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 extension direction significantly affected the structure of the transform faults, when in the period 69–52 Ma it was successively undergone to transtension and transpression, forming multiple bends in its fault zones. A physical modeling 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 have formed under certain combined conditions, the most important of which are (i) the obliquity of the transform fault system to the extension direction, (ii) the length of the fault segments, and (iii) the ratio of the fault segment length to the spreading segment length. The experimental results suggest the evolution of fault zone 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 transpressional conditions, in which the multitransform system gradually turns into a single oblique transform fault influenced by a gradual decrease in the length of intertransform spreading segments. The possible formation of intertransform ridges observed within the Andrew Bain Fault Zone, 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 India-Eurasia collision.