Evolution of the Southwest Indian Ridge from 55°45′E to 62°E: Changes in plate‐boundary geometry since 26 Ma

2007/06/01 by A. Graham Baines, M. J. Cheadle, H. J. Dick +4 · 50 citations
Earth and Planetary Sciences · #earthquake and tectonic studies #Geological and Geochemical Analysis #Geology and Paleoclimatology Research #Geology #Transform fault #Classification of discontinuities #Seafloor spreading #Mid-ocean ridge #Ridge #Seismology #Echelon formation #Magnetic anomaly #Bathymetry #Clockwise #Plate tectonics #Geometry #Mantle (geology) #Lineation #Offset (computer science) #Geodesy #Upwelling #Oblique case #Rotation (mathematics) #Fault (geology) #Geophysics #Tectonics #Paleontology

paper · open access · doi:10.1029/2006gc001559

published in Geochemistry Geophysics Geosystems 8(6) (Wiley)

openalex publication_date 2007/06/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/08

Abstract

From 55°45′E to 58°45′E and from 60°30′E to 62°00′E, the ultraslow‐spreading Southwest Indian Ridge (SWIR) consists of magmatic spreading segments separated by oblique amagmatic spreading segments, transform faults, and nontransform discontinuities. Off‐axis magnetic and multibeam bathymetric data permit investigation of the evolution of this part of the SWIR. Individual magmatic segments show varying magnitudes and directions of asymmetric spreading, which requires that the shape of the plate boundary has changed significantly over time. In particular, since 26 Ma the Atlantis II transform fault grew by 90 km to reach 199 km, while a 45‐km‐long transform fault at 56°30′E shrank to become an 11 km offset nontransform discontinuity. Conversely, an oblique amagmatic segment at the center of a first‐order spreading segment shows little change in orientation with time. These changes are consistent with the clockwise rotation of two ∼450‐km‐wide first‐order spreading segments between the Gallieni and Melville transform faults (52–60°E) to become more orthogonal to spreading. We suggest that suborthogonal first‐order spreading segments reflect a stable configuration for mid‐ocean ridges that maximizes upwelling rates in the asthenospheric mantle and results in a hotter and weaker ridge‐axis that can more easily accommodate seafloor spreading.

Citations

• A Survey of the Southwest Indian Ridge Axis Between Atlantis II Fracture Zone and the Indian Ocean Triple Junction: Regional Setting and Large Scale Segmentation
• Magmato‐tectonic cyclicity at the ultra‐slow spreading Southwest Indian Ridge: Evidence from variations of axial volcanic ridge morphology and abyssal hills pattern
• Evidence for motion between Nubia and Somalia along the Southwest Indian ridge
• LEAST-SQUARES FITTING OF A STRAIGHT LINE
• New, improved version of generic mapping tools released
• Global Sea Floor Topography from Satellite Altimetry and Ship Depth Soundings
• Modes of seafloor generation at a melt-poor ultraslow-spreading ridge
• An ultraslow-spreading class of ocean ridge
• Evolution of the Indian Ocean Triple Junction between 65 and 49 Ma (anomalies 28 to 21)
• Abyssal peridotites, very slow spreading ridges and ocean ridge magmatism
• Effect of recent revisions to the geomagnetic reversal time scale on estimates of current plate motions

Cited by

• Jurassic zircons from the Southwest Indian Ridge
• From slow to ultra-slow: How does spreading rate affect seafloor roughness and crustal thickness?
• Southwest Indian Ridge [wikipedia]