A Maastrichtian palaeomagnetic pole for the Pacific plate from a skewness analysis of marine magnetic anomaly 32
A Maastrichtian palaeomagnetic pole for the Pacific plate from a skewness analysis of marine magnetic anomaly 32
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通过海洋磁异常的偏度分析得出太平洋板块的马斯特里赫特古磁极 32
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发表时间：
1999
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通讯作者：
R. Gordon
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作者：
K. Petronotis;R. Gordon
摘要 对太平洋板块海洋磁异常 32（72.1‐73.3 Ma）的不对称性（偏度）进行了分析，以估计新的古地磁极。海底磁化强度的视有效剩磁倾角是根据分布在整个太平洋板块、跨越约 12 000 公里大圆距离的异常 32 的 108 个交叉点的偏斜估计来计算的。对数据进行反演，得到位于北纬 72.1°、东经 26.8° 的古地磁极，其置信度为 95% 的椭圆具有 4.0° 的长半轴（朝北顺时针方向 98°）和 1.8° 的短半轴；异常偏度为14.2°±3.7°。通过两个经验模型研究了异常偏度对铺展率的可能依赖性，发现在相关铺展半率范围（~25 至~90 mm yr'1）上，对我们的古极点分析的影响可以忽略不计。新极点与同时代古纬度和古赤道数据表明的太平洋板块向北运动一致，但与同时期海山极点明显不同，并且位于其东北部。我们将这种差异归因于海山极点的未建模误差，主要是赤纬。与根据夏威夷-皇帝海山链沿线的已测年火山推断出的向北运动进行比较表明，自 73 Ma 以来夏威夷热点向南运动了 13°。当用太平洋板块相对于太平洋热点重建极点时，它与极点相对于印度-大西洋热点的位置存在14°‐18°的偏差。这有几种可能的解释，包括一个或多个古地磁极的偏差、太平洋和印度-大西洋热点之间的运动以及板块重建相对于热点的误差。
SUMMARY The asymmetry (skewness) of marine magnetic anomaly 32 (72.1‐73.3 Ma) on the Pacific plate has been analysed in order to estimate a new palaeomagnetic pole. Apparent eVective remanent inclinations of the seafloor magnetization were calculated from skewness estimates of 108 crossings of anomaly 32 distributed over the entire Pacific plate and spanning a great-circle distance of ~12 000 km. The data were inverted to obtain a palaeomagnetic pole at 72.1°N, 26.8°E with a 95 per cent confidence ellipse having a 4.0° major semi-axis oriented 98° clockwise of north and a 1.8° minor semi-axis; the anomalous skewness is 14.2°±3.7°. The possible dependence of anomalous skewness on spreading rate was investigated with two empirical models and found to have a negligible eVect on our palaeopole analysis over the range of relevant spreading half-rates, ~25 to ~90 mm yr’1. The new pole is consistent with the northward motion for the Pacific plate indicated by coeval palaeocolatitude and palaeoequatorial data, but diVers significantly from, and lies to the northeast of, coeval seamount poles. We attribute the diVerence to unmodelled errors in the seamount poles, mainly in the declinations. Comparison with the northward motion inferred from dated volcanoes along the Hawaiian‐Emperor seamount chain indicates 13° of southward motion of the Hawaiian hotspot since 73 Ma. When the pole is reconstructed with the Pacific plate relative to the Pacific hotspots, it diVers by 14°‐18° from the position of the pole relative to the Indo‐Atlantic hotspots. This has several possible explanations including bias in one or more of the palaeomagnetic poles, motion between the Pacific and Indo‐Atlantic hotspots, and errors in plate reconstructions relative to the hotspots.