What does the position of the west bastion of the actual site of the jamestown indicate?

The western most part of the palisade was destroyed by the construction of the Pocahontas monument in the early 1920's. The palisade also seems to have been impacted by some sort of earth moving on the southern section closest to the modern seawall.

Around the early 1920s the construction of a monument of Pocahantas led to the tearing down of the westmost bastion. Most of Jamestown is intact, though, or replaced with a replica.

Answer glacier terminus;

The answer is d., a mountain.