I wonder why the central pale rock looks the way it does with its irregular furrows? It seems to be an odd one amongst the others in the dry stone wall.
This is one of a series of photographs that were taken of the dry stone walls beside the path from Rhossili village towards the Worms Head Causeway.
Jessica's Nature Blog 
The wall appears to be formed from an assemblage of locally formed and sourced glacial erratics from the Palaeozoic – a red “ Brownstone” conglomerate from the Devonian, limestone from the Carboniferous (Pembroke Limestone Group) and possibly even a quartzitic Sandstone called the Twrch Sadstone from the Marros Group (former Millstone Grit).
Putting on my geology hat (as I have been taught the script of the stones!), I’d say the furrowed limestone is a Gully Oolite Formation (Caswell Bay Oolite) which is a fine grained white weathered light grey limestone. The limestone is shallow marine in origin. As such the furrows probably represent the depositions bedding plane or palaeokarstic surface of when the limestone was exposed at the surface. The literal representation or record of a line in the sand of time.
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Those furrows do seem to have a story. Like wrinkles on a face. I do love looking at the details of these pictures. Thank you.
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That’s great, Chris. Thank you so much for your explanation. I have in the past tried to identify rocks in situ in Gower, but loose stones are more problematic for me, and I am always uncertain. I don’t think I have recognised Gully Oolite in context before although I know from the maps and books I know it is around. Thank you for enlightening me and the other readers.
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