Possible that one dissertation in Computational Archaeology could earn two degrees? I'm planning on my PhD to be in CS, but it occurs to me that my research as it applies to archaeology/anthropology will be just as unique and valuable (hopefully) to that field in and of itself.

I haven't been able to find anything on this specifically as in most cases the two fields concerned are closely related and two separate degrees would be unnecessary. In this case, however, it seems fair to ask the question as the two fields are both widely different and at the same time this research in particular would be completely overlapping between the two disciplines. 

If this isn't a thing I'd appreciate any insight on schools which have strong graduate programs in both of these fields; regardless of whether I can earn two degrees (which I'm not expecting) I want to tailor my research and my access to experts/labs/programs as much as possible. 

TIA!
It's hard to say something is definitely not possible, but I think this is a case where it just really isn't worthwhile. A PhD says you can do research; from there, it's more your research output that matters rather than the title of your degree.

What I would strongly suggest, however, is that you pursue having a mixture of faculty on your thesis committee. The exact rules will depend on your program and graduate school policies, but even if there is a requirement that official committee members come from a particular department, at a minimum you should be able to add some "outside" people who can help advise you in your second research area.

You should also pursue publishing papers in both fields.

Of course, all of this will depend on support from your main advisor, so when you look for particular programs, make that part of your search and part of the early conversations you have about your fit.