What I was looking for in most of these was depth of field, thus the high
ISO and small aperture.
And, I was wanting to see what effect the higher ISO had on the pictures,
but I didn't want to take
it all the way to the max of 1600.


Your thinking is correct in that the higher ISO will afford a smaller
aperture and therefore a greater depth of field. A deep depth of field is
important in landscapes such as these only when you have a subject in the
very near foreground that you want to be in focus along with the
intermediate and background subjects. In most of these photos, there isn't a
close foreground subject, so a deep depth of field isn't really required.
In the photos where the grasses are in the foreground, perhaps a bit more
depth of field is required, but not all that much. The penalty of an
unnecessarily small aperture is lens diffraction, which can reduce
sharpness.

Since I shoot primarily landscapes, I'm very much attuned to the issue of
depth of field. In fact, it is because of this that I almost always shoot
in aperture priority mode. I let the depth of field requirements of the
scene dictate the aperture setting I use and will let the shutter speed and
ISO remain variable. My default aperture is f8, because it usually offers
enough depth of field and is typically the sweet spot of sharpness in most
lenses. If I require more depth of field I will either stop the lens down
further or use a wider focal length. If I am trying to narrow the depth of
field, I'll do the opposite. In any case, I'll typically set the focus at a
hyperfocal distance (somewhere between the foreground and background of the
scene. Also, I always shoot a scene with several bracketed exposures, often
using different aperture settings and then sort it all out at home using a
large monitor.

Perhaps on your next trip out west we can hook up for a photo shoot.

Russ