Erratics resting on glacially polished and striated granitic bedrock along Murphy Creek, north of Tenaya Lake in Yosemite National Park, USA...........
I have been throwing out old geology and geomorphology text books, and in the process found this photo. It reminds us that if the Stonehenge bluestones were indeed scattered across the landscape of the downs, you do not necessarily expect to find large terminal moraines or indeed coherent glacial deposits in the immediate vicinity.........
3 comments:
Please excuse my ignorance with this question but I cannot find an answer anywhere. If the bluestone erratics were transported in an early glaciation, would they have been deposited onto the present land surface or onto the surface of a long gone silcrete carapace?
I doubt that the erratics are that old. But they might have come from an early glacial episode more than a million years ago. There may or may not have been glacial deposits associated with them -- largely now destroyed by solifluction and other processes. But the chalk surface might have lowered as a result of solutional processes; the famous "periglaciial stripes" are probably not periglacial at all -- they seem to me to be solutional rills.......
But am I right in thinking that Salisbury Plain was covered by a Silcrete carapace i.e Sarsen stone and if so for how long and could solutional rills have formed underneath it?
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