I did a post about this back in 2012, but in our discussion we got rather sidetracked by Wilts Museum and copyright issues! I am still interested in this topic, and wonder if anybody knows of any further research / discussions in publications over the past 4 years?
Reference: Field and Pearson report from 2012: Stonehenge, Amesbury, Wilts Archaeological Survey Report (EH Res Dept Report 109-2010.) Downloadable from the web.
The image above is acknowledged as copyright Wiltshire Heritage Museum:
The EH Report is available here: http://research.english-heritage.org.uk/report/?14951
Several things come into the frame here. One is the nature of the majority of the bluestones used in the settings. See this about "The Erratic Bluestone Circle"
The bluestone boulders appear to be abraded and heavily weathered, and many of them appear to be faceted -- just like far-travelled glacial erratics. So if they look like glacial erratics, they just might be glacial erratics, and the place where they were found just might be a degraded moraine.
Another issue is the "honeycomb" nature of the bedrock surface at Stonehenge. This has been remarked upon by many of the Stonehenge archaeologists. It would be stretching things to extremes to claim that the WHOLE bedrock surface is a result of human interference and that it has ALL been affected by work on multiple stone settings. Are at least some of the chalk rock surface pits and hollows natural rather than man-made? Are some of these features solutional hollows and solutional rills? And more to the point, are some of them actually extraction pits from which bluestone and sarsen erratics have been taken -- to then be used in the stone settings?
Interesting topic. I shall explore this further in another post.