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Underthrusting at the Hjort Trench, Australian-Pacific plate boundary: incipient subduction?
Citation
Meckel, TA and Coffin, MF and Mosher, S and Symonds, P and Bernardel, G and Mann, P, Underthrusting at the Hjort Trench, Australian-Pacific plate boundary: incipient subduction?, Geochemistry Geophysics Geosystems, 4 EJ ISSN 1525-2027 (2003) [Refereed Article]
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Copyright Statement
Copyright 2003 by the American Geophysical Union
Abstract
[1] The southernmost portion of the Macquarie Ridge Complex (MRC) comprises the Hjort Ridge,
Trench, and Plateau, the topographic expression of the Australian-Pacific plate boundary south of New
Zealand. On the basis of marine geophysical (swath bathymetry/reflectivity, seismic reflection, gravity,
magnetic) data, teleseismic data, and gravity modeling, we argue that the Australian plate is actively
underthrusting the Pacific plate along the Hjort Trench, but self-sustaining subduction does not yet
appear to have commenced. We interpret a crustal discontinuity in the Trench as a shallowly dipping
thrust splay off a sub-vertical transform fault in the crest of the Hjort Ridge (Hjort Fault). The Hjort
Fault separates oceanic crust generated at the Southeast Indian Ridge (SEIR crust), located to the south,
from oceanic crust generated at the extinct Australian-Pacific spreading center located to the north
(MRC crust). Oblique convergence on the transform has initiated a significant plate boundary
decollement in the Trench, but our estimate of 50 km of underthrusting does not support the existence
of an eastwardly dipping Australian slab below 20 km depth. For the length of the Hjort Ridge and
Trench system, oblique convergence is partitioned between the decollement in the Trench and the Hjort
Fault. South of 57.5S, the trench decollement accommodates thrusting. North of 57.5S, the boundaryparallel
component of convergence becomes dominant, the Trench gradually shallows, and the trench decollement evolves into a low-angle, oblique-slip fault. The trench decollement and strike-slip system
in the Hjort Ridge are structural boundaries that contain tectonic slivers of inferred SEIR crust of the western flank of the Hjort Ridge that currently belong to neither the Australian nor the Pacific plates.
Item Details
Item Type: | Refereed Article |
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Keywords: | Subduction initiation; Hjort Trench; Macquarie Ridge Complex; marine tectonics; strain partitioning; oblique |
Research Division: | Earth Sciences |
Research Group: | Geology |
Research Field: | Marine geoscience |
Objective Division: | Expanding Knowledge |
Objective Group: | Expanding knowledge |
Objective Field: | Expanding knowledge in the earth sciences |
UTAS Author: | Coffin, MF (Professor Mike Coffin) |
ID Code: | 73808 |
Year Published: | 2003 |
Web of Science® Times Cited: | 28 |
Deposited By: | Research Division |
Deposited On: | 2011-10-26 |
Last Modified: | 2011-11-09 |
Downloads: | 0 |
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