208 ILLINOIS STATE ACADEMY OF SCIENCE 



PALEOZOIC KARST TOPOGRAPHY 



George E. Erblaw, State Geological Survey 



Karst topography is that unique physiographic ex- 

 pression which- is characterized by surficial sinks, "lost" 

 rivers, natural tunnels or bridges, subsurface solution 

 channels, and subterranean caverns. The name ' ' Karst ' ' 

 was applied because of the remarkable development of 

 this type of topography in the Karst or Carso plateau 

 of Austria. 1 • 



Since it results from solution, karst topography can 

 occur only in areas that are closely underlain by thick 

 beds of limestone, dolomite, gypsum, salt, or other sol- 

 uble rock formations. Most of the known areas of karst 

 topography are underlain by limestone or dolomite. 

 Many karst areas occur in the United States and other 

 countries. 



In many localities, such as northwestern Illinois and 

 southwestern Missouri, valuable mineral deposits have 

 been described as filling ancient solution channels and 

 cavities. This is indirect proof that karst topography 

 existed in geologic periods other than the present. 

 Unique and direct evidence of this fact was obtained last 

 summer in the vicinity of Kankakee, Illinois, which area 

 is underlain by Niagaran limestone or dolomite at a very 

 shallow depth. 



In the quarry of the Lehigh Stone Company, seven 

 miles west and one mile south of Kankakee, are "clay 

 pockets" which on examination proved to be deposits of 

 shale in cavities that are clearly fossil sinks. All of the 

 cavities have the shape of a funnel or a cone with the 

 apex downward. In some of them the walls have a 

 gentle average slope; in others they are precipitate. 

 Again, regardless of the degree of their slope, the walls 

 have a constant and consistent pitch from top to bottom, 

 or they may be made up of alternating projecting and 

 receding layers when the slope is precipitate or of 

 alternating pitches and flats when the average slope 

 is gentle. Except where the wall has collapsed 

 before or during deposition of the shale, it has gen- 



1 Sanders, E. M., "The Cycle of Erosion, in a Karst Region (After 

 Cvijic)'*, Geog. Review, v. 11, No. 4, p. 593-604, 1921. 



