Figure 1. Regional map of the Southeast Indian Ocean showing magnetic lineations (Cande et al., 1989), the Australian-Antarctic Discordance (AAD), and DSDP sites that sampled basement. Thin dark "V" to the east of the AAD is the inferred trace of the isotopic boundary for a migration rate of ~40 mm/yr. The broader gray "V" is the approximate trace of the regional depth anomaly (from Pyle et al., 1995). Bulls-eyes south of Australia indicate approximate positions of dredges by Lanyon et al. (1995).

Figure 1

Perspective view (in color), looking northeast across Segment B5, the easternmost AAD segment, to Zone A. Note the contrast between elevated, chaotic seafloor in the foreground and normal, lineated abyssal hill terrain beyond. The former is formed by largely amagmatic spreading over Indian mantle, the latter by more normal spreading over Pacific mantle. Single pink line marks the Indian-pacific boundary on B5. Double line is the B5 spreading axis. (See Christie et al.; 1998 for details.)

Figure 1 (Color)

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