27 June 2016

Small faults in upper Old Red Sandstone, Dunbar, Scotland

Posted by Callan Bentley

Dunbar, Scotland, is a nice little seaside town that also happens to be the birthplace of the conservationist John Muir. My family and I have been based out of here this week on our European geological GigaPan expedition. But on our first morning, upon visiting Siccar Point (which is nearby), I threw out my back, and spent most of the next two days recuperating. I did manage a short walk to the beach in a cove on the northwest side of town.

My son instantly keyed in on the puddles, and took his pet centipede there to play in the water:


The clean exposures of the bright red sandstone there caught my attention, and I then did my own ‘keying in’ – this time to the many small offsets in the primary sedimentary layering. They are exquisite!


According to the local geological map, these rocks are the Devonian- Mississippian upper portion of the Old Red Sandstone – the same stuff that caps the unconformity at Siccar Point.


It was apparently quite disturbed by the intrusion of a collection of igneous masses at ~345 Ma. Many of these small faults looked to me like soft-sediment deformation, so I don’t know that I would have invoked volcanic molestation if I hadn’t read about it, but regardless, they are a delight to behold. I think the primary reason I fell in love with structural geology is that structures like these are just plain beautiful.