U. S. Geological Survey, United States

The cored record at Ocean Drilling Program Site 1122, located on the levee of the Bounty Fan off southeastern New Zealand, shows a major late Miocene to Pliocene (11.0-3.5 Ma) hiatus in sedimentation. This hiatus straddles a period of major uplift in the Southern Alps where the rivers that feed sediment to the Bounty Fan are ultimately sourced. There are no significant changes in sediment provenance across this interval. We link this hiatus to a combination of decreased sediment supply owing to tectonic disruption of fluvial drainage and a roughly simultaneous increase in bottom-current strength. Evidence for this scenario includes the distribution of current-generated structures in the core, the relative timing of an onshore transition from fluvial to lacustrine sedimentation, and a potential post-hiatus pulse of more weathered sediment into the Bounty Fan. This sediment pulse was possibly associated with the reestablishment of throughgoing drainage and the erosion and flushing of stored alluvial to lacustrine sediments through the system. Thus the Bounty Fan provides an excellent example of how the complex interplay between tectonic and paleoceanographic forces can affect the sedimentary record in deep-marine systems.