This is in important and interesting layer in the mantle, which qualifies a page of its own. It needs more editing, but I put it out there so others can contribute.

This page is obviously a stub, but it's an important region of the Earth (eg a google scholar search giver ~30000 results for lowermost mantle, and that's without talking about the D$'$' or the mineral physics phase change. PKIKPPKIKP ( talk) 18:38, 22 July 2016 (UTC) reply