Facies and Lithology Distribution Patterns Derived from Evolving Seismic
Geomorphologies Within a Seismic Stratigraphically Well
Constrained Submarine
Fan Complex
Frode Hadler-Jacobsen1, Michael H. Gardner2, and James
M. Borer2
1 Statoil ASA, Golden, CO
2 Colorado School of Mines,
Golden, CO
Spatial and temporal seismic stratigraphic trends document the deepwater
evolution in a small window (20-x30 km area) across the South Atlantic Margin.
Integration of seismic geomorphological (map) and architectural
(cross-sectional) analysis documents changes in confined (channel) and
unconfined (sheet) elements within a fourfold stratigraphic hierarchy of fan
cycles (2nd order through 5th order). With no direct borehole calibration
data
in the studied sub-basin, lithology prediction is based on (1) differential
compaction features indicative of lithogy contrast, (2) indirect
calibration
to
wells outside the South Atlantic Margin sub-basin of interest, and (3) analogue
comparison to Brushy Canyon 3D outcrop models documenting detailed lithology
distributions within a high-resolution stratigraphic hierarchy.
Three significant shifts in channel- and sheet-orientation and pattern are related to 2nd order tectonostratigraphic cycles recording the (c. 50my) basin margin evolution. 3rd order cycles show sets of sheet-channel couplets distributed in distinctly compensation patterns. 4th order cycles typically represent sheet-channel couplets repeated in predictable patterns of increasing channel-flank proportions and decreasing sheet proportion up stratigraphy. Individual (5th order) fan cycles, typically expressed as a single seismic loop, show a clear and predictable relationship to evolving seabed topography. Evolving seabed topography and gradients, related to the effect of basin margin evolution, produces predictable sheet and channel distributions within a fan cycle. Changes in channel orientation-, avulsion-, compensation-patterns and the position of channel mouths can be related to gradient changes within and between stratigraphic cycles.
AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005