ABSTRACT

Sedimentary geology is rooted in the origin of stratigraphy around 1800. In spite of scattered early flashes of genius, sedimentology did not gain identity until about 1930. Heavy-mineral petrography and grain-size analysis came into their own in the 1920s and the promise of these plus micropaleontology for application in the petroleum industry stimulated the creation of the Society of Economic Paleontologists and Mineralogists (SEPM) in 1926. The Journal of Sedimentary Petrology and several treatises on sedimentary petrography appeared before World War II. After the war, lithostratigraphy emerged apter 150 years of index-fossil dominance.

Studies of modern environments were slow to develop until after World War II, when deltas, barriers, reefs, and carbonate banks were examined. These and similar later investigations have added enormous catalogues of information about both marine and non marine systems, but it is often difficult to integrate the results with ancient sediments. Through stimulus by engineering experiments in fluvial transport and experimental turbidity currents, the rigorous study of sedimentary processes also began in the 1950s. Soon vertical-sequence analysis and formulation of facies models commenced. Today we are experiencing a "model mania," but there is little agreement on what a sedimentary model really should be.

Whither next? Mudrocks will arrive at last and sophisticated instruments promise continuing advances in studies of grains, chemical sedimentation, diagenesis, etc. Even more exciting, however, is that the wedding of sequence stratigraphy, which evolved from lithostratigraphy, and event stratigraphy, which evolved from process and facies-sequence studies, promises an overdue synthesis of sedimentary geology. At last it should be possible to construct true quantitative and predictive models that can evaluate stochastic and deterministic as well as episodic and periodic phenomena at all scales from local events to global eustasy.