Sea-floor spreading in the easternmost Indian Ocean reveals cyclicity in ocean crust accretion (0–36 Ma)

Lodolo, Emanuele; Schreider, A. A.; Coren, F.

doi:10.1016/0025-3227(96)00043-6

Cited by 4 publications

(5 citation statements)

References 15 publications

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“…Away from the plate boundary zone, we employed an oceanic crustal section ∼7 km thick, consisting of ∼2 km of upper crust and ∼5 km of lower crust. These thicknesses are appropriate for crust of the ages implied by the available magnetic anomalies [ White et al , 1992; Wood et al , 1996] and estimated spreading rates [ Bown and White , 1994; Lodolo et al , 1996]. The models emphasize changes in subsurface geometry of the three layers, keeping layer densities constant, rather than introducing intralayer density variability.…”

Section: Gravity Modeling Of Integrated Crustal Structurementioning

confidence: 99%

Underthrusting at the Hjort Trench, Australian‐Pacific plate boundary: Incipient subduction?

Meckel

Coffin

Mosher

et al. 2003

Geochem Geophys Geosyst

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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 57.5°S, the trench decollement accommodates thrusting. North of 57.5°S, the boundary‐parallel 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.

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Section: Gravity Modeling Of Integrated Crustal Structurementioning

confidence: 99%

Underthrusting at the Hjort Trench, Australian‐Pacific plate boundary: Incipient subduction?

Meckel

Coffin

Mosher

et al. 2003

Geochem Geophys Geosyst

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“…Analyses of sparse underway geophysical profiles crossing the westernmost part of the Pacific‐Antarctic plate boundary, combined with satellite‐derived maps, have revealed a sequence of closely spaced, short ridge segments, offset by NNW‐SSE trending transform faults [ Cande et al ., ; Lodolo and Coren , ]. The two main lineaments that border to the northeast and to the southwest the array of the short ridge segments have been interpreted as boundaries of a young oceanic area, based on the identification of marine magnetic anomalies [ Lodolo et al ., ; Lodolo and Coren , ]. This area developed in the Late Miocene as a response to a major change in the Pacific‐Antarctic plate motion, which caused extension along an old NW‐SE trending fracture zone (the Emerald Fracture Zone) that originally distributed the relative motion between the two plates [ Lodolo and Coren , ].…”

Section: Regional Backgroundmentioning

confidence: 99%

“…From 7 to 10 Ma, the computed velocities used to produce the synthetic model are, on average, of 4.2 cm/yr for both flanks of the ridge. The spreading velocity distribution shows that the process of ocean crust accretion was not uniform, with a general trend of decreasing spreading rates versus time [ Lodolo et al ., ]. The weighted average of the spreading rates calculated along the eastern SEIR ridge gives a value of 3.8 cm/yr for the period from 0 to 6 Ma.…”

Section: Geophysical Datamentioning

confidence: 99%

“…[] and those located to the southwest have been taken from Lodolo et al . []. Light gray areas indicate the presence of seamounts and/or mantle plume tracks, as individuated from bathymetric and multichannel seismic reflection profiles.…”

Section: The Western Pacific‐antarctic Plate Boundarymentioning

confidence: 99%

“…There are striking similarities between the seismic character of these oceanic features and that of the transverse ridges of several other Pacific fracture zones, like the well-studied Clipperton Fracture Zone [Pockalny, 1997] and the Shackleton Fracture Zone [Livermore et al, 2004;Geletti et al, 2005], where the active trace is marked by a Figure 1), with the distribution of the identified magnetic anomalies (numbered dotted lines). Anomalies located to the northeast of the "leaky transform system" have been taken from and Croon et al [2008] and those located to the southwest have been taken from Lodolo et al [1996]. Light gray areas indicate the presence of seamounts and/or mantle plume tracks, as individuated from bathymetric and multichannel seismic reflection profiles.…”

Section: Geophysical Datamentioning

confidence: 99%

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How do long‐offset oceanic transforms adapt to plate motion changes? The example of the Western Pacific‐Antarctic plate boundary

2013

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Oceanic transform faults respond to changes in the direction of relative plate motion. Studies have shown that short‐offset transforms generally adjust with slight bends near the ridge axis, while long‐offset ones have a remarkably different behavior. The western Pacific‐Antarctic plate boundary highlights these differences. A set of previously unpublished seismic profiles, in combination with magnetic anomaly identifications, shows how across a former, ~1250 km long transform (the Emerald Fracture Zone), plate motion changes have produced a complex geometric readjustment. Three distinct sections are recognized along this plate boundary: an eastern section, characterized by parallel, multiple fault strand lineaments; a central section, shallower than the rest of the ridge system, overprinted by a mantle plume track; and a western section, organized in a cascade of short spreading axes/transform lineaments. This configuration was produced by changes that occurred since 30 Ma in the Australia‐Pacific relative plate motion, combined with a gradual clockwise change in Pacific‐Antarctic plate motion. These events caused extension along the former Emerald Fracture Zone, originally linking the Pacific‐Antarctic spreading ridge system with the Southeast Indian ridge. Then an intra‐transform propagating ridge started to develop in response to a ~6 Ma change in the Pacific‐Antarctic spreading direction. The close proximity of the Euler poles of rotation amplified the effects of the geometric readjustments that occurred along the transform system. This analysis shows that when a long‐offset transform older than 20 Ma is pulled apart by changes in spreading velocity vectors, it responds with the development of multiple discrete, parallel fault strands, whereas in younger lithosphere, locally modified by thermal anisotropies, tensional stresses generate an array of spreading axes offset by closely spaced transforms.

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A Late Miocene plate boundary reorganization along the westernmost Pacific-Antarctic ridge

Lodolo

Coren

1997

Tectonophysics

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Sea-floor spreading in the easternmost Indian Ocean reveals cyclicity in ocean crust accretion (0–36 Ma)

Cited by 4 publications

References 15 publications

Underthrusting at the Hjort Trench, Australian‐Pacific plate boundary: Incipient subduction?

Underthrusting at the Hjort Trench, Australian‐Pacific plate boundary: Incipient subduction?

How do long‐offset oceanic transforms adapt to plate motion changes? The example of the Western Pacific‐Antarctic plate boundary

A Late Miocene plate boundary reorganization along the westernmost Pacific-Antarctic ridge

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