Structure and Sequence Stratigraphy of an Offshore Trench-Slope Basin—Comparison with a Field Analogue, Hikurangi Subduction Margin, New Zealand

Julien, Bailleul¹, Chanier Frank¹, Gorini Christian¹, Mahieux Geoffroy², Robin Cécile³, Ferriere Jacky¹ (1) UMR CNRS 8110 Lille University, Lille, France (2) UMR CNRS 8110 UPJV University, Amiens, France (3) Rennes University, Rennes, France

The initiation and evolution of trench-slope basins on subduction wedges are strongly related to subduction processes. These narrow elongated basins form on the lower trench slope, their edges consisting of structurally controlled linear bathymetric highs. In this par­ticular setting, sedimentary processes may be controlled by both tectonics and sea-level changes. Thus, the study of the sedimentary record can provide more accurate evaluation of the spatial and temporal contribution of tectonic activity on the development and strati­graphic evolution of trench-slope basins.

This study is based on a detailed stratigraphic analysis of the Titihaoa basin (Hikurangi subduction margin), offshore east coast of North Island, New Zealand. Compilation of seis­mic stratigraphic and wireline log (gamma ray and sonic) data, combined with lithostrati­graphic and biostratigraphic data obtained from well Titihaoa-1, allows to characterize major unconformities within the sedimentary infill of the lower trench slope. We interpret most of these unconformities in terms of sequence stratigraphy. On the bases of comparison with our results with onshore analogues, we propose a stratigraphic and structural conceptual model for trench-slope basin development taking into account 1) our geophysical study of the Titihaoa basin which permits to precise the role of deformation processes on the basin geometry and on sequence development and organisation, and 2) the analysis of the onshore Akitio basin which provides accurate descriptions and interpretations of turbidites facies and related deep-sea deposits with a focus on the evolution of sedimentary systems in response to changes in style and/or amplitude of tectonic activity.