I was reading some stuff about Henges a while back, and the author (Burl or Darvill, can't remember which) thought that during the bronze age, the whole age of ancester worship was starting to be superceded by the cult of the stone circle. Could this stone burial represent the symbolic, 'putting to sleep' of an older cultural tradition. Dunno, just a thought. Or did it happen in more recent times. You know how those crazy christians love to bury/destroy the remains of prior cultures, and especially stone(s)/ circles.