Microstructure of Billings Shale and Biochemical Alteration Products, Ottawa, Canada

Abstract

A microstructural analysis has been made of altered and unaltered black shale from a site where foundation heave has occurred. Jarosite framboids composed of very small interlocking crystals, much larger crystals of gypsum and microorganisms are described in the altered shale. The relative roles of jarosite, gypsum, and other hydrated sulphates in the generation of heave forces is not fully understood. If jarosite is responsible, most black shales have a heave potential; if gypsum is responsible only black shales which contain carbonate need be of concern. Recognition of fungi and other microbes suggests a more complex biogeochemical cycle than previously supposed; the use of microorganisms as a method of controlling heave warrants more investigation.