Review: The RASC and CASC programs for ranking, scaling and correlation of biostratigraphic events

RASC is an acronym for RAnking and SCcaling of biostratigraphic events. Code of the RASC computer program was originally published in Computers & Geosciences. During the past 30 years this program has been continuously maintained and updated. Its purpose is to combine biostratigraphic data from land-based sections or exploratory wells drilled in sedimentary basins to construct a regional biozonation that can be used for correlation between sections within a study area. Different methods of quantitative stratigraphy are briefly reviewed in this paper. Ranking is illustrated by application to a simple, artificial dataset. Scaling is explained as a refinement of ranking. Implications of sampling of stratigraphic sections are discussed in detail. Several examples of past successful large-scale RASC applications are given. These include results for well data from the Cenozoic North Sea basin, northwestern Atlantic margin and the Cretaceous seaway between Norway and Greenland. Paleoceanographic interpretations of RASC biozonations supplemented by analysis of variance and correlations between wells are exemplified as well. History of program development is summarized in an Appendix.