Rune matey
I ain't really suggesting that the monuments of the wolds were exposed chalk, although it isn't an impossibility but I guess there's no evidence for it. What I was clumsily trying to point out was the connection between Wessex and E. Yorks...two contemporary and very materialy rich cultures who influenced each other e.g. the great wolds mounds such as Duggleby Howe have been speculated as being proto-silburys.
As for the greening of the chalk, I guess there is plenty of archaeological evidence for the periodic re-cutting of henge ditches.
Really what I was getting at, when bringing in E. Yorks, was the significance of chalk landscapes to the early farmers, same rules apply to limestone and gravel terraces.. well drained, lovely soils with a good local supply of the stuff that makes decent farm implements...there is often little emphasis made on the importance of a plentiful supply of good quality tools, without good blades a farmer is fucked. Hence the abundance of finds in these areas.