UKC

Does anyone know about the geology of the purple rock layer at the base of the Grey Face (where Ethos, Woodentops and Mombasa are) at Carreg y Barcud? Its really weird rock! it looks scored in a diamond pattern (like pork crackling, how very topical) with a slightly harder surface layer, causing really knobbly rock but in this weird crackling pattern. To me it looks like an ancient layer of dried out mud that cracked as it dried and was then tilted up vertically. my buddies reckoned that all the rock at barcud is in layers like that, but its only at the bottom of the grey face that this layer is exposed. Does anyone have any actual knowledge, as opposed to our uninformed guesses? Id love to know how it got like that!

In reply to pebbles:
The rock is sedimentary sandstone so probably is mud

In reply to pebbles:
I'm not familiar with the area nor a geologist but what you describes sounds like slickenside - check Wikipedia - given that Barcud I assume is formed by tilted bedding planes this seems plausible to me.

In reply to Stig:
no, its like a real criss cross diamond scoring - literally like pork crackling or a tray of baklava, but in purple stone - imagine this http://preview.tinyurl.com/ohghvu2 but in purple rock. score lines were probably about 4" apart, and the purple layer was about 7m high. (ie the height of the first pitch if you split the route to use the suggested high tide belay) I wish I'd taken a photo now. It was so unusual that when I went round the corner to get a look at the route I muttered in surprise. Although I then absolutely HAD to do the route just to climb on that rock!

In reply to pebbles:

If it's this: https://ukc2.com/i/181968.jpg

Then its a fracture system

In reply to pebbles:

never been there, but from what you describe it could be dessication cracks. a layer of mudstone which litterally dried out a cracked into polygon shapes. these cracks then get filled in by sand or a coarser mud when the surface is re-submerged, effectively beccoming fossilised.

but if you are talking about something close to the previous posters photo then its nothing particularly interesting, just an artefact of how that area of rock has weathered as it apears to be near the high water mark.

In reply to Webster:

yeah thats it. oh boo, I thought it must be some really interesting process!!!! it looks very weird when you see it up close anyway. (and obviously in my memory it had got weirder as I fixated on the criss cross effect). Oh well , thanks. No pixies or alien intervention then ;-D.