Linking Sediment Transport and Stratigraphy on the Continental Shelf

Patricia Wiberg,Donelson Wright,David Cacchione,Richard Sternberg

doi:10.5670/oceanog.1996.02

Abstract

T H E GOAL OF THE SHELF sediment dynamics component of STRATAFORM is to link sediment transport processes active on the continental shelf to the formation and preservation of beds in shelf sediment deposits. An approach combining shelf sediment-transport models with high-resolution measurements of water-column and properties over periods from several months to several years allows us to make quantitative estimates of modification caused by sediment resuspension during episodic transport events. These modifications include erosion and deposition of material, formation of graded storm beds, and changes in small-scale surface morphology. The characteristics of the resulting event bed (thickness, grading, physical structures) are a function of flow and properties, depending on both temporal and spatial variations in sediment transport. Sediment transport on the continental shelf depends on surface-wave conditions, bottom-boundary-layer currents, fluid stratification, and characteristics, including grain size, density, porosity, and surface roughness. In general, sediment transport rates and depths of reworking are greatest when large, long-period waves occur simultaneously with strong, persistent currents. Thus understanding the magnitude and frequency of transport requires knowledge of the wave and current conditions on the shelf over sufficiently long periods of time to develop statistical characterizations of the wave and current fields and to document the resulting resuspension and modification. This information also provides critical

Highlights

T H E GOAL OF THE SHELF sediment dynamics component of STRATAFORM is to link sediment transport processes active on the continental shelf to the formation and preservation of event beds in shelf sediment deposits
The time series of suspended-sediment concentration illustrates the energetic nature of the Eel continental shelf and the significant sediment response
Over the first 45-day record, 13 identifiable sediment suspension or transport events occurred, each lasting an average of -2 days

Summary

Introduction

T H E GOAL OF THE SHELF sediment dynamics component of STRATAFORM is to link sediment transport processes active on the continental shelf to the formation and preservation of event beds in shelf sediment deposits. Measurements of small-scale surface roughness elements and of the characteristics of the uppermost 10-20 cm of the bed, including sediment texture and physical and biogenic structures, before and after a transport event such as the one shown, are being collected to document processes such as bed reworking and bedform migration (Wheatcroft et al, 1996, this issue).

Results

Conclusion