A model for high resolution sequence stratigraphy within extensional basins

Existing sequence stratigraphic models imply that for any given time period in a sedimentary basin, the interplay between rates of eustatic sea-level change and subsidence will dictate the type of sequence boundary formed (type-1 boundary if rate of sea-level fall exceeds subsidence and type-2 if it does not). Basin margin profile will dictate whether lowstand fluvial systems feed submarine fans (shelf-slope break profile) or detached shorelines (forced regressions on ramp margin). A conceptual model presented here, proposes that in structurally active extensional domains the expressions of eustatic sea-level change are still present in the stratigraphic record. These expressions are modified by complex basin margin topography and by significant, along strike variations in subsidence and accommodation creation. This model also illustrates that tectonically complex basins can host a spectrum of time equivalent lowstand deposits previously considered to be spatially and mutually exclusive. This model is illustrated by an example from the Oxfordian of the UK North Sea Central Graben.