Carbonate rocks are a dominant lithology throughout Indiana, and they occur in rock units from upper Cambrian to upper Pennsylvanian in age. Because they are a primary source of energy and mineral resources in the state, they are examined extensively in cores and quarry faces. The description of any rock can, however, vary, depending on the technical skills and background of the examiner and the intended purpose for describing the rock. Carbonates are also complex and highly variable in their grain types and textures. The result is that the same rock could be described in different ways in the field or laboratory depending on the experience and needs of the person describing it. The fact that there are several formal and informal classification schemes used to describe carbonate rocks further complicates this communication problem. Some of these schemes were designed to be used in the field, while others are more suited to examination by petrographic microscope in the laboratory.
For these reasons, we created this corebook in the hopes of standardizing terminology; using it, you can make a relatively quick, yet systematic, description of the carbonate rocks typically found in Indiana. This approach and terminology can be applied in varying degrees of detail, but it will still provide a fast, accurate, and consistent method of describing hand samples of carbonate rock by persons having diverse technical backgrounds, including geologists, engineers, drillers, miners, regulators, archivists, and educators.
