Published:January 01, 2006
North American research on surface karst landforms has tended to focus on factors affecting the development and distribution of sinkholes. There have been important quantitative contributions to understanding the formation of solutional, suffosional, and collapse sinks, and a major series of applied geotechnical studies has been published. Gypsum karst, and the impacts of repeated glaciations and permafrost on carbonate, gypsum, and salt karst have received much attention in recent years. North American research dominated the general field of speleogenesis until the past two decades. There are well-understood models for dissolutional cave development in young, newly emerged limestones, for situations where cool or thermal waters ascend from deeper formations, and for descending, unconfined meteoric waters. Worldwide, there is now intensive computer modeling of conduit initiation and enlargement and their relation to the evolution of karst aquifers.
There have been many important advances in the study of cave deposits. Clastic sediments may be dated approximately by paleomagnetics, more precisely by cosmogenic 10Be/26Al decay of quartz sands or pebbles, and by 39Ar/40Ar where clays have been converted to alunite by H2S reactions. Currently, there is a bandwagon in paleoenvironmental studies of speleothems. They can be precisely dated back to 500,000 yr B.P. by U-series methods, their C and O isotope ratios track local and regional environmental changes over the course of the glacial cycles, and many display annual or other significant periodic banding.