Seismic character and interaction of \ud intrabasinal mass-transport deposits in \ud deep-water continental margins \ud (Espírito Santo Basin, SE Brazil)

Doctoral thesis English OPEN
Omosanya, Kamaldeen
  • Subject: QE

The aim of this thesis is to assess the spatial and temporal recurrence of mass-transport \ud deposits (MTDs) within salt withdrawal basins to unravel the complex interaction \ud between mass-wasting processes and salt halokinesis. A high-quality 3D seismic dataset \ud from the mid-continental slope of Espírito Santo Basin, SE Brazil, was used to assess \ud the provenance of mass-transport deposits and their potentials as structural markers for \ud seafloor perturbation and fault activity. \ud \ud A new proposition from this work includes scale-independent classification of mass-\ud transport deposits into homogeneous and heterogeneous types. Heterogeneous MTDs \ud are composed of seismic facies corresponding to slides, slumps and debrites. \ud Homogeneous MTDs comprise consolidated debrites considered in this work as \ud comprising barriers to fluid flow. In addition, MTD composed of rafted blocks \ud displayed a disproportionate relationship between their shape, transporting distance and \ud degree of remobilization. \ud \ud Drag zones denote sections of MTDs that are uplifted during salt diapir rise. These drag \ud zones are extended and shortened along their long and short axis respectively. Ramps \ud flanking salt diapirs are formed by either complete or partial erosion of paleo-seafloors \ud and pre-existing fault scarps. In this thesis, it is shown that the risk of remobilized \ud sediments is highest within drag zones. \ud \ud The erosive nature of mass-wasting processes is justified by the decoupling history of \ud faults eroded by MTDs. An innovative method to assess fault decoupling history on \ud continental margin is the use of cumulative throw character. MTD-decoupled faults are \ud iv | P a g e \ud \ud characterised by shorter propagation rate and cumulative throw and are potentially \ud sealing compared to their non-decoupled counterparts. \ud \ud The information from this study is crucial information for successful hydrocarbon \ud exploration and risk assessment in deep-water environments. The methodologies and \ud results from this thesis are applicable to continental margins worldwide.
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