This is a fabulous image -- Fedchenko Glacier in Tajikistan. The biggest glacier outside of the polar regions -- 70 km long.
This isn't too bad either -- Bering Glacier in Alaska:
How much do we know about Stonehenge? Less than we think. And what has Stonehenge got to do with the Ice Age? More than we might think. This blog is mostly devoted to the problems of where the Stonehenge bluestones came from, and how they got from their source areas to the monument. Now and then I will muse on related Stonehenge topics which have an Ice Age dimension...
This isn't too bad either -- Bering Glacier in Alaska:
But times have changed. When we started, Preseli District Council was our local government admin area, with its HQ in Haverfordwest. Then came Dyfed CC -- it came and it went away again. Patterns of holidaymaking have changed, people now get their information via the web, and Visit Wales and Visit Pembrokeshire use all the latest marketing techniques to compete with other tourism areas to attract future visitors. Small "regional" or "sub-regional" marketing exercises don't really have a role any more. So effectively the PTA has become redundant, having done its job over many years -- just like Eco Centre Wales, which I founded back in 1980 and which promoted energy conservation and renewable energy for 35 years until it was wound up in 2015.
Now, of course the branding label has been stolen from us -- we have the huge Bluestone National Park holiday resort in mid-Pembrokeshire, Bluestone Brewery and assorted other bits of branding as well, not to mention Australia and the USA, which have their own "bluestone branded areas". Such is life......
Ironically, the Bluestone resort is not in the National Park, and neither is it in an area where bluestone rocks occur -- except as glacial erratics.....
I have been looking again at those red sandstone boulders and cobbles found in the roadworks near Penblewyn, near Narberth. There are quite a lot of them in the glacial deposits -- mostly quite small, less than 50 cm in diameter. They are sub-rounded, but they do have glacial facets on them, and some are clearly striated. HH Thomas (yes, he of the bluestones) recorded other red sandstone boulders in the area, and assumed they had come from the ORS red marl beds -- which are exposed around 3 km to the south of the find site.
This is what I said in another post:
The biggest puzzle relating to the glacial deposits at Penblewyn is the relative abundance of boulders and cobbles of red marls -- coloured bright red and pink. What on earth are they doing here, 3 km to the north of the ORS outcrop? Are they derived from ancient river gravels that have been carried northwards from the outcrop and then incorporated into glacial deposits? That would be vanishingly unlikely, because there is no reason to assume that local drainage ever flowed northwards from the outrop, across the Afon Marlais valley (Lampeter Vale) and up the south-facing slope of the ridge. I checked the old Geological Survey Memoir for the Country around Haverfordwest (1914) and found that similar deposits from nearby are described on page 221: "The presence of red marl from the Old Red Sandstone in this drift.........shows that the transportive agency had a certain amount of northerly direction." The author? None other than our old friend HH Thomas. He was confused, and so am I........At the time nobody knew very much about eustatic and isostatic interactions, but we did know that sea-level had been low during the big glacial episodes, and if there had been a sea-level drop of c 120m at a time of extensive and intensive glaciation, then the coastal platform would have been exposed, and available for ice cap growth. This was the map which we put into the scientific domain:
We postulated in a number of articles that as sea-level fell with the onset of a big glacial episode, more and more of the coastal shelf would have been exposed, leading to a northwards migration of the ice cap axis, in response to high precipitation rates to the north and west of the island ice caps, which must already have been in existence. We thought that there might have been an intervening ice-shelf phase, but we had no way of determining that from the evidence as we saw it.
We suggested that the big glaciation, with ice streams flowing southwards and south-eastwards into the Bransfield Strait via the sounds between the islands, was not the Devensian / Weichselian / Wisconsin glaciation but the preceding one -- or two, or three........
Much ice has flowed and melted since 1966, and although our ideas have stood the test of time there has been a huge amount of research in the South Shetlands and on the Antarctic Peninsula, and it's now apparent that the "offset South Shetlands Ice Cap" which we described has existed on multiple occasions, including -- most recently -- the Weichselian. So the outlet glacier troughs have been occupied by streaming ice over and again, maybe getting deeper with each successive glacial episode. Bethan Davies has written about the most recent deglacial phases around the Bransfield Strait. Some of her maps seem to show an LGM ice cap axis over the island chain, with a grounding line on the shelf, and some show cold-based ice grounded between the South Shetlands and South Orkneys. I must check up on what the latest thinking might be.......
https://www.antarcticglaciers.org/glacial-geology/antarctic-ice-sheet/icesheet_evolution/
https://www.sciencedirect.com/science/article/abs/pii/S027737911100326X
There is now a big literature.
What interests me about all of this is the extent to which we can extrapolate for our studies of "the South Pembrokeshire problem" -- was the area glaciated during the Devensian, or was it not?
If an ice cap could thicken and grow, and if its axis could migrate windwards across a low-lying coastal platform in the South Shetland Islands within the time-frame of a glacial episode, why not in Pembrokeshire too? I shall ponder further.....