The Terra Rossa Limestone Contact Phenomena in Karst, Southern Indiana

Abstract

AbstractA prevalent view is that the red clayey parent material (terra rossa) of Crider and associated soils is a residual product from solution of limestone in the karst of southern Indiana. The sharp, abrupt contact between terra rossa and limestone provides no evidence to support the concept of a residual origin from limestone solution. In addition, insufficient quantities of insoluble residue in the rock require dissolution of thickness greater than the limestone available. Elemental oxides common in the clay are many magnitudes greater than in the rock and vice versa. Clay minerals in the red clay differ in kind and amount from those of the rock. The <2µm size fraction is many magnitudes greater in the red clay than in the rock. Soil‐geomorphic studies indicate that the terra rossa is mainly debris derived from erosion of higher lying clastic sedmentary rocks and transport and deposition of that debris (pedisediment) on pediments cut into lower lying limestones. The pedisediment subsequently weathers to terra rossa. Therefore the premise is rejected that terra rossa is a residual product from the solution of limestone.