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ABSTRACT: Plate Tectonic Development of the Marginal Basins of the Southwest Pacific

Loren W. Kroenke, Chin-yeung Chan

A series of palinspastic maps have been constructed that are believed to closely portray the Cenozoic paleogeography of the Southwest Pacific. Combining newly determined rotation vectors for the Indo-Australia (I-A) and Pacific (P) plates, as well as poles of opening, spreading rates, and paleo-plate boundary locations for the marginal basins of the Southwest Pacific, major physiographic features on the I-A and P plates have been tracked northward relative to fixed hotspots on both plates from 55 Ma to the present. Major changes in plate motion appear to have occurred concomitant with collision tectonism and formation of new trenches at: ^sim55 Ma (Aure-Moresby-Rennell-New Caledonia Trench), ^sim43 Ma (Manus-North Solomon Vitiaz), ^sim25 Ma (Wewak-Trobriand and Lau trench s), and ^sim10 Ma (New Britain-San Cristobol-New Hebrides and Tonga-Kermadec trenches). Episodes of marginal basin formation have occurred in the back-arc regions along the eastern and northeastern margins of the I-A plate between 81-53 Ma (Tasman basin), 63-53 Ma (Coral Sea basin), 52-40 Ma (Loyalty basin), 33-28 Ma (D'Entrecasteaux basin), 34-26 Ma (South Fiji basin), 10-0 Ma (North Fiji basin), 6-0 Ma (Lau basin), 5-0 Ma (Woodlark basin), and 3-0 Ma (Manus basin). Basin formation has resulted in rotation, fragmentation, and severe dislocation of volcanic arcs. Reactivation of older subduction zones, briefly rejuvenating arc volcanism, has also occurred sporadically throughout the Cenozoic.

AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990