Evolution of the Du Toit–Andrew Bain–Marion–Prince Edward Transform Fault System (Indian Ocean): Physical Modeling of Structural and Kinematic Changes in the Late Cretaceous–Paleocene

The Du Toit–Andrew Bain–Marion–Prince Edward transform fault system separates two parts of the Southwest Indian Ridge that differ in structure and development. The change in the extension direction significantly affected the structure of the transform faults, when in the period 69–52 Ma it was successively subjected to transtension and transpression, which led to the formation of multiple bends in its fault zones. A physical modeling method was used to identify the conditions of structural changes and the evolution of the transform fault during this period. It was experimentally shown that a complex structural pattern could only form under a certain combination of conditions, the most important of which are (i) the angle of inclination of the transform fault system to the direction of extension, (ii) the length of the fault segments, (iii) the ratio of the length of the fault segments to the length of the spreading segments. The experimental results suggest the development of passive trace bends as a transtensional duplex, which is confirmed by the long existence of the structure and its self-development. Almost identical results were obtained under transtensional conditions, in which the multitransform system gradually transforms into a single oblique transform fault under the influence of a gradual decrease in intertransform spreading segments. The possibility of formation intertransform ridges observed within the passive traces of the Andrew Bain fault, which remained as a result of the rotation of lithospheric blocks, was shown in two experimental series. Sharp structural and kinematic changes in the fault zone may be the result of a major regional tectonic reorganization during the collision of the paleocontinents of India and Eurasia.