Stone Married Up (Pearson et al, 2019)

M.P. Pearson & UCL have released a new study in Antiquity,"Megalith quarries for Stonehenge's Bluestones", and it confirms and pinpoints half of Stonehenge's bluestones to a time and specific place in a Welsh quarry known as Carn Goedog. 

The bluestones form the smaller Q and R circle & horseshoe of spotted dolerite within the outer sarsens trilithons (see diagram below), but still weigh up to two tons.  Since Carn Goedog is on the northside of Wales, Pearson and colleagues think they made much of the 150 mile journey over land.
 

Pearson and bluies (Adam Sandford via CNN)

One thing can now be conclusively crossed off the list.  Glaciers dumping these boulders off in the Salisbury plain - nope.  At least for the bluestones, these were collected and transported by people.  The researchers have found the ancient tools to quarry the stones and the exposed rock invite the possibility that this is the exact location where the stones will marry up. 

Based on the dates taken at Carn Goedog, the stones were quarried around 3,000 with considerable confidence and very closely corresponds to the Aubrey holes of Stonehenge.  The Aubrey holes are thought to be the original position of the bluestones before the entire monument was re-arranged for a new religion (probably by the Bell Beakers).

At the quarry, it appears that the remaining stones were 'protected'.  That means whoever controlled the quarry piled a bunch of crap around and below the native 'bluestones' to prevent any more from being quarried -weird!

The ancient quarry Carn Goedog (Adam Sandford via CNN)

Finally, it's possible that this half of the Stonehenge bluestones (and probably the other half as well), were originally part of another monument, if only a short while.  It might be a situation similar to Medieval relict-plundering - the stealing of religious items for another holy place.

That probably would have happened before the Beakers, however it was likely Beakers that moved the bluestones to their tighter position before finishing the monument in its current form.