Kerguelen Plateau crustal structure and basin formation from seismic and gravity data

Abstract

We use multichannel seismic data, gravity, and subsidence modeling, in conjunction with plate reconstructions, to evaluate the crustal origin and composition of the Kerguelen Plateau. Predominantly oceanic crust of the southern and parts of the central Kerguelen Plateau appears to include continental fragments related to the breakup of India and Antarctica; these fragments may have been metamorphosed during emplacement of the main plateau. The upper crust is basaltic, the middle crust is intrusive mafic rock and intruded continental crust, and the lower crust is a plagioclase-rich metamorphic rock. The Labuan Basin crust is predominantly oceanic with stranded Kerguelen Plateau fault blocks. High-density lower crust in the Labuan Basin is probably composed of serpentinized peridotites formed during slow rifting and spreading. Plate reconstruction models indicate opening between eastern Broken Ridge and southern Kerguelen Plateau at ∼90 Ma, heralding the formation of the Labuan Basin and Diamantina Zone; crustal attenuation and slow accretion of oceanic crust continued until the Australian and Antarctic plates separated at CIS time (∼40 Ma). Plate reconstructions of the free-air gravity field indicate that the Naturaliste Plateau fits against Antarctica and that Elan Bank and India were juxtaposed until ∼110 Ma. Both Naturaliste Plateau and Elan Bank are probable microcontinents. A ∼1 km positive residual depth anomaly in the oceanic basins adjacent to the plateau, along with the positive geoid anomaly centered beneath the northern Kerguelen Plateau, imply that the lithosphere is partially dynamically supported by an upwelling hot asthenosphere of the Kerguelen hot spot. Copyright 2001 by the American Geophysical Union.