The upper mantle beneath Ninetyeast Ridge and Broken Ridge, Indian Ocean, from surface waves

16. Magnetostratigraphy of Paleogene and Upper Cretaceous Sediments from Broken Ridge, Eastern Indian Ocean

Broken Ridge represents a fragment of the oceanic Kerguelen-Heard platform, constructed at high southern latitudes in the middle Cretaceous and rifted apart during the middle Eocene (43-45 Ma). The approximately 1400-m section of prerift sediments on Broken Ridge preserves a polarity sequence that spans the middle Eocene to Upper Cretaceous (Chrons Cl 8/C20 to C34), including a 500-m continuous...

Ridge-like lower mantle structure beneath South Africa

[1] Recent (ScS-S) results from probing the deep structure beneath southern Africa display strong delays of up to 10 s at distances beyond 90 . Such delays could be explained by long-period tomographic models containing smooth (weak) features with the addition of rough (strong) D00 structure (3–9% drops in shear velocities). However, these structures cannot explain the (SKS-S) differentials sam...

Upper mantle anisotropy beneath Peru from SKS splitting: Constraints on flat slab dynamics and interaction with the Nazca Ridge

Magmatic filtering of mantle compositions at mid-ocean-ridge volcanoes

Earth’s dominant form of magmatism occurs at mid-ocean ridges (MORs), producing the igneous crust for two-thirds of the planet’s surface and conveying significant heat and material fluxes from the mantle to the world’s oceans. Mid-ocean-ridge basalt (MORB) magmas form from upwelling compositionally heterogeneous mantle1 by aggregation of near-fractional melts beneath spreading centres2. Multipl...

Upper mantle structure beneath the eastern Pacific Ocean ridges

[1] We analyze vertical component body and surface waves for 10 Mw > 5 earthquakes, recorded by ocean bottom seismometers at regional and teleseismic distances. Through waveform modeling, we place new constraints on along-axis variation in temperature and partial melt beneath the eastern Pacific ridges. The resulting best fit models show over 9% variation in average lithosphere shear velocities...