Mark:
The feature does not have a name, as far as I'm aware.
You used to see this some on turn-of-the-century courses. National Golf Links #17 had a big sand mound in front of the green ... there is more grass on it now. Generally, a pure sand mound does not hold up well to winds etc, so these features go away over time. The mound at Garden City is actually built mostly out of fill dirt and gravel, with only a bit of sand over the top of it, so it will hold its form over time.