Controls on sediment flux through the indus submarine canyon during the last glacial cycle

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Conference Proceeding

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© 2015 SEG. Classic sequence stratigraphic models argue that submarine canyons and their associated deep-sea fans should become inactive during periods of rising and high sealevel as accommodation space is generated on the continental shelf. Initial data from the upper Indus Submarine Fan had suggested that this system largely follows this model, as turbidite sedimentation ceased around 11 ka. New cores from the canyon now show that the situation is more complex, with sediment propagating deep through the shelf canyon during the entire Holocene. Sediment accumulation is known to be very rapid in recent times at the head of the canyon, but new 14C ages from foraminifera show that sandy sedimentation was ongoing in what is now an ox-bow cut-off -7 ka, while terraces up to 200 m above the thalweg have been blanketed by fine-grained sediments and sands since 9 ka. A core in the mid shelf canyon shows that sedimentation there has been rapid since at least 1000 yrs ago, and may have involved significant recycling, possibly from the depocenter at the canyon head. Nd and Sr isotopes now allow us to see that sediment in the canyon is of the same composition as that in the river mouth at the time of sedimentation. This raises the possibility that the river was supplying sediment to the canyon since at least 5 ka, shortly after eustatic sealevel stopped rising. This contrasts with the western shelf clinoform where sediment recycling from glacial age shelf sediment and long-shore current flow is important. Our data indicate that despite sealevel rise sediment supply to the canyon was not cut-off during the deglaciation, although the volume of the flux was reduced. We evaluate the roles played by sea level variations, sediment supply, and cyclones in feeding sediment into the canyon and assess the continuity of sandy channel fills. We suggest that enhanced sediment supply, driven by strong monsoon rains onshore compensated for the rising sealevel and allowed the connection between river and canyon to be maintained.

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SEG Technical Program Expanded Abstracts

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