| Abstract: | Multiple levels evolved in Buddha–Christian's Cave and in Donaldson's–Bronson's–Twin Cave in a subtly different manner to that normally associated with the development of multilevel caves adjacent to entrenched river valleys. It is often assumed that lower cave levels are generated by successive phases of valley entrenchment; however, multiple levels may also be induced by progressive adjustments in groundwater flow paths. Such adjustments occur as the effects of a change in base level propagate up-basin. In the Mitchell Plain much of the late Pleistocene drop in the elevation of the principal drainage (the East Fork of the White River) was accommodated by entrenchment along the lower reaches of tributary valleys. Caves initially developed in the mid-sections of tributary basins at relatively shallow depths. In the vicinity of the cave exit, the piezometric surface gradually steepened and was eventually lowered through a combination of valley headwall retreat and the incremental concentration of flow through master conduits. Upper-level passages were abandoned once the original high-level flow paths were replaced by lower-level routes. |
