What Is the
Shelf Break?
Donovan, Art1 (1) BP,
Probably no term in sequence stratigraphy
is more important or misunderstood then “Shelf Break”. Through time this term
has been variably used to define the physiographic relief associated with shorelines,
sequence boundaries, maximum regressive surfaces, and continental margins.
Since sequence models, and fan plays, are tied to this concept, the ability to
clearly articulate and differentiate the wide variety of uses is critical.
The terms depositional topset, foreset,
and bottomset can be used to convey the topography associated with the
shoreline profile at any point in time. Within this paradigm, the depositional
shoreline break marks the physiographic break between the depositional topset and
foreset, while the depositional foreset break marks the physiographic break
between the depositional foreset and bottomset. The terms Relict Shelf and
Slope Breaks can be used to convey relict physiographic breaks associated with
major progradational episodes positioned inboard of the continental margins, or
in lacustrine basins. The terms Depositional Shelf and Slope Breaks can be used
to define the physiographic breaks along depositional sequence boundaries. The
terms Continental Shelf and Slope Breaks can be used to convey relict
physiographic breaks associated with the continental margins.
Through time, a depositional shoreline
break may prograde beyond a Relict or Continental Shelf Break. A cratonic fan
play can develop along sequence boundaries developed outboard of Relict Shelf
Breaks in epicontinental seas and continental shelves, while a lacustrine fan
play can develop similarly in lakes. An ocean basin fan play can develop along
sequence boundaries developed outboard of Continental Shelf Breaks.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California