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Finch, Emma1, Rob Gawthorpe1, Ron Steel2, Steen Petersen3
(1) University of Manchester, Manchester, United Kingdom
(2) The University of Texas at Austin, Austin, TX
(3) Norsk Hydro Research Centre, Bergen, Norway

ABSTRACT: Seismic Expression of High-Frequency Shelf-Edge to Basin Floor Depositional Systems and their Sequence Stratigraphic Subdivision: Eocene of Spitsbergen

A series of seismic-scale (30 km long x 500-750 m high) clinoform exposures of Eocene age in Spitsbergen’s Central Basin have been used to examine the seismic expression of clinoforms and their sequence stratigraphic evolution. In particular, we investigate the 2D seismic character of various shelf-edge, slope and basin floor reservoir classes developed within 20 high-frequency (4th order) clinoform units. The shelf-slope-basin floor clinoforms indicate water depths of up to 500 metres, slope lengths up to 5 km, slope gradients up to 3 degrees, and basin-floor fans extending away from the slope up to 10 km.
Discrete sedimentary packages from the 20 high-frequency clinoform units recognised in the Spitsbergen exposures have been used to generate 2D synthetic seismic sections. At typical exploration frequencies (30-40 Hz), the synthetic seismic sections only allow subdivision of the clinoform units into low-order packages on the basis of changes in the trajectory of the shelf-edge. Even within this low-order seismic stratigraphic framework, large-scale basin-floor fans associated with intervals of flat progradation or basinward-falling shelf-edge trajectory, as well as distinct late progradational shelf-edge wedges (late lowstand) can be recognised. However, much of the stratigraphic detail allowing linkage of reservoir distribution to clinoform geometry at outcrop cannot be resolved. At frequencies >70 Hz, sequence stratigraphic division of the clinoforms at a scale similar to the 20 high-frequency outcrop units is achievable. Furthermore, sand-prone incised valleys at the shelf-edge and incised slope channels are resolvable allowing detailed sub-division of the high-frequency clinoforms into component systems tracts.


AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.