PSVM: A Global Database for the Miocene Indicating Elevated Paleosecular Variation Relative to the Last 10 Myrs
PSVM: A Global Database for the Miocene Indicating Elevated Paleosecular Variation Relative to the Last 10 Myrs
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DOI：
10.1029/2022gc010480
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发表时间：
2022-08
期刊：
影响因子：
3.7
通讯作者：
Y. A. Engbers;R. Bono;A. Biggin
中科院分区：
文献类型：
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作者：
Y. A. Engbers;R. Bono;A. Biggin
古长期变化的统计研究（PSV）被用来推断地磁场的结构和行为。该研究建立了一个新的数据库——中新世古长期变化（PSVM），该数据库收集了来自44个不同地区的1454个地点的中新世（5.3-23 Ma）的高质量定向数据。利用该数据库以模型G为基础，利用不同选择标准的二次型模型对古世俗变化的纬度依赖关系进行建模。我们拟合的纬度不变PSV模型参数（模型G a）为15.6°，纬度相关PSV项（模型G b）为0.23。纬度不变项大大高于过去10兆尔或任何其他研究年龄的观测值。我们还提出了一个新的时间平均场随机模型BB - M22，该模型使用协变巨高斯过程（GGP），该过程使用来自PSVM， PINT和类地地球动力学数值模拟的数据进行约束。相对于之前的GGP模型，BB‐M22提高了对PSVM数据的拟合，因为它再现了中新世观测到的更高的虚拟地磁极（VGP）色散。我们的研究结果表明，中新世的磁场变化更大，地球动力比过去10万年更活跃，这可能与核心-地幔热流升高有关。我们的研究结果表明，时间瞬时场的平均轴向偶极子优势比最近的时间要低。然而，我们注意到，倾斜异常估计表明，不能排除中新世时间平均场类似于地心轴向偶极子。
Statistical studies of paleosecular variation (PSV) are used to infer the structure and behavior of the geomagnetic field. This study presents a new database, paleosecular variation of the Miocene (PSVM), of high‐quality directional data from the Miocene Epoch (5.3–23 Ma), compiled from 1,454 sites from 44 different localities. This database is used to model the latitude dependence of paleosecular variation with varying selection criteria using a quadratic form based on Model G. Our fitted model parameter for latitude‐invariant PSV (Model G a) is 15.6° and the latitude dependent PSV term (Model G b) is 0.23. The latitude invariant term is substantially higher than previously observed for the past 10 Myrs or any other studied ages. We also present a new stochastic model of the time‐average field, BB‐M22, using a covariant giant Gaussian process (GGP) which is constrained using data from PSVM, PINT and Earth‐like geodynamo numerical simulations. BB‐M22 improves the fit to PSVM data relative to prior GGP models, as it reproduces the higher virtual geomagnetic pole (VGP) dispersion observed during the Miocene. Our findings suggest a more variable magnetic field and more active geodynamo in the Miocene Epoch than the past 10 Myrs, perhaps linked to elevated core‐mantle heat flow. Our results suggest that the average axial dipole dominance of the time‐instantaneous field was lower than in more recent times. We note however, that the inclination anomaly estimates, suggest that it cannot be ruled out that the Miocene time averaged field resembles a geocentric axial dipole.