ABSTRACT
The cave possibly originated beneath the Stephen impermeable cover rocks as a single phreatic loop of >370 m depth (Ford et al., 2000). More certainly, as Castleguard Valley was entrenched below the Stephen Formation, the cave became enlarged to its modern dimensions as shown in Figure 3b, two shallow, principal loops consisting of vadose entrenchments up to 15 m deep draining into phreatic tubes of beautiful circularity (Figure 4). Following this main phase, the cave drained through undercapture passages in the bottoms of the loops (Figure 3c). The undercaptures channel local invasion waters today and the Downstream Complex can be flooded from another lifting shaft, Boon’s Blunder, and discharged through the explorers’ entrance, closing it.
