Rheological-Layered Basin Under Strike-Slip Deformation: Analogue Approach At Crustal Scale

In sedimentary basins, sediment type and deposit and burial conditions generate successive layers with various rheologies reacting differently to boundary stresses. We used analogue modelling to explore how a rheological-layered basin reacts to strike-slip displacements applied to boundaries. Several experimental set-ups were tested by varying horizontal rheological layering (alternating viscous and cohesive layers) and displacement rates. All experiments generated a complex three-dimensional deformation pattern localized into a narrow vertical band with thickened, thinned and folded domains alternating along both strike and depth. This results in a succession of positive and negative flower structures connected to the basal velocity discontinuity at depth and in a decoupling of deformation from one layer to another. Thinning and thickening variations display an along-strike wavelength proportional to the layer thickness, an amplitude controlled by rheological layering, and in particular the strength contrast between each layer. The simultaneous genesis of shortening and stretching structures during only one deformation stage is symptomatic of strike-slip boundary conditions. These results indicate that caution should be exercised when postulating polyphased deformation from overprinting of different deformation styles.