today I’m featuring some great invertabrate fossils from a Mississippian-aged reef (about 340 million years ago).

Firstly, here is a photo of the field location, on the shore of Lough Mask in County Galway Ireland.  Lots of limestone, heavily jointed with an egg shell weathered topping.

I’ll just get right to the good stuff. Here is a giant colonial coral.

If you zoom in, you can see how the individual corals all radiate outwards, some of them in sort of “wiggly” fashion. This location had a great impact on me, I think because the exposures like the one above look so “alive”.  For myself as a geology student, it has at times been hard to connect with fossil remains of ancient organisms that dont exist anymore.  I dont think it is easy to look at a coral sample in a box and imagine it as a living thing.  Not like looking at the remains of a dog or a bird or a fish.  This reef really set some of these creatures to life for me. You can see how this was a biologically diverse and rich environment.

Here is another little colonial community

These are Siphonodendron, a colonial rugose coral that lived in warm shallow marine waters during the Carboniferous.  They were common in shallow seas beginning in the Ordovician and disappear by the Permian.

This next one is a different type of coral, a solitary rugose coral, Siphonophyllia.  And this is definitely the biggest rugose I have ever seen.  They are also called horn coral because they resemble the shape of a bull or sheep horn.  This one is like a Texas Longhorn coral.

Here is a nice cross sectional view of one you can see the internal tabulae structure.

This next one is not is big but is still pretty spectacular, I think.

This next one I’m pretty sure is a bryozoan of some sort.

The rock unit which these fossils are in is from the Mississippian or what the Irish would call the Carboniferous, the Visean period of the Carboniferous to be more specific.  During this time Ireland was positioned near the tropical latitudes and this location would have been a marine shelf environment.

Here is where I found some useful info on Irish Fossils.  After looking through some of the info there, I think I might have just enough to earn my Irish fossils geology merit badge last summer. I think I found nearly all of them.



  1. Thanks for this and the Giants Causeway post. Your selection of photos and comments help me understand the units and how they formed much more clearly.

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