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Thursday, 25 August 2011

The Monsters from Daylight Rock (2)

 Possible post-glacial coastline positions around Caldey  -- as at the dates indicated.  Click to enlarge.

Given that Ice Age creatures were inhabiting caves on Caldey and on the adjacent hillsides near Tenby between 30,000 and 18,000 years ago, when sea level was far below its present position and when the whole district was dry land, we need to ask where the ice edge might have been at the time.  Cave lions, woolly rhinoceros, cave hyaena, cave bear, horse, woolly mammoth, hippopotamus, brown bear, giant Irish deer, bison, wolf and reindeer were all tundra animals, living in a landscape of cold-tolerant plants including dwarf birch and dwarf willow, grasses, mosses, bilberry etc -- very much like the tundra of today, as we see it in East Greenland and the Arctic fringes.  There might have been some areas of scrub birch and even conifers, but with the ground surface underlain by permafrost most of the countryside would have been open, with great expanses of bogs and standing water and with perennial snowpatches surviving throughout the year in shady locations.

As the Devensian cooling occurred snowpatches would have coalesced, lakes and open water areas would have contracted, and copses of trees might well have died as summers shortened and winters lengthened.  The animals might well have hung on, just as bears, wolves, reindeer and musk-oxen survive very close to the edges of active glaciers today.  Were they hunted by human inhabitants?  Very probably, since the dates of the Eel Point and Paviland human remains place them solidly into this period of Ice Age habitation.

So where was the ice edge at the time of the Devensian maximum?  Until yesterday, I thought it was located somewhere out to the west, near the mouth of Milford Haven.  Now I'm not so sure, following my discovery of Devensian till right at the eastern tip of Caldey Island........


Constantinos Ragazas said...

Brian you write,

“As the Devensian cooling occurred ... lakes and open water areas would have contracted...”

Is that an odd way of saying that during the Devensian lakes, rivers and other waterways would have frozen solid? This is what I have been saying all along!

I think we may be narrowing our differences down to how big these bodies of water were at the time of the Devensian. I think they were vast while you think they were slight.

I think they were vast because these formed during the Great Melt which immediately preceded the Big Freeze. Why do you think they were slight?

And of course, following the Big Freeze we once again have a sharp rise in global temperatures with consequent melting of the ice once again.

All this I take from the charts of average global temperatures you have posted in the past!

Now consider that the ice sheets so formed where over a landscape with geothermal subterranean hot spots! This is a reasonable hypothesis supported by the following facts:

1)The geological history of Wales with many very active volcanoes in the past.

2)The existence of geothermal hot spots in places like The Bath (the hottest waters in all of Europe!)

3)The surprising and unexpected high temperatures of boreholes around Stonehenge in recent excavations.

The combination of local ice sheets over an active geothermal terrain created an ice-scape of various 'ice holes' (circular, oval etc.) that resulted in the landscape we see today. The stone-circles were formed collaboratively by Nature and Man.

I will go out on a limp and propose the following: The geothermal temperatures where prehistoric monuments exist (stone circles, henges, round mounts, etc.) are generally higher than in other parts of the area!

Can you get your geologist colleagues to 'falsify' my hypothesis through scientific field study?


BRIAN JOHN said...

Nobody is going to bother falsifying any of this, Kostas, unless you come up with some evidence instead of just a hypothesis. None of your "evidence" has anything to do with the area which I am considering here, and your geothermal hot spots, great melts and sheets of water, and link with volcanic activity is all sheer speculation.

Alex Gee said...

Hi Brian
When do you suppose the channel between Caldy Island and the Mainland was eroded? fairly recently as a cosequence of wave action? I think you're definitely onto something. Think of the cave bears occupying Kent's Cavern, was the Torbay area in South Devon near the ice edge?

BRIAN JOHN said...

I think the "channel" between Caldey and the mainland is very old -- under water whenever sea-level is high, and dry land when sea level is low. There are traces of the raised beach platform on the north side of the island -- that means higher sea-levels in the past, with Caldey cut off from the mainland.

Kent's Cavern -- not sure that the presence of animal bones in caves tells us anything much, except that the caves were open or accessible at a time of cold climate when there was extensive tundra all around....