--> Sea Level Controls on Deepwater Sedimentation: Lessons From the Quaternary of the Indus Canyon

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Sea Level Controls on Deepwater Sedimentation: Lessons From the Quaternary of the Indus Canyon

Abstract

The Indus River supplies sediment to one of the largest submarine fans on Earth. Most of this sediment is transported to the deep basin via the submarine canyon which insizes into the broad continental shelf. A series of cores taken along the axis of the canyon now allow us to reconstruct when sedimentation has been taking place during the last glacial cycle and from where that sediment is transported. Sedimentation has been continuous through the length of the canyon during rising and high stands of sealevel. Channel reorganization in the canyon is shown by the presence of a mid-Holocene oxbow, which was active until ∼7 ka. Sediment has continued to blanket terraces above the canyon as well as within the thalweg throughout the Holocene. Nd isotope data allow us to assess the source of the sediment, which is indistinguishable from that delivered by the river mouth since the early Holocene and in sharp contrast to the western shelf clinoform where recycling and longshore transport dominates. The large eastern clinoform likewise is built by direct flux from the river mouth. Our work suggests that the river has been supplying sediment into the deep canyon throughout the sealevel rise, although that the sediment has become more sandy after the stabilization of sealevel ∼6 ka. We suggest that climatically modulated sediment supply dominates over sealevel in controlling sediment flux to the deep ocean, although it is not apparent that this sediment is reaching the channel-levee complexes of the mid-fan.