Transgressive-regressive cycles, or depositional sequences can serve as fundamental units for taphonomic, paleoecololgical and evolutionary analyses of fossil assemblages. For benthic animals, formation of a depositional sequence means temporal changes of substrate condition, that is, erosion, condensation and rapid deposition. These are critical environmental attributes controlling colonization by benthos. Characteristics of the fossil assemblage are closely related to the stratigraphic and geographic position within the depositional sequence. This means that characteristics and patterns of change in composition of the assemblage, as well as taphonomic processes are predictable from the stratigraphic position within a depositional sequence.
