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I'm a geek. I love sciency geek, especially palaeontology. Geology and MTB sit well together. Yesterday I was up in Gwynedd meeting family and I was given a HMSO guide to the geology of the Welsh Borderland. Nothing special I thought, I'll browse through it later.
Published in 1970 the content is now somewhat dated but oh my word, as a publication it's a work of art. Monochrome and colour photographic plates, surveys, cross sections, colour and b&w maps and plans, gorgeous illustrations of fossils and all 120 pages fully indexed too. Price is 8s 0d (40p) NET. At current rates, £7.75.

We carry in the car a 1980's 'The waterfalls of Scotland' book. Great images, hand drawn maps, author clearly visited every fall in the book... Great on our various travels for some unusual walks.
On my shelf I have Richard Gilbert's The Classic Walks, The Wild Walks and Big Walks. Same as above, big, beautiful colour and black and white plates, pictures that you would die to have taken and fabulous detailed routes with real timings that have been intimately recorded and relayed through the book. There are shots of Scottish winters that we will never see again, a single solitary vehicle parked in torridon, single track roads that are now long gone. Magical stuff.
I picked them all up for pennies really, jumble sales and second hand book shops. These days something similar would be 50 quid new I reckon.
What you've got there Ambrose is roughly equivalent to the British Geological Survey's Geological memoirs. While they won't do one that covers the Welsh borderland, there is one memoir for every OS 1:50,000 map sheet.
Some of the old ones haven't been updated since the sixties and are dry reads but some of the newer ones (Nottingham as an example) are really interesting.
They're all available online for free but you can get a physical book too.
https://pubs.bgs.ac.uk/publications.html?pubID=B06066
I've just had a scout about on the internet and it looks like that Welsh Borderlands guide was produced by the Natural Environment Research Council (which still exists today) as a guide for people working in radioactive waste disposal! There's a modern version of it that's only about 20 pages long.
@munrobiker, I know, I've a bunch of them for my bit of Wales. They're far more detailed and as above, much drier.
The Merthyr one is OK though, once you get away from the Coal Measures.
I didn't know that they are online, many geeky thanks for the heads-up.
Also here, Cold Climbs and Hard Rock as well as those above. And additionally, Rock Climbing in Britain inc. Billy Bollweavil on Ordinary Route, Idwal 🙂
