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.