The seafloor spreading rate dependence of the anomalous skewness of marine magnetic anomalies

Roest, W. R.; Arkani‐Hamed, J.; Verhoef, J.

doi:10.1111/j.1365-246x.1992.tb00123.x

Cited by 35 publications

(41 citation statements)

References 47 publications

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“…Our anomalous skewness estimate is consistent with the trend of anomalous skewness versus spreading rate found by Roest et al (1992), which is unsurprising as their results included preliminary results from our work (Fig. 18).…”

Section: Dependence Of Anomalous Skewness On Spreading Ratesupporting

confidence: 89%

“…Anomalous skewness depends on spreading rate (Cande 1976(Cande , 1978Arkani-Hamed 1988;Roest et al 1992). Our anomalous skewness estimate is consistent with the trend of anomalous skewness versus spreading rate found by Roest et al (1992), which is unsurprising as their results included preliminary results from our work (Fig.…”

Section: Dependence Of Anomalous Skewness On Spreading Ratementioning

confidence: 99%

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A 57 Ma Pacific plate palaeomagnetic pole determined from a skewness analysis of crossings of marine magnetic anomaly 25r

Petronotis

Gordon

Acton

1994

Geophysical Journal International

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An increase in the accuracy and age resolution of the apparent polar wander path of the Pacific plate could be important for testing reconstructions that relate the motion of Pacific basin plates to other plates, for testing if hotspots in different ocean basins are stationary relative to one another, and for estimating the motion of hotspots relative to the spin axis. With these goals in mind, herein we investigate how accurately a palaeomagnetic pole can be estimated from skewness analysis of many crossings of a single magnetic anomaly on the Pacific plate. Apparent effective remanent inclinations of the sea-floor magnetization were estimated from the skewnesses of 132 useful (out of 149 total) crossings of anomaly 25r (56.5-57.8 Ma) distributed over a distance of more than 11 OOO km across the Pacific plate. These estimates were inverted to obtain a best-fitting palaeomagnetic pole latitude, pole longitude, and anomalous skewness for this single reversed-polarity chron. The best-fitting model gives a pole of 78.2"N, 4.8"E with a 95 per cent confidence ellipse having a 6.4" major semi-axis oriented 93" clockwise of north and a 4.1" minor semi-axis; anomalous skewness is 16.2" f 4.6" (95 per cent confidence limits). We also investigated the effect of the dependence of anomalous skewness on spreading rate by correcting our data using an empirical model. The pole obtained from the inversion of this alternative data set lies a statistically insignificant 0.6" from the pole obtained using no correction. That a pole with usefully compact confidence limits and a narrowly resolved, precisely estimated age can be so determined suggests that an accurate apparent polar wander path with a fine-age resolution can be determined for the Pacific plate by applying the same approach to the shapes of other marine magnetic anomaliks.Comparison of our chron 25r pole with other Pacific palaeomagnetic and palaeoequatorial sediment facies data indicates that the Pacific plate remained nearly stationary relative to the spin axis during the Eocene (-0.05" Myr-' f 0.28" Myr-I), but probably moved rapidly northward during the Paleocene (0.83" Myr-' f 0.46" Myr-I). Comparison of these data to latitudes of dated volcanic edifices along the Hawaiian-Emperor chain indicates that the Hawaiian hotspot drifted southward by 10.2" f 3.4" (95 per cent confidence limits) since 57 Ma, but only by 1.7" f 1.9" since 39 Ma, which gives a southward displacement of 8.5" f 3.9" (95 per cent confidence limits) between 57 and 39Ma, corresponding to a rate of southward motion of 52 f 24 mm yr-'. Incorporation of realistic uncertainties of volcano ages would increase these uncertainties considerably, however. We also examined the distance between the crossings of anomalies 25 and 27 on all the profiles we analysed; along the palaeo-Pacific-Farallon boundary these distances are inconsistent with the joint hypotheses of symmetric spreading and single Pacific and Farallon plates between 62 and 56Ma, indicating that the evidence for a single Pacific plate in early...

