Yes, I tested all my header lines and found that was the 'offender." It got there on someone's suggestion it was needed for proper TikZ. Or was it bibtex? Or does a ton of pngs come if you choose Latex preview? No time for further investigation. Confusion will be my epitaph. . . .

On Tue, Jan 10, 2017 at 3:21 AM, Eric S Fraga <e.fraga@ucl.ac.uk> wrote:
On Tuesday, 10 Jan 2017 at 00:13, Lawrence Bottorff wrote:
> This is the entirety of my header section. I'm sure there are
> redundancies etc. But again, the clean vanilla of Emacs 25.1.1 and
> org-mode 9.0.2 is defaulting to producing png's.

[...]

> #+OPTIONS: tex:imagemagick

Maybe this is the problem?

--
: Eric S Fraga (0xFFFCF67D), Emacs 26.0.50.1, Org release_9.0.3-189-ge46676