James P. M. Syvitski¹, Damian B. O'Grady¹

(1) University of Colorado, Boulder, CO

ABSTRACT: Influence of Continental Catchments on the Morphology and Properties of Continental Margins

Rivers provide the primary method of sediment delivery to continental shelves, enabling identification of sediment-rich and sediment-starved margins. Recent analysis has shown that sediment delivery depends on catchment relief, area, and temperature. Sediment yield increases with basin relief. Cold polar climates do not produce as much sediment per unit area as hot tropical climates. Catchment area provides a fundamental control on the sediment concentration discharged by the rivers, with small basins discharging the most turbid water. The inter- and intra-annual fluctuations in sediment delivery are controlled by weather systems, basin characteristics, climate and hydrology. Very large rivers offer less variability, in contrast to smaller rivers. Small rivers often have a high coherency between their floods and shelf storms; large rivers often delivery sediment during periods of ocean quiescence. Rivers supply the buoyancy control on the nature (hyperpycnal vs. hypopycnal) of their plumes. Recent evidence points to more rivers able to generate hyperpycnal plumes during flood conditions. Rivers supply the initial momentum to disperse the sediment load, an important aspect of large rivers, and for small rivers undergoing flood conditions. Recent analysis of global data on the morphology of continental margins shows that the shape of a margin's clinoform is strongly influenced by the amount of sediment reaching the continental slope. Continental slopes seaward of rivers with high sediment load tend to have more gentle slope gradients and fewer submarine canyons than those seaward of lower sediment discharge rivers. Additionally the depth of the receiving basin provides a fundamental feedback and influence on margin morphology. Recent numerical experiments confirm this feedback between sediment delivery from the continent and ocean depth, and the resulting architecture of the sedimentary system.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado