Last year I had the pleasure of going on a four-day residential field course as part of an Open University geology module (SXG288); one of the sites we visited had a spectacular feature that might be of interest to those who appreciate sand in all its forms.
The site was Bowden Doors in Northumbria (NU 072323), a long, west-facing crag of Fell Sandstone, 3-8m high, a favourite of both climbers and geologists. The sandstone is derived from the erosion of rock above what is now the Southern Uplands of Scotland and the sand was carried south-eastwards by a braided river system during the early Carboniferous period. There are several unusual geological features that I won't reveal (to avoid spoiling future visits by OU students), but the thing that impressed me most was the 'Sandwave'. I was sure Michael would know of this - but he didn't and he invited me to write a guest blog about it.
Inevitably the pictures I had weren't suitable so I revisited the crag some months later: once home I discovered that none of the pictures had come out - or had disappeared into the digital ether. A third visit was a bit more successful.
Looking south-east at the northern end of the crag: it is capped by an impressive quiff, not of hair but of sandstone - the 'sandwave'. (Note person on extreme right of the picture for scale).
Here's another view - with climbers in the distance:
Although it resembles a 1950's quiff, it is really the eroded remnants of the last remaining layer of cross-stratified sand, now compressed into stone, that has resisted the Northumbrian weather more successfully than the lower layers.
So, an impressive location and an interesting contrast to some of the coastal sites we visited where there are some fantastic fossils and lots of other geologically interesting features. The scenery is good too!
[John and Ann Lackie are friends who live on the borders of the Lake District – Ann, under her author’s alter ego of Ann Lingard, has written for this blog in the past. The topic of the ‘sandwave’ arose during a rambling conversation over the course of a delightful pub lunch in the heart of the hills earlier this year. Thanks for this, John - I'll have to make a pilgrimage myself! For more on cross-bedding see this old post.]