There must be a simple explanation...
My best uneducated guess: A massive ring of debris containing many micro-sized and pebble sized particals that collapsed into a flat ring about the world's equator where they eventually rained down on the surface, solidifying into a single global encirling geologic feature. It would have had to have happened over a fairly long period of time, but still have been fairly recently in geologic times (like the last 50 million years or so)?
Now: Why don't we see similiar features on other bodies in the Solar system?
Anybody else have an explanation?
Scott Evil