Interpretation of Biostratigraphic Data at a Sequence Stratigraphic Scale

Abstract

Recent advances in sequence stratigraphic concepts provide a framework within which biostratigraphic data can be used in conjunction with other stratigraphic tools in an integrated approach to stratigraphic analysis. Sequence stratigraphic concepts suggest that lithologic sections are composed of a succession of unconformity-bounded units or sequences. These sequences can, in turn, be subdivided into systems tracts bounded by flooding surfaces or maximum flooding surfaces. Three systems tracts comprise a sequence: the lowstand or shelf margin systems tract at the base, followed by the transgressive systems tract, and the highstand systems tract. On continental margins with a discrete shelf/slope break, deep-sea submarine fans, shelf-margin deltas, and incised-valley fills characterize the lowstand systems tract. On ramp-like continental margin, the lowstand systems tract is characterized by basinally-isolated lowstand shorelines with or without preserved incised-valley feeder systems. The transgressive systems tract has backstepping shorelines and estuarine fill of incised valley systems. The highstand systems tract is has forestepping depositional systems and widespread floodplain development. A large amount of the structure in the stratigraphic distribution of fossils can be attributed to sequence architecture. This structure can be statistically delineated in terms of a hierarchy that is independent of both fossil group and geological age. Themore » definition of [open quotes]biological analogs[close quotes] of systems tracts reduces the complexity of paleontological census data to a set of (1) internal characteristics within genetic units and (2) boundary conditions at stratal discontinuities. Different taxon groups should display unique and repeatable patterns within different systems tracts and at stratal discontinuities within a basin, providing a new perspective of paleontological data across a spectrum of applications in sequence characterization and correlation.« less