The Manila Trench-West Taiwan Foldbelt: A Flipped Subduction Zone

Author : R. W. Murphy
Publication : Bulletin of the Geological Society of Malaysia
Page : 27-42
Volume Number : 6
Year : 1973

Bulletin of the Geological Society of Malaysia, Volume 6, Jul, 1973, pp. 27 – 42

The Manila Trench – West Taiwan Foldbelt: A Flipped Subduction Zone


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Abstract: The Manila Trench-West Taiwan Foldbelt is an anomalous west-facing island arc segment of the western Pacific. It is postulated to be a young, east-dipping subduction zone which flipped in Pliocene time from a former west-dipping position on the east side of Luzon and Taiwan, where it probably formed a continuous subduction zone with the Ryukyu and Philippine Trenches.

The eastward dip of the Manila Trench is supported by the published work of Ludwig, Hays, and Ewing. Its continuation into western Taiwan is inferred from topographic alignments, published cross sections, and the probable eastward dip of the seismic focal plane. The hypothesis of flipping is introduced to explain the geologic characteristics of the structural belts of Taiwan and the apparent offset between the northern end of the Philippine Trench and the southern end of the Manila Trench. The time of flipping is inferred from tectonic events dated by surface geological means.

The northern termination of the subduction zone is a trench-to-trench transform between northernmost Taiwan and Yonaguni Island of the southwest Ryukyu Islands. The southern end is also a trench-to-trench transform expressed at the surface by left-lateral wrench faulting west of Atimonan, at the northern end of the Bondoc Peninsula.

The Central Taiwan Range is considered to be a fossil Upper Cretaceous subduction zone containing oceanic sediments of Late Paleozoic to Cretaceous? age. It is flanked on the west by a Paleogene continental rise flysch prism, deposited when subduction was dormant or had shifted to the east, and on the east by a Neogene andesitic island arc complex, which prior to flipping overlooked a west-dipping subduction zone on the Pacific side.

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