Perspectives on the Sequence Stratigraphy of Continental Strata

Abstract

This report is the result of a working group on continental sequence stratigraphy that was set up at the 1991 NUNA conference in Banff, Canada. To date, sequence stratigraphic concepts have been applied mainly to the marine realm, but unconformity-bounded units have long been recognized in nonmarine strata. Successful application of sequence stratigraphic concepts to continental strata requires careful consideration of controls on base level and sediment supply. As with shallow marine environments, relative sea level can be considered as the stratigraphic as well as the geomorphic base level for coastal nonmarine settings. Farther inland, stratigraphic base level, which determines accommodation space, is more complex and takes various forms, such as the graded profile for fluvial strata, groundwater tables for some eolian strata, and lake level for some intermontane sediments. Sediment supply is also generally a more complex variable for nonmarine environments than in the marine realm because of the proximity to the source area. The influence of climate and tectonism on sediment supply can clearly be seen in many continental sediments. The fact that the major controls of climate, tectonism, and eustasy are somewhat interdependent, and that a change in one parameter will most likely be reflected in others, is also more readily apparent in continental strata. Although in its infancy, sequence stratigraphic concepts have been applied to a wide variety of continental settings in attempts to explain variations in facies architecture. Of particular interest are studies that have linked fluvial architecture on coastal plains to variations in relative sea level as indicated by coeval marine strata, and studies of lacustrine environments that show marked variation in facies between highstand and lowstand deposits. The application of sequence stratigraphy to continental strata will likely result in the development of better correlation techniques and models that better predict the location and nature of fluvial and eolian reservoirs.