PESA SA/NT October Technical Luncheon – Thursday, October 28th: Controls on gravity-driven normal fault geometry and growth in stacked deltaic settings: a case study from the Ceduna Sub-basin

Summary:

Kinematics of gravity-driven normal faults exerts a critical control on petroleum systems in deltaic settings but to date have not been extensively examined. The Ceduna Sub-basin (CSB) is a passive margin basin containing the White Pointer (Albian-Cenomanian) and Hammerhead (Campanian-Maastrichtian) delta systems that detach on shale layers of Albian-Cenomanian and Turonian-Coniacian ages, respectively. We present evidence for spatially variable fault growth styles based on interpretation of the Ceduna 3D seismic survey and fault kinematic analyses using displacement-distance, displacement-depth, and Expansion Index methods. We identified faults that continuously grew either between the Cenomanian-Santonian or Santonian and the Maastrichtian located throughout the study area, and faults that exhibit growth between the Cenomanian-Maastrichtian that are geographically separated into three areas according to their evolution histories: (i) Northern CSB faults exhibit constant growth between the Cenomanian and Maastrichtian. (ii) Central CSB faults show two dip linkage intervals between (a) Cenomanian and Coniacian-Late Santonian, (b) Coniacian-Late Santonian and Late Santonian–Maastrichtian segments, respectively. (iii) Central and southern CSB faults exhibit dip-linkage intervals between Cenomanian-Early Santonian and Late Santonian-Maastrichtian segments. Our study demonstrates a relationship between the location of the Cenomanian-Maastrichtian faults and their evolution history suggesting constant growth evolution at north and dip-linkage at the central and south areas.