When I look through a lot of Bullock's work it always reminds me of Minor White and some work of Paul Caponigro. There is often a mystical, multi-layering to his images.
Bullock was not just interested in the literal represnetation of things even though he was considered part of the "California School" of photo realism. He used the LF camera and techniques of an Adams or Weston but sought a deeper meaning. In a compilation I have of Mid 20th century photographers the author talks of Bullock writing about the "need to find new symbols...that expand our minds so that we may be more home in this scientific and terrifying age."