Don't know any references to cemeteries and landforms. There is the big book
of Vermont cemeteries published by the Vermont Old Cemetery Association,
which may have some information of this sort, although i don't remember
seeing it (possibly because I never looked for it).
There are two issues of the Dublin Seminar for New England Folklife on
Puritan gravestone art (vol. 1, 1976; vol. 3, 1978). Maybe there is an essay
in there on your topic.