Long-Term
Delivery and Distribution of Sediments from River Catchments to Basin Floor
Fans
Sømme, Tor O.1, William
Helland-Hansen1, Ole J. Martinsen2, John B. Thurmond2
(1) University of Bergen, N-5007 Bergen, Norway (2) Norsk Hydro Research
Centre, N-5020 Bergen, Norway
To pursue a best-possible understanding
of deep-water subsurface reservoir distribution, investigation of quantitative
aspects of sediment delivery and storage along entire source-to-sink profiles
are required. 28 erosional-depositional systems associated with both active and
passive margins, and with different types of climate and basin morphology, have
been examined in order to identify the main controls on timing, volume and
spatial distribution of sediments delivered to and beyond the shelf break.
Detailed digital elevation models provided information on drainage and basin
parameters (e.g. length, gradient and area). Furthermore, an extensive
literature search gained further knowledge on sediment dispersal patterns and
basin floor fan characteristics.
Rivers are the primary source for
deep-water sediments, and a close relationship between the size and morphology
of a given drainage area, and the associated sediment load, transportation
pattern and volume of the deep-sea fan is shown. The link between the river
mouth and the shelf break is of primary importance in controlling sediment
dispersal, as the shelf functions as storage for river-fed material. Narrow and
steep shelves, strong littoral and tidal currents, and submarine canyons incising
the shelf are most important for sediment transport to the basin floor.
The maximum/minimum river discharge ratio
and sediment load variations, however, control sediment supply to the river
mouth. These factors operating within individual drainage areas are considered
as internal variables. The cross-sectional shape and plan-view morphology of
the source-, shelf- and basin floor transects are external factors, governing
long-term storage and transportation of sediments to basins.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California