SPELEOGENESIS IN THE QUATERNARY: THE PRESENT IS NOT THE KEY TO THE PAST (Invited Presentation)

Continental glaciations, as have occurred in the Quaternary, are rare in Phanerozoic earth history, prior major events being in the Late Ordovician, Early Devonian, Mississippian/Pennsylvanian boundary, and Permian. The rarity of glaciations is primarily caused by plate tectonics and the resultant infrequent episodic presence of continents at polar latitudes, and secondarily by climatic forcing (e.g. Melankovitch orbital variations). Speleogenesis under the conditions of rapidly changing glacioeustatic sea level, isostatic near and far field effects, atmospheric CO₂ changes, glacial erosion and deposition, and fluctuating temperature and precipitation regimes is very different than the more stable conditions of most of Phanerozoic time. Cave development during earlier global glaciations is almost totally unrepresented in the modern rock record; paleokarst caves therefore reflect genesis at times of relative global climatic stability. While ice contact and proximity effects of ice excavation and deposition, permafrost, and extreme glacial melt water events on speleogenesis are obvious, global effects such as glacioeustasy and local climate changes are often not considered. The shift of the American Southwest from “pluvial” to arid conditions at the Pleistocene to Holocene transition, as also occurred in the Sahara Desert, indicate that even land-locked areas far from the glacial margin did not escape modification of speleogenetic rates and outcomes. Sea-level changes affected all coasts, and as a result of consequent base-level changes, areas deeper into continents. Do the caves we explore and study today reflect mostly fundamental processes common across geologic time, or are they overprinted by glacial and interglacial cycling that obscures those processes? Karst caves in the Quaternary have commonly survived multiple glaciations, and re-established flow paths from the past while simultaneously adjusting to new deranged landscapes. It is suggested that speleogenesis is a robust yet sensitive phenomena that produces karst caves that are a long duration, high fidelity record of earth processes.