The authors used three-dimensional (3D) seismic reflection data from the central Ceduna Sub-Basin, Australia, to establish the structural evolution of a linked normal fault assemblage at the extensional top of a gravitationally driven delta system.
The fault assemblage presented is decoupled at the base of a marine mud from the late Albian age. Strike-linkage has created a northwest–southeast oriented assemblage of normal fault segments and dip-linkage through Santonian strata, which connects a post-Santonian normal fault system to a Cenomanian-Santonian listric fault system.
Cenomanian-Santonian fault growth is on the kilometre scale and builds an underlying structural grain, defining the geometry of the post-Santonian fault system.
A fault plane dip-angle model has been created and established through simplistic depth conversion. This converts throw into fault plane dip-slip displacement, incorporating increasing heave of a listric fault and decreasing in dip-angle with depth. The analysis constrains fault growth into six evolutionary stages:
early Cenomanian nucleation and radial growth of isolated fault segments;
linkage of fault segments by the latest Cenomanian;
latest Santonian Cessation of fault growth;
erosion and heavy incision during the continental break-up of Australia and Antarctica (c. 83 Ma);
vertically independent nucleation of the post-Santonian fault segments with rapid length establishment before significant displacement accumulation; and,
continued displacement into the Cenozoic.
The structural evolution of this fault system is compatible with the isolated fault model and segmented coherent fault model, indicating that these fault growth models do not need to be mutually exclusive to the growth of normal fault assemblages.
Structure and morphology of the Bosumtwi impact structure from seismic reflection data