Andy, what shows up at surface is interesting, but it will take the drilling to determine what is down below. It will take drilling over an area and along a length to be able to create a picture of how the surface features develop at different lower levels. Drilling costs money, so it would make sense to me to do the shallow drilling first in order to extend the 3D model/map further. Once that data is tabulated and digested, it should then also help to shape the next round of drilling at lower levels, thereby reducing the cost and improving the probability of achieving better results when exploring further down.

JMHO.

NL