Rifting of young oceanic lithosphere imaged at the Rodriguez triple junction

What is it about?

The Indian Ocean Triple Junction, otherwise known as the Rodriguez Triple Junction, is the point where the African, Indo-Australian and Antarctic plates meet. It is also where the Central Indian Ridge (CIR), Southwest Indian Ridge (SWIR) and Southeast Indian Ridge (SEIR) meet. From earlier work, the triple junction was expected to be a ridge-ridge-ridge type (three ridges meeting at a point). In this article, the detailed pattern of abyssal hills (formed by faulting and volcanism at the ridges) was mapped out. A set of normal faults was found at the easterly end of the SWIR crossing the seafloor spreading fabrics previously formed at the CIR. The unusual geometry of the triple junction therefore revealed the spatial distribution of faulting about the SWIR, which is the slowest of the three spreading centres. The full relief of the SWIR rift valley does not develop until ~35 km from the triple junction, effectively forming a continuous or discontinuously propagating rift into seafloor formed at the other two ridges.

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Why is it important?

The spatial distribution of faulting about mid-ocean ridges is still not well resolved from morphologic data, though better estimates are available from seismology. This is a rare example of the spatial distribution of faulting being resolved.