Geometry of the younger sediment bodies of the Indus Fan

Abstract

The younger channel-levee systems of the very large Indus Fan are mapped with GLORIA sidescan sonar records and seismic profiles. Thirty-five new cores have been obtained. The distributary pattern is more highly developed than on other known submarine fans. A distributary complex of large channel-levee systems with a radial pattern is found at the mouth of individual canyon complexes. They feed a lower order of distributary complexes, also with a radial pattern of small channel-levee systems. As on other fans only one channel is active at a time. The relative ages of this hierarchy of channel-levee systems is determined by superposition seen on seismic profiles and by measurements of the increasing thickness of the supposed hemipelagic mud drape that overlies the turbidite sequences. For the smaller channel-levee systems the avulsion is an internal (autocyclic) process, but some of the larger systems may form in successive periods of low sea level. Relative to other turbidite systems the maximum channel gradients are low, less than 1 in 200, and maximum sinuosity is high, greater than 3.