Scientists discover source of rock used in Stonehenge's first circle - News - Archaeology - The Independent:
The work - carried out by geologists Robert Ixer of the University of Leicester and Richard Bevins of the National Museum of Wales - has pinpointed the source as a 70 metre long rock outcrop called Craig Rhos-y-Felin, near Pont Saeson in north Pembrokeshire. It's the first time that an exact source has been found for any of the stones thought to have been used to build Stonehenge.
The discovery has re-invigorated one of academia's longest running debates - whether the smaller standing stones of Stonehenge were quarried and brought all the way there from Pembrokeshire by prehistoric humans or whether they had already been plucked out of ancient rock outcrops and carried all or part of the way to Wiltshire by glaciers hundreds of thousands of years earlier.
Archaeologists tend to subscribe to the 'human transport' theory, while some geomorphologists favour the glacial one. The debate is solely about Stonehenge's early/smaller standing stones (often known collectively as 'bluestones') - not about the larger ones (most of the so-called 'sarsens') which were incorporated into the monument several centuries later.