Harya Nugraha

Taking a Closer Look at Mass-transport complexes (MTCs): Their Dynamics and Architecture

Harya Nugraha

Mass-transport complexes (MTCs) are common features in deep-marine environments. Their emplacement can catastrophically displace sediment to continental slope and basin floor, and have a direct impact on society by generating tsunamis and destroying offshore infrastructure. The proliferation of high-resolution multibeam bathymetry and three-dimensional seismic reflection data have improved our understanding of their internal form and emplacement processes. However, uncertainties remain in terms of: (i) how the volume and flow behaviour of MTCs evolve during their translation, and what controls these changes; (ii) how strain is distributed within MTCs, and its relationship to their internal architecture and geometry; and (iii) what are the implications of MTC emplacement processes for geohazard risk and petroleum system assessments in sedimentary basins. To address these problems,three-dimensional seismic reflection, well, and bathymetry data from the Exmouth Plateau (offshore NW Australia) and the Makassar Strait (offshore Indonesia) are used. This study demonstrates that: (i) dynamic interaction between mass flows and substrate lead to the final volume is three times the initially evacuated volume on average, and the formation of intra-MTC flow cells that can translate with a different speed and runout distance; (ii) strain distribution of an MTC is variable along strike, resulting in the variations of internal architecture and frontal geometry, partly controlled by the basal shear surface depth and morphology; and (iii) changes in MTCs volume and flow behaviour should be considered for tsunami and impact modelling, and heterogeneity of MTCs should be characterised when evaluating their reservoir and seal potential for hydrocarbon systems.