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Plate-tectonic reconstruction of the southern Pacific and West Antarctica

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Citation:
Gohl, K. and Eagles, G. (2005): Plate-tectonic reconstruction of the southern Pacific and West Antarctica , 2nd International Alfred Wegener Symposium, 30 Oct - 2 Nov 2005, Bremerhaven, Germany. .
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Abstract:

Accurate plate-kinematic reconstructions at relatively high spatial and temporal resolution are the basis for understanding the opening of ocean basins and the evolution of seafloor relief and the effect it has had on controlling deep ocean current directions. We developed an animated, grid-based plate-kinematic reconstruction of the southern Pacific Ocean from 90 Ma to present, using the satellite-derived gravity anomaly field, and interpolated isochrons and plate rotation parameters from both published and new studies using marine geophysical data. The earliest opening with formation of seafloor between Chatham Rise (New Zealand) and Thurston Island (West Antarctica) occurred at 92-90 Ma along a Pacific-Antarctic plate boundary developing along the Bounty Trough and Great South Basin of New Zealand. The break-up between Campbell Plateau and Marie Byrd Land began at 83 Ma. The onset of an independent motion of the Bellingshausen Plate adjacent to the West Antarctic margin can be estimated at 79 Ma. Its motion generated a transpressional eastern plate boundary. The Pacific-Bellingshausen spreading centre developed a set of long offset transform faults (e.g. Udintsev, Tharp, Heezen) that the Pacific-Antarctic plate boundary inherited around 61 Ma when the Bellingshausen plate ceased to move independently as part of a Pacific-wide plate tectonic reorganization event. Southwest of these transforms, the Pacific-Antarctic Ridge saw an increase in transform-fault segmentation by about 58 Ma. At about 47 Ma, the Pacific-Phoenix Ridge jumped northward to directly link the Pacific-Antarctic ridge to the Pacific-Farallon ridge as a result of an unstable Pacific-Antarctic-Phoenix triple-junction configuration. Further reconstruction time steps illustrate the development of the dominant transform and fracture zones systems in the South Pacific.

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