I think it is highly unlikely that any historians, anthropologists or archaeologists will answer this question because to do so would be unethical. Information about Native American sites of religious importance is almost always private, and not a matter of public discussion. There is a rich history of desecration of sites of religious importance to Native Americans. Very sensitive sites have been plundered by collectors, defaced by vandals and destroyed by developmers. Natives can get more than little pissed off about this and they have every right to.

It really does not matter what the motivation behind your question is, the answer will likely be the same. If you want more information about this, I recommend you contact any tribal official of any tribe in America. They will likely provide an enthusiastic response. For an interesting look at Native efforts at protecting cemeteries (they are of high religious importance to Native Californians), see Tony Platt's book "Grave matters:Excavating Californias Buried Past".

I’m sure if you contacted tribes in PA they’d help point you in the right direction