Global and Regional Assessments of Paleosecular Variation Activity Over the Past 100 ka

Abstract

We present a global compilation of paleomagnetic data spanning the past 100 ka. Sediment data comprise 61,687 declinations, 70,936 inclinations, and 69,596 relative paleointensities. Many sites are located in the northern Atlantic and western Pacific, with approximately twice as many data from the Northern Hemisphere as from the Southern Hemisphere. The 14,954 volcanic and archeomagnetic data are sparse, especially in the Southern Hemisphere. Directional and intensity information are aggregated under the paleosecular variation (PSV) index to assess occurrence of excursions over the past 100 ka. The Laschamp excursion (∼41 ka) is clearly defined across globally distributed sediment records with an average duration of 1,300 years. Regional stacks obtained using bootstrap resampling show a more pronounced Laschamp excursion in the Northern Hemisphere than in the Southern, and in the Atlantic Hemisphere compared with the Pacific. No anomalous indices occurred around the Mono Lake excursion or other periods in the bootstrap curves. This may result from low sedimentation