Interesting question.
I don't have a direct answer but I can share my opinion. Ansel died April 22, 1984 around mid to late afternoon. I seem to remember 3:15 but I may be mistaken about the time. The date I remember very well for it is the same date and time that my father also passed away. I had the opportunity to attend an Ansel workshop and I found him to be an interesting person. I had respect for him because he believed in what he stood for, he had convection. I may not have agreed with him on all points but I respected him. My father was the same way. Strong convection in what he believed and at times my father and I were at odds.
As to where Ansel is buried, I attended a John Sexton workshop that October and this very question came up. John's answer, "He's in the Final Wash"!
Take that how ever you want, but my suspicion is he was cremated and his ashes were spread over Yosemite.
Makes for a "Happy Ending"
Gary