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Multichannel seismic profiles with excellent resolution reveal the internal morphology of Miocene canyon-channel-levee systems in a part of the Indus submarine fan. Individual canyon-channel-levee systems may be correlated from profile to profile in a down-canyon direction for at least 160 km. Each canyon or channel complex consists of numerous smaller canyons or channels which have migrated, avulsed, and aggraded during a long complex history to produce the morphology observed in the seismic profiles.
Detailed examination of seismic lines over two canyon-channel-levee systems has resulted in the recognition of degradational, transitional, and aggradational zones, respectively, in a distal direction. The distribution of these zones and their associated processes is controlled by canyon-channel gradient. The degradational zone is characterized by an erosional base and is dominated by bank migrational deposits. The processes responsible for these deposits are poorly known. The transitional zone also has an erosional base but is marked by the presence of small levees. Deposition in this zone results from bank migration followed by channel-current and overbank processes. The aggradational zone is characterized by a depositonal base and large levees resulting from channel-current and ove bank processes which may include both sediment and fluid density flows. In each of the two canyon-channel-levee systems studied, aggradation has resulted in the gradual proximal displacement of the degradational, transitional, and aggradational zones.
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