Influence of Buried Mass-Transport Complexes on the Initiation and Evolution of Turbidity Currents

Slope failures and turbidity currents are the most common subaqueous processes and are ubiquitous on all continental margins. Their deposits mass-transport complexes (MTCs) and turbidites commonly co-occur and constitute key infilling elements of sedimentary basins. In this study, we use 3D seismic reflection data from the Taranaki Basin, northwest New Zealand, to investigate how a buried MTC influences the initiation, emplacement, and evolution of subsequent turbidity currents. We interpreted a buried MTC (MTC-1) that contains large transported blocks with well preserved internal reflections and adjacent debrites with chaotic to transparent seismic facies. We reveal that differential compaction driven by rheological contrasts between the blocks and debrites produced a rugose MTC top surface with local relief and asymmetrical depressions. This inherited relief locally enhances flow confinement and slope variability, promoting turbidity current acceleration and repeated hydraulic jumps across local depressions, thereby facilitating transitions to supercritical flow and the development of cyclic steps. Cyclic steps recur on successive stratigraphic surfaces above MTC-1 up to the modern seabed, indicating that inherited MTC relief continued to influence turbidity current over an extended geological timescale. Additionally, retrogressive failure associated with MTC emplacement generated fault-bounded, trough-like depressions in the headwall of MTC-1. These negative-relief features are interpreted to reorganize incoming turbidity currents through reflection and deflection, trapping flow within the trough and progressively focusing near bed transport along the trough axis, ultimately promoting channel incision and initiating a new channel pathway that is oriented approximately perpendicular to the original flow direction. Given that MTCs and turbidity currents are ubiquitous in subaqueous environments, and that differential compaction and retrogressive failure are common features of MTCs. We therefore indicate that combined effects of differential compaction and retrogressive failure exert a fundamental control on deep-water sediment distribution and stratigraphic architecture in deep-water systems.