Publication Date:
2019
Description:
Abstract
Statistical analysis of geomagnetic paleosecular variation (PSV) and time averaged field (TAF) has been largely based on global compilations of paleomagnetic data from lava flows. These show different trends in the averaged inclination anomaly (ΔI) between the two hemispheres, with small positive (〈2°) anomalies in mid‐southern latitudes and large negative (〉‐5°) anomalies in mid‐northern latitudes. To inspect the large ΔI between 20°N‐40°N we augment the global data with a new paleomagnetic dataset from the Golan‐Heights (GH), a Plio‐Pleistocene volcanic plateau in northeast Israel, located at 32°N‐33°N. The GH dataset consists of 91 lava flows sites: 40 sites obtained in the 1990s and 51 obtained in this study. The chronology of the flows is constrained by 57 40Ar/39Ar ages: 39 from previous studies and 18 from this study, which together cover most of the GH plateau. We show that the 1990s dataset might be affected by block rotations and does not fully sample PSV. The Plio‐Pleistocene pole (86.3°N, 120.8°E, N=44, k=25, α95=4.4°), calculated after applying selection criteria with Fisher precision parameter (k) ≥ 100 and number of specimens per site (n) ≥ 5 is consistent with a geocentric axial dipole field and shows smaller inclination anomaly (ΔI=‐0.4°) than predicted by global compilations and PSV models. Re‐examination of the inclination anomaly in the global compilation using different calculation methods and selection criteria suggests that inclination anomaly values are affected by: (1) inclusion of poor quality data, (2) averaging data by latitude bins and (3) the way the inclination anomaly is calculated.
Electronic ISSN:
1525-2027
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
