Print this pageRift Basin Evolution and the Generation of Low-angle Detachment Faults in Analogue Models
GARTRELL, ANTHONY P.
Analogue modelling techniques were used to investigate the evolution of extensional basins as part of a structural study of the North West Shelf of Australia. A multi-layer model of the lithosphere was constructed using a sand/clay mixture, quartz sand and two types of silicone putties. The models were extended under normal gravity forces in a process similar to slab-pull plate tectonics.
Although a wide range of three-dimensionally complex rift basins evolved, the following generalised structural evolution can be described: 1. Deformation is initially distributed over a broad block-faulted sag-basin. 2. Necking instabilities localise extension into narrow rift basins. The necks can be grossly symmetrical, resulting in full-graben architectures or highly asymmetrical, resulting in half-graben structures. High-angle normal faults in the brittle layer detach into low-angle brittle-ductile shear zones developed on the margins of the necks. 3. Necklines eventually tear, separating sections of the strong ductile lithospheric layer and causing the development of sub-horizontal detachments. Subsequent extension results in the formation of roll-over anticlines and associated crestal collapse graben. This stage is associated with rapid foot-wall uplift on the main displacement margins.
The evolution and structural architectures developed in the analogue models compare favourably with that of the field area. As a result the structural evolution and architecture of the field area was further refined by analogy with the experimental data.