Outer forearc architecture and submarine landslides related to seamount subduction at the Hikurangi Margin (offshore New Zealand)

Sedimentation processes and tectonic mechanisms at the outer forearc of convergent margins are a subject of intense research, mainly owing to the inherent geological hazardous consequences associated with volcanism, seismic shaking, and gravitational mass movement. During the last decades, sample research has improved our knowledge of tectonics and sedimentation of a convergent margin as well as eruption history of backarc/arc volcanism. Parameters controlling tectonic erosion, sediment accretion, sediment architecture, and sediment instabilities of convergent margins are largely dependent on a multitude of geological conditions and have to be assessed individually for each case study. In this context, it is not only important to answer questions about the interaction of the overriding and subducting plates, but also about the temporal evolution of the continental margin and its response to changes in paleoclimatology. Studies undertaken in the framework of this doctoral project aim to contribute to answer the above developed questions by studying the sedimentation processes and stability of an accretionary ridge as well as the décollement at the Hikurangi Margin east off the North Island of New Zealand. The investigation area Rock Garden is an outermost sedimentary accretionary ridge in central Hikurangi Margin with an oversteep trenchward flank as a consequence of uplift above a subducting seamount. Studies presented in this thesis integrate high-resolution bathymetry and interface geometry of the subducting plate, high-resolution acoustic datasets with a wealth of data sets retrieved from drilled core material in order to address (1) the detachment strength and mechanical segmentation of the Hikurangi Margin, (2) the influence of seamount subduction and excess fluid pressure on slope failure, (3) the Quaternary marine tephrochronology of the frontal sediment accretionary ridge, and (4) patterns and cyclicity of Quaternary sediments at Rock Garden.


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