Читать книгу Continental Rifted Margins 1 - Gwenn Peron-Pinvidic - Страница 28

The lithospheric mechanisms that accommodate extension can be roughly divided into three categories: pure shear, simple shear and crustal flow (Figure 1.13). Pure shear refers to a homogeneous flattening of a rock body that is elongated in one direction and shortened perpendicularly. First applied by McKenzie (1978) to regional rift settings, this mechanism assumes that the lithosphere deforms uniformly. Simple shear is a deformation mode involving a rotational component, in which parallel markers in a rock body remain parallel while translating relative to each other. (see Chapter 2 for further description of the models applied to rift settings). Numerical, analogue and conceptual models have been developed and tested based on these core mechanisms. Even though each deformational mechanism is based on an idealized version of the lithospheric structure and rheology, they are considered to represent most of the structural settings encountered on Earth.

Figure 1.13. Illustration of the pure shear and simple shear deformation mechanism (source: modified after Fossen 2010)