The gully between the hills - Marble Hill Stow, MA

This is a map fragment of Marble Hill in Stow, MA. There are numerous sites on this and adjacent hills, and between them. Look at the gully separating Marble Hill from the next hill to the northwest. I would expect to see a little something in there and, in fact, there where three rock-on-rocks right at the point where the water comes out of the ground and flows off to the southwest.
Noticing the shape of the upper rock, I wonder if this is another example of a "comma"?

It is not too risky to drink water that is coming out of the ground and I did. It was delicious.