Morphostructure and evolution of submarine canyons across an active margin: Cook Strait sector of the Hikurangi Margin, New Zealand

Abstract

The Cook Strait sector of the Hikurangi Margin contains several canyons including New Zealand's largest canyon, the multi-branched shelf-indenting Cook Strait Canyon. The morphology of the canyons reflects the transition from subduction related thrust faulting to oblique collision and strike–slip faulting. High resolution EM300 multibeam and multichannel seismic reflection data reveal: i) widespread, deep-seated bedrock landsliding as a principal control on canyon enlargement; ii) a retrogressive entrenchment of tributary submarine catchments in response to a base-level perturbation which has rejuvenated canyons inferred to have been inactive as top to bottom sediment conduits since the last glaciation; and iii) the control of structurally generated bathymetric relief on both the routing of sediment pathways and the erosion of inter-canyon slopes. The models of canyon evolution demonstrated here have widespread implications for canyon development and evolution on other tectonically actively continental margins.