It’s a nightmare to think that the fairly small unique outcrop of stones was moved by glaciers basically due east to the Salisbury plain, and that not a single one was lost along the way by the ice. But regardless, that was an excellent restatement!
perhaps (offhand guess) the geologists envision a large mass of bluestone broken up at the source and distributed widely over a very large area, including the Salisbury Plain. However, then the next logical question might be where are all the other large bluestone liths that should in theory still be lying around. in any case not having the full article is difficult.
Ahh, but absence of evidence isn’t necessarily evidence of absence.
The fact that Salisbury Plain is mostly clear of stones now doesn’t mean it was that way in the past. Remember, Wiltshire and Somerset is some of the most intensively farmed and occupied real estate on the planet and has been for thousands of years and farmers spend a lot of time and effort removing obstacles like big rocks from their land.
There are a few small parts of the area that have apparently never been farmed or developed and offer a glimpse of the Mesolithic/Neolithic environment. One of them is called Lockeridge Dene and it’s now protected by law.
Here’s a photo of one of the main meadows and, as you can see, it’s covered with glacially moved rocks.
http://www.fotolibra.com/gallery/1180386/sarsen-stones-lockeridge-dene-wiltshire/
I was lucky enough to visit it after a trip to Stonehenge and it’s a magical place. In fact, I’d recommend to anyone planning to visit Stonehenge, do some reading and take the time to view the place in context - an amazing amount is still preserved. Visit Dunnington Walls and walk the river Avon and the ceremonial entranceway to the stones themselves (about a 3m walk, in all). The approach that way is as they were planned to be seen by the people that constructed them and is mind blowing. So much better than the depressing car park, visitor center and highway that you have to cross.