Hi Rich, welcome to the forums!
It's really great to see people pop up in forums with a different expertise.
Because frankly, as you have pointed out already more or less, we're mostly just fiddling a bit here with terrains.
Accurate modeling is something you seldomly see here.
I think.
For now I don't have a specific project running which could use your help, but I'm very curious to hear your ideas.
What's your area of expertise within geology?
Do you have experience with coding (geology) models or anything else related to Geology & 3D/Computer Science?
Mick (mhaze) his idea of giving Terragen a go to see what's involved in modeling a terrain is perhaps a good one.
It will at least show you a bit of the difficulties and as experience grows can also learn you what's possible (or not).
You mentioned you're mostly bothered by the geology/texturing in games.
Yet, you ended up here
How did that happen?
Cheers,
Martin