Abstract:
Hypogene or per-ascensum, whatever you prefer to call them, caves that form from the bottom up have a great range of patterns in plan, large cavity morphology and an expanding, but specific suite of speleogens that distinguish them from fluvial caves formed by descending surface water. Once thought to be rare and unusual, caves or sections of caves with plans, large cavities and suites of “hypogene” speleogens are turning up in situations traditionally thought to have fluvial or even glacial origin. The role of condensation corrosion in the formation of cavities and speleogens remains controversial, but surprisingly some insights may come for processes in salt mines. Phantom rock formation and removal and similar processes involving removal of dolomitized bedrock, de-dolomitized bedrock, and almost trace-free removal of palaeokarst raise problems of both temporal relationships and of how to distinguish between the outcomes of recent and ancient processes. The presence of “hypogene” speleogens in both gneiss and marble caves in Sri Lankan of unclear origin adds to the complexity. Back in the early 1990s, before hypogene caves were de-rigour, workers such as David Lowe were puzzling about speleo-inception, how caves begin. Perhaps the rare occurrences of solution pockets in joints in obvious fluvial caves, such as Postojna Jama, are indicating that many more caves than we imagine are actually multi-process and multiphase and that “hypogene” processes of various types are significant agents of speleo-inception.