6.9 Preservation and Burial of Ancient Karst

Abstract

Ancient karst features can be preserved by burial, filling, or by occurring in areas with extremely slow denudation. Although the terms ‘paleokarst', ‘relict karst', ‘buried karst', and ‘fossil karst’ have caused much confusion, paleokarst, buried karst, and relict karst can be defined in terms useful to karst geomorphologists and cave scientists. The term ‘fossil karst’ is best abandoned. Burial and paleokarstification are not necessarily the end of karst. Ancient features may be exhumed and reactivated. Karst ends with denudation at the Earth's surface. Unroofed caves are a particular feature of karst denudation. Most ancient karst features may be preserved by filling, burial, and exhumation. In unusual conditions, karst features have survived at the surface since the Mesozoic. Burial, exhumation, and slow denudation may not be sufficient for extreme survival; relative vertical movement may be required. As caves and many other karst landforms are negative features, they are prone to filling by a range of materials, making cave sediments and paleokarst deposits quite diverse. Whole karst landscapes can be buried and evidence of burial can be recorded in the diagenesis of sediments. Although filled and unfilled caves can survive shallow burial, deep burial can crush caves, forming crackle breccia. Exhumation can occur from the surface following uplift or from below following hypogene speleogenesis. Preservation, burial, and exhumation of ancient karst have two unexpected consequences. Caves can be older than the landscapes in which they occur and stalagmites can be the longest surviving karst features.