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Section: Dependence Of Anomalous Skewness On Spreading Ratesupporting

confidence: 89%

Section: Dependence Of Anomalous Skewness On Spreading Ratementioning

confidence: 99%

A 57 Ma Pacific plate palaeomagnetic pole determined from a skewness analysis of crossings of marine magnetic anomaly 25r

Petronotis

Gordon

Acton

1994

Geophysical Journal International

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“…Reduction of spreading rate to very low values ( < 1 0 k m Ma -1) has also been observed to give rise to areas of particularly rough basement topography. Examples are seen in the Weddell Sea itself, on crust dated at C29 to C21 at Princeton University on July 17, 2015 http://sp.lyellcollection.org/ Downloaded from (Livermore & Woollett 1993), and in the Labrador Sea after C21 (Roest & Srivastava 1989). Furthermore, the anomalous skewness of magnetic anomalies has been found to increase as spreading rate decreases (Roest et al 1992).…”

Section: Discussionmentioning

confidence: 97%

Mesozoic seafloor spreading in the southern Weddell Sea

Livermore

Hunter

1996

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A re-evaluation of Weddell Sea magnetic anomaly data, in the light of satellite gravity maps, provides important constraints on plate kinematics prior to chron C34 (83Ma). Although M-series anomalies are difficult to identify, the evidence favours younger ages than previously suggested, based on the assumption that these anomalies formed at the South America-Antarctica plate boundary. Geosat-derived free-air gravity maps show a distinct anomaly, 'Anomaly-T', associated with the southern termination of a herring-bone pattern of flow lines. The associated magnetic anomaly has been identified previously as anomaly M20, on the basis of a model of very slow spreading, but is interpreted here as an edge-effect, associated with an abrupt decline in spreading rate which occurred between M4 (126 Ma) and M0 (118 Ma), and which induced the fine segmentation pattern to the north. Although anomalies are present to the south of Anomaly-T, they are of reduced amplitude, and are difficult to correlate over distances of more than c. 100km. Nevertheless, they appear to strike approximately W-E, sub-parallel to the younger anomalies to the north, and show a resemblance to anomalies M4-M12, modelled at a rate of 15 km Ma -1.Flow-line modelling, based on published rotations for the Southwest Indian Ridge and southern Mid-Atlantic Ridge, gives a reasonable fit to the observed trends of Weddell Sea gravity ridges. Two alternative models for the M-series reconstruction of Africa and Antarctica are employed, corresponding to the two M2 fits suggested by Bergh. Although it is not possible to reject either of the models, the tighter fit of the two gives slightly better agreement with Weddell Sea trends. In both models, a drop in rates occurs at M0 time.Anomalies farther south correspond with previously identified features, such as the Orion, Explora and Andenes anomalies, and the Polarstern Bank, all characterized by magnetic anomaly highs, attributed to excess volcanism during early break-up.

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“…Since the two actual measurements at spreading rates of 7.5 and 22 km Myr-I. (Roest et al 1992) are above the upper bound of predicted anomalous skewness, a magnetic uppermost mantle is required to account for the observed anomalous skewness.…”

Section: Magnetization Model Of the Oceanic Lithospherementioning

confidence: 99%

Spreading-rate-dependent magnetization of the oceanic lithosphere inferred from the anomalous skewness of marine magnetic anomalies

Dyment

Arkani‐Hamed

1995

Geophysical Journal International

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S U M M A R YThe anomalous skewness of marine magnetic anomalies decreases with increasing spreading rate and becomes negligible above a spreading rate of about 50 km Myr-I. Previous magnetization models of the oceanic lithosphere fail to explain this observation. We propose a new model in which the magnetic structure of the oceanic lithosphere is dependent on spreading rate. Anomalous skewness measurements for anomalies 33 reversed and 25 reversed at various spreading rates are in agreement with a magnetization model in which layer 3 and the uppermost mantle bear a similar saturation magnetization, and the ratio of layer 3 over layer 2A saturation magnetizations varies linearly from about 0.4 at a spreading rate of 10kmMyr-' to about 0 at 55kmMyr-I. For spreading rates higher than 55 km Myr-', layer 3 and uppermost mantle magnetizations are negligible. Recent advances concerning accretionary processes at mid-ocean ridges suggest that the combined effect of variations with spreading rate of magma fractionation, alteration of layer 2A, and serpentinization of layer 3 and the uppermost mantle may account for the proposed variation of magnetization with spreading rate.

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The seafloor spreading rate dependence of the anomalous skewness of marine magnetic anomalies

Cited by 35 publications

References 47 publications

A 57 Ma Pacific plate palaeomagnetic pole determined from a skewness analysis of crossings of marine magnetic anomaly 25r

A 57 Ma Pacific plate palaeomagnetic pole determined from a skewness analysis of crossings of marine magnetic anomaly 25r

Mesozoic seafloor spreading in the southern Weddell Sea

Spreading-rate-dependent magnetization of the oceanic lithosphere inferred from the anomalous skewness of marine magnetic anomalies

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