--> ABSTRACT: Turbidite Paradigm and Sequence Stratigraphy - A Critical Perspective, by G. Shanmugam, R. J. Moiola, and J. B. Wagner; #91021 (2010)

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Turbidite Paradigm and Sequence Stratigraphy - A Critical Perspective

SHANMUGAM, G., R. J. MOIOLA, and J. B. WAGNER

The basic tenets of the turbidite paradigm and sequence stratigraphy are that deep-water sands are predominantly a product of turbidity currents, and that submarine-fan models with channel/levee and lobe elements are the norm. The reality, however, is that deep-water systems are extremely complex and variable. Recent studies show that deposits of debris flows, slumps, and bottom currents are far more important than deposits of turbidity currents in many hydrocarbon-bearing sandstone reservoirs (offshore Equatorial Guinea, offshore Nigeria, North Sea, Gulf of Mexico). Some critical perspectives are: (1) Sedimentary features in deep-water deposits reflect processes of deposition, not processes of transportation. (2) "Bouma Sequences" can be produced by processes other than turbidity currents. (3) High-density turbidity currents contain traction carpets and therefore should be classified as sandy debris flows. (4) The customary interpretation of any deep-water sand as a turbidite inappropriately results in a submarine-fan interpretation. (5) Sediment-gravity flows can occur during periods of both falling and rising sea levels in the deep sea due to earth quakes, shelf-edge failures, and seeping gas hydrates. (6) The concepts of "marine-flooding surface" and "parasequence", reflective of changing water depths, are not meaningful for deep-water (bathyal) sands that can be emplaced in a matter of hours or days. (7) Seismic geometries and log motifs are not reliable indicators of depositional facies. (8) Distinguishing autocyclic processes (e.g., slump scar) from those of allocyclic processes (e.g., sequence boundary) are difficult in seismic profiles. (9) Existing sedimentologic and sequence stratigraphic fan models are not suitable for debris-flow dominated systems.

AAPG Search and Discovery Article #91021©1997 AAPG Annual Convention, Dallas, Texas.