HR: 1330h
AN: OS12A-0188    [PDF]
TI: Controls on Subaqueous-Delta Clinoform Development
AU: * Walsh, J
EM: jwalsh@ucsd.edu
AF: Scripps Institutions of Oceanography, Geosciences Research Division University of California, San Diego, La Jolla, CA 92093-0244 United States
AU: Driscoll, N W
EM: ndriscoll@ucsd.edu
AF: Scripps Institutions of Oceanography, Geosciences Research Division University of California, San Diego, La Jolla, CA 92093-0244 United States
AU: Nittrouer, C A
EM: nittroue@ocean.washington.edu
AF: School of Oceanography, Box 357940 University of Washington, Seattle, WA 98195-7940 United States
AB: Rivers discharge sediments and associated carbon to continental shelves around the world, and many factors are important to the dispersal of these materials. Seaward of some river mouths are subaqueous-delta clinoforms (SDC), and studies have identified a similar accumulation pattern associated with these morphological features (i.e., large sediment accumulation rates on foreset beds). This pattern and the geometry of SDC (i.e., the rollover point) are thought to be regulated by "wave base", the theoretical depth at which sediments are not resuspended. Quantitively, this can be viewed as the depth where critical bed-shear stress of sediment supplied is equaled by that from mean (tide-, wave- and current-dependent) transport conditions. As a result, wave base will vary on every continental margin, as will the potential for SDC development. To test this hypothesis and evaluate factors critical to SDC development, a GIS database with information on tidal range, mean significant wave height, river-sediment load, and continental-shelf width at $>$100 major river mouths was developed. These data combined with additional measurements from several marine river-dispersal systems indicate that SDC development requires a large sediment load ($\sim$100 million tonnes), significant tidal range ($>$2 m) and moderate wave climate ($>$1 m mean significant wave height). Also, strong correlations exist between tidal range and mean significant wave height and the distance and depth of nearest maximum shelf sediment accumulation, respectively. These relationships highlight the connection between transport conditions and SDC morphology. Sediment dispersal at the Margins Source-to-Sink focus areas, the Fly and Waiapoa rivers, supports these findings.
DE: 3022 Marine sediments--processes and transport
DE: 3045 Seafloor morphology and bottom photography
DE: 4219 Continental shelf processes
DE: 4860 Radioactivity and radioisotopes
DE: 4863 Sedimentation
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting