Is there a Caroline plate? |
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| Authors: | Jeffrey K Weissel Roger N Anderson |
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| Institution: | Lamont-Doherty Geological Observatory of Columbia University, Palisades, N.Y. 10964 U.S.A. |
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| Abstract: | We examine available marine geophysical and seismological data from the Caroline Sea region and conclude that a separate Caroline plate currently exists. The Caroline plate is moving relative to the Pacific plate on its northern and eastern boundaries, the Philippine plate on its western margin, and the Indian and smaller plates along its southern side in New Guinea and the Bismarck Sea area. The southern Yap Trench, the Palau Trench, and an accreting plate boundary within the Ayu Trough manifested as an axial rift valley comprise the Caroline-Philippine plate boundary. On the basis of sediment thickness and subsidence of basement away from the rift, we estimate that the Ayu Trough started to open during the Miocene. The northern section of Pacific-Caroline plate boundary coincides with the Sorol Trough which exhibits both strike-slip and extensional characteristics. The southeastern section of this boundary occurs along the Mussau Trench where Caroline plate underthrusts the Pacific plate. The section of plate boundary between the Sorol Trough and Mussau Trench is characterized by highly unusual deformational tectonics. Convergence between the Pacific and Caroline plates is apparently accommodated here by overthrusting of small slivers of sea floor towards the northeast. The intensity of deformation appears to increase southward towards the Mussau Trench. Our calculated instantaneous angular rotation vector for the Pacific-Caroline plates predicts that convergence rates increase uniformly south along the overthrust and underthrust sections of plate boundary. The transition in tectonic style from overthrusting to underthrusting occurs between 3° and 4°N. |
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