While we were on Islay, Tom had asked me to photograph any 'interesting' rocks when in the north of the island. He explains here what these rocks represent and their importance:
In the north of Islay, there are are some relatively small sections of coast where unusual rocks are exposed. These rocks are the Member 3 of the Bonahaven (Bunnahbhain) Dolomite Formation. These rocks were deposited, as sediment, in the Neoproterozoic- the name given to the period of time around 700 million years ago. During in this time the first multi-cellular life began, that would eventually give rise to us.
These rocks were deposited in a lagoonal/intertidal environment from silt and sand. Within these sediments algae lived, photosynthesising and coagulating sediment- these are stromatolites. Modern day stromatolites can still be found in areas such as Hamelin Pool, Australia and the Bahamas. These ancient life forms are preserved in their life positions in the rocks of north-east Islay.
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| Exposures of interbedded metasandstones and metadolmites. |
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| Some stunning stromatolite bioherms (large rounded forms) with strongly laminated upper sections. |
These represent the earliest life in the world, and possibly represent life on other worlds in the universe. The stromatolites on Islay are some of the earliest fossils in the UK and are a fascinating and crucial key to our past.
For a previous blog on these stromatolites- click here- and for more information visit:
https://islaygeology.org/ or https://www.islayinfo.com/islay-geology.html.
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