Several of these crevices intersect the tunnel as it leaves the famers field. This is the last such feature before the waterflow (of which there was very little this day) disappears entirely into a mound of debris. As for its reappearance, we were unable to be entirely sure as to where that would be but it would definitly be some significant distance away.
This is a spot that D suggested I probe around as from the surface it was in his opinion, “Very similar in appearance to the pheratic tunnel entrance at XS Wired cave”. It was sort of a toilet seat shape that demarcates the transition between a surface joint and a pheratic tube.
Cave tunnels form either above or beneath the water table. Those that form above the water table are generally deep and trench like as the water within moves under the influence of gravity and all wear is along the base of the channel. Beneath the water table the tunnels are usually elliptical or circular tubes as the erosive processes are concentrated more evenly all around on the tunnel walls.