Physical pole shift would explain some of the same actions. Actually, something passing close enough to the earth might have triggered a pole shift.
THAT is not something you really want to have happen again. At least not while anyone you love is still alive.
That would give us a date for the burial of the site ~ and, koinkydinkily, an event that could be timed perfectly with the use of Sumerian astronomical observations. Following the catastrophe (about 8,000 years back) folks would have lost memory of the use of the funeral/memorial site.