High-resolution animated tectonic reconstruction of the South Pacific and West Antarctic margin


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geagles [ at ] awi-bremerhaven.de

Abstract

An animated reconstruction shows an interpretation of South Pacific platekinematics between 90 and 45 Ma, using the satellite-derived gravityanomaly field, and interpolated isochrons and pole parameters from bothpublished and new work on marine geophysical data. Extension in the GreatSouth Basin and Bounty Trough, New Zealand, may mark an early Pacific-Antarctic plate boundary that replaced eastern parts of the Phoenix-PacificRidge and Phoenix-Antarctic subduction zones after collision of theHikurangi Plateau with the subduction zone. The earliest Pacific-Antarcticseafloor formed within the eastern parts of this zone, but later and furtherwest it formed within the Antarctic flank. After 80 Ma, the Bellingshausenplate converged with an oceanic part of the Antarctic plate, captured from anearlier "Charcot" plate, while simultaneously developing a rift withincontinental Antarctica - possibly in Peacock Sound. The Pacific-Bellingshausen spreading centre developed long-offset transform faults atthe Udintsev, Tharp and Heezen fracture zones. Around anomaly C27(61 Ma), the Bellingshausen plate ceased to move independently and platemotions altered. The Amundsen Sea sector of the Pacific-Antarctic Ridgesaw an increase in segmentation by transforms by 58 Ma. The long-offsettransforms of the former Bellingshausen-Pacific spreading centre did notmultiply but may have undergone some transpressional deformation. Afteran interpolated age of about 64 Ma, a long-offset transform, referred to as"V", formed as the Pacific-Phoenix arm of the Pacific-Bellingshausen-Phoenix triple junction. A Pacific-Antarctic-Phoenix triple junction wasinitiated on the southern edge of "V" in the C27 event. Eastern parts of "V"continued to operate in the Pacific-Phoenix spreading system and itslengthening western parts operated in the Pacific-Antarctic system. "V"was by-passed and deactivated by a ridge-axis propagation event to itsnorthwest at ~47 Ma.



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Eprint ID
9633
DOI 10.1029/2003GC000657

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Eagles, G. , Gohl, K. and Larter, R. D. (2004): High-resolution animated tectonic reconstruction of the South Pacific and West Antarctic margin , Geochemistry Geophysics Geosystems, 5, Q07002 . doi: 10.1029/2003GC000657


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