Nearly two decades ago, Marshall Kay (in Grabau, 1960) wrote an interesting prefatory note to the paperback version of Grabau’s (1913) remarkable compendium concerning the

lithogenesis of sedimentary rocks - Principles of Stratigraphy. Kay indicated that since Grabeau’s book was written, much had been learned because of the increased depths and numbers of wells drilled by the petroleum industry. “The knowledge gained from rock cores, the analysis of sediments and microfossils, and the varied geophysical probes [well logs] in such borings, as well as those relating to greater depths, have vastly increased our understanding of sedimentary rocks in three dimensions”, stated Kay. And since Kay’s statement, many thousands of wells have been drilled, cored, sampled and logged with wireline well logs.

The sedimentological and geochemial techniques and principles thus far described in these short course notes are most appropriate to the direct examination of rock. Clearly, subsurface studies should utilize drill cores for chemical, paleontological, and detailed sedimentological analyses. However, the vulnerability of evaporite deposits to dissolution, deformation, and complex diagenesis necessitates the use of all subsurface data available.

Well logs and samples of cuttings provide the two most abundant records of subsurface geology. Unfortunately, since the introduction of well logs there has been a somewhat decreased concern regarding the sampling of well cuttings that has lessened the contribution of this important resource of subsurface data. Well cuttings and many well logs have sampling problems such as the influence of poor borehole conditions (Misk and others, 1977) and lack of