Glacial Karst Aspects About the DeKalb Mounds in Illinois, USA

ABSTRACT

The glacial dead-ice origin of the DeKalb mounds in DeKalb County, Illinois, USA, is advanced in this study by discussing it within the context of late Wisconsinan glacial karst. Glacial karst is glacial dead-ice topography that resembles carbonate bedrock karst topography. The only difference here is that thermo-erosion or melting of ice by groundwater causes glacial karst, while dissolution of carbonates by groundwater causes bedrock karst. For example, bedrock karst such as haystack hills, dolines and entranceless caves analogously match up to stagnant glacial ice blocks with supraglacial ice pits and entranceless glacial caves. Entranceless bedrock caves are caves with no opening (entranceway) that is big enough for a human, yet contain water and/or accumulations of silt and clay. Although stagnant glacial ice blocks and supraglacial ice pits have been discussed in the literature, entranceless glacial caves is an undeveloped concept which is expounded in this study. An entranceless glacial cave is actually a subglacial/englacial, water-filled cavity formed by thermo-erosion due to active-layer groundwater/talik piping laterally seeping out of the adjoining terrain and into a body of glacial ice, as seen in modern glaciers of Antarctica. This type of water-filled cavity can also be classified as a subglacial or englacial lake. The study also discusses relationships to embryonic DeKalb mounds such as: why a localized part of the continental ice sheet degenerated into stagnant ice blocks; and the Wisconsinan creation of one or more steep depressions in the till plain underlying a DeKalb mound.

Keywords:

DeKalb mounds , entranceless glacial caves, glacial dead ice, glacial karst, ice pits, stagnant glacial ice blocks.