This is the new pit at Rhosyfelin, out on the valley floor. Having heard that this pit (and the old one, presumably) would be filled in today, I just happened to be passing this morning, and popped in to take some pics before everything disappeared.
This is the "old ground surface" which is being dated as 7,500 years old. It is the upper surface of the clay-rich till and other sediments which underlie the foxy red iron-stained horizon. We don't know how many stones have been taken away by the archaeologists -- but in the middle of this little lot, Prof MPP claims to be able to see a curving "routeway" along which bluestone orthostats from his beloved quarry were trundled on their way down the valley (northwards) and thence towards Stonehenge. If you can see a trackway here, you are a better person than I.
According to the gospel story, this trackway is connected to a "loading platform" and a quayside and revetment, just to the left off the edge of the photo. This is what the latter features look like in reality: