Variations in axial morphology, segmentation, and seafloor roughness along the Pacific‐Antarctic Ridge between 56°S and 66°S

Ondréas, Hélène; Aslanian, Daniel; Géli, Louis; Olivet, Jean-Louis; Briais, A.

doi:10.1029/2000jb900394

Cited by 17 publications

(11 citation statements)

References 32 publications

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“…Along the geographically remote southwestern half of the plate boundary (Fig. 31a), a dense multibeam and magnetic survey of the Pitman fracture zone (Cande et al 1995) and multibeam and magnetic data from an extensive survey of the plate boundary between 175°W and 142°W (Ondreas et al 2001) greatly increase the number and quality of the available data where it was sparse before. We also determined five spreading rates from isolated magnetic profiles of the sparsely surveyed ridge axis between the Macquarie triple junction and 180°E, four from transit tracks of the R/V Nathaniel B. Palmer (shown in Figs 9 and 40) and one from an isolated magnetic profile (AB08 in Fig.…”

Section: Data and Results: Best‐fitting And Morvel Plate Motion Estmentioning

confidence: 99%

Geologically current plate motions

DeMets¹,

Gordon

Argus

2010

Geophysical Journal International

2,234

1,664

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S U M M A R YWe describe best-fitting angular velocities and MORVEL, a new closure-enforced set of angular velocities for the geologically current motions of 25 tectonic plates that collectively occupy 97 per cent of Earth's surface. Seafloor spreading rates and fault azimuths are used to determine the motions of 19 plates bordered by mid-ocean ridges, including all the major plates. Six smaller plates with little or no connection to the mid-ocean ridges are linked to MORVEL with GPS station velocities and azimuthal data. By design, almost no kinematic information is exchanged between the geologically determined and geodetically constrained subsets of the global circuit-MORVEL thus averages motion over geological intervals for all the major plates. Plate geometry changes relative to NUVEL-1A include the incorporation of Nubia, Lwandle and Somalia plates for the former Africa plate, Capricorn, Australia and Macquarie plates for the former Australia plate, and Sur and South America plates for the former South America plate. MORVEL also includes Amur, Philippine Sea, Sundaland and Yangtze plates, making it more useful than NUVEL-1A for studies of deformation in Asia and the western Pacific. Seafloor spreading rates are estimated over the past 0.78 Myr for intermediate and fast spreading centres and since 3.16 Ma for slow and ultraslow spreading centres. Rates are adjusted downward by 0.6-2.6 mm yr −1 to compensate for the several kilometre width of magnetic reversal zones. Nearly all the NUVEL-1A angular velocities differ significantly from the MORVEL angular velocities. The many new data, revised plate geometries, and correction for outward displacement thus significantly modify our knowledge of geologically current plate motions. MORVEL indicates significantly slower 0.78-Myr-average motion across the Nazca-Antarctic and Nazca-Pacific boundaries than does NUVEL-1A, consistent with a progressive slowdown in the eastward component of Nazca plate motion since 3.16 Ma. It also indicates that motions across the Caribbean-North America and Caribbean-South America plate boundaries are twice as fast as given by NUVEL-1A. Summed, least-squares differences between angular velocities estimated from GPS and those for MORVEL, NUVEL-1 and NUVEL-1A are, respectively, 260 per cent larger for NUVEL-1 and 50 per cent larger for NUVEL-1A than for MORVEL, suggesting that MORVEL more accurately describes historically current plate motions. Significant differences between geological and GPS estimates of Nazca plate motion and Arabia-Eurasia and India-Eurasia motion are reduced but not eliminated when using MORVEL instead of NUVEL-1A, possibly indicating that changes have occurred in those plate motions since 3.16 Ma. The MORVEL and GPS estimates of Pacific-North America plate motion in western North America differ by only 2.6 ± 1.7 mm yr −1 , ≈25 per cent smaller than for NUVEL-1A. The remaining difference for this plate pair, assuming there are no unrecognized systematic errors and no measurable change in Pacific-North America motion ...

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Section: Data and Results: Best‐fitting And Morvel Plate Motion Estmentioning

confidence: 99%

Geologically current plate motions

DeMets¹,

Gordon

Argus

2010

Geophysical Journal International

2,234

1,664

View full text Add to dashboard Cite

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“…As revealed by satellite gravity data and detailed swath bathymetry, the axial morphology of the Pacific Antarctic Ridge between 175°W in this region changes from a rift valley in the western part (from 175°W to ∼157°W) to an axial dome in the eastern part (157°W and 145°W) of the section, reflecting the along‐axis increase in spreading rate from slow to fast [ Géli et al , 1997; Ondréas et al , 2001]. As is typical for slow spreading centers, the western part of the section is characterized by a rough sea floor with many well‐marked fracture zones.…”

Section: Resultsmentioning

confidence: 99%

Mantle helium reveals Southern Ocean hydrothermal venting

Winckler¹,

Newton

Schlosser³

et al. 2010

Geophysical Research Letters

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Hydrothermal venting along the global mid‐ocean ridge system plays a major role in cycling elements and energy between the Earth's interior and surface. We use the distribution of helium isotopes along an oceanic transect at 67°S to identify previously unobserved hydrothermal activity in the Pacific sector of the Southern Ocean. Combining the geochemical information provided by the helium isotope anomaly with independent hydrographic information from the Southern Ocean, we trace the source of the hydrothermal input to the Pacific Antarctic Ridge south of 55°S, one of the major global mid‐ocean ridge systems, which has until now been a ‘blank spot’ on the global map of hydrothermal venting. We identify three complete ridge segments, a portion of a fourth segment and two isolated locations on the Pacific Antarctic Ridge between 145°W and 175°W (representing ∼540 km of ridge in total) as the potential source of the newly observed plume.

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“…The off‐axis lineations appear near 70 Ma on the flanks of the Pacific‐Antarctic Ridge (PAR, Figure 7). The lineations then disappear, near 30 Ma just south of Udintsev FZ, and at progressively younger ages toward the south, resulting in a V‐shaped boundary between seafloor affected by small‐scale gravity lineations and smooth seafloor [ Sahabi et al , 1996; Géli et al , 1997; Ondréas et al , 2001].…”

Section: Analysis Of the Segmentationmentioning

confidence: 99%

Temporal variations of the segmentation of slow to intermediate spreading mid‐ocean ridges 1. Synoptic observations based on satellite altimetry data

Briais

2002

J. Geophys. Res.

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[1] The high-resolution geoid and gravity maps derived from ERS-1 and Geosat satellite geodetic missions reveal a set of small-scale lineations on the flanks of slow to intermediate spreading midocean ridges. Assuming that these lineations reflect the variations in crustal structure induced by mid-ocean ridge axial discontinuities, we use them to investigate how the discontinuities, and the segments they bound, appear, migrate, and disappear. We provide a synoptic description of the main characteristics of the crustal structure variations, as well as their evolution in time, over the flanks of the Mid-Atlantic, Indian, and Pacific-Antarctic Ridges. The second-order segment length does not appear to vary with the spreading rate for the slow to intermediate spreading ridges investigated here. The amplitude of the gravity signal associated with off-axis discontinuity traces increases with the obliquity of the ridge to spreading and decreases with spreading rate and with the proximity of a ridge section to a hot spot. The patterns of the gravity lineations appear to be very homogeneous over 500-to 1000-km-large corridors bounded by large fracture zones. Far from hot spots, corridors are characterized either by segments bounded by discontinuities migrating back and forth along the axis, implying a lifetime of 10 -30 Myr for the segments, or by segments and discontinuities very stable in space and time, surviving for 40 -50 Myr. Closer to hot spots, the segmentation is affected in two ways. First, segments tend to migrate along axis away from hot spots, or toward cold spots. Second, asymmetric spreading tends to keep sections of ridges closer to hot spots than normal spreading would. These observations support the hypothesis that ridge segmentation and its evolution are controlled by mantle dynamics. Our analysis provides observational constraints for further models of crustal production along ridges, which are presented in the companion paper by Rabinowicz and Briais [2002].

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Variations in axial morphology, segmentation, and seafloor roughness along the Pacific‐Antarctic Ridge between 56°S and 66°S

Cited by 17 publications

References 32 publications

Geologically current plate motions

Geologically current plate motions

Mantle helium reveals Southern Ocean hydrothermal venting

Temporal variations of the segmentation of slow to intermediate spreading mid‐ocean ridges 1. Synoptic observations based on satellite altimetry data

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