PSEUDOKARST DEVELOPMENT IN GLACIATED TERRAINS

The effects of glaciation on karst caves are well known; glaciation removes, modifies, and enhances karst. Glacial effects with respect to pseudokarst development are less well studied, but are similar. Glacial loading creates isostatic depression, with erosion and subsequent unloading resulting in rebound, activating and enlarging pre-existing faults, joints, and fractures. Glacial erosion creates numerous scarps with slopes at angles unsupportive of the rock mass, causing additional gapping of fractures and the formation of fracture caves when roofed over. In massive lithologies complete failure of such slopes results in talus fields with enterable interstices. These fields can contain kilometer-long talus caves in rock types such as conglomerates, massively bedded sandstone, schist, gneiss, and granite. Fracture and talus caves are transient over multiple glacial cycles, as their surficial expression leaves them vulnerable to removal by subsequent glacial advance. Sea, or littoral caves are created along ocean coasts, and inland along glacial lakes where gapped fractures are enlarged by wave action. Littoral caves are prone to preservation through glacial cycles as rapid uplift upon deglaciation positions these caves above sea level, leaving them more numerous than in areas with larger time scales of sea level change. As time proceeds after deglaciation, these cave-development mechanisms decrease in effectiveness, as isostatic rebound wanes, slopes achieve stability, relative sea level becomes stable, and glacial lakes become sediment filled. The Late Quaternary, with its high amplitude, closely spaced glaciation-deglaciation cycles, may be one of the most productive pseudokarst environments in global history.