No, MTS is about the same density as the sand. Fine particles migrate to the bottom and large ones migrate upwards. I think that holds true even if the fines are less dense, as long as they don't float. It happens because fines sink into tiny openings, then slight movement of the larger particles opens some more fine openings, until finally all of the fines end up at the bottom. It even happens in ordinary dirt in a farm field. You can remove all of the rocks from such a field, and a year later another batch has worked its way up to the surface.