Evolution of the Malvinas Plate South of Africa |
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| Authors: | Marks KM Stock JM |
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| Institution: | (1) NOAA Laboratory for Satellite Altimetry, Silver Spring, MD 20910, USA;(2) Seismological Laboratory, California Institute of Technology, Pasadena, CA 91125, USA |
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| Abstract: | We confirm that a Malvinas Plate is required in the Agulhas Basin during the Late Cretaceous because: (1) oblique Mercator
plots of marine gravity show that fracture zones generated on the Agulhas rift, as well as the Agulhas Fracture Zone, do not
lie on small circles about the 33o-28y South America-Africa stage pole and were therefore not formed by South America-Africa
spreading, (2) the 33o-28y South America-Africa stage rotation does not bring 33o magnetic anomalies on the Malvinas Plate
into alignment with their conjugates on the African Plate, and (3) errors in the 33o-28y South America-Africa stage rotation
cannot account for the misalignment. We present improved Malvinas-Africa finite rotations determined by interpreting magnetic
anomaly data in light of fracture zones and extinct spreading rift segments (the Agulhas rift) that are clearly revealed in
satellite-derived marine gravity fields covering the Agulhas Basin. The tectonic history of the Malvinas Plate is chronicled
through gravity field reconstructions that use the improved Malvinas-Africa finite rotations and more recent South America-Africa
and Antarctica-Africa finite rotations. Newly-mapped triple junction traces on the Antarctic, South American, Malvinas, and
African Plates, combined with geometric and magnetic constraints observed in the reconstructions, enable us to investigate
the locations of the elusive western and southern boundaries of the Malvinas Plate.
This revised version was published online in November 2006 with corrections to the Cover Date. |
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| Keywords: | Agulhas Basin gravity anomalies Late Cretaceous Malvinas Plate plate tectonics reconstruction South Atlantic Ocean |
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