Not coreopsis.
Possibly Chrysopsis or Heterotheca.
Maybe this one:
http://www.southeasternflora.c...
Here's a pic (of the leaves) from that link...
http://www.southeasternflora.c...
But I'm not sure about the id...
right plant... may not be the correct name.
Such a common autumn bloomer (in the dry sand), and so difficult to ID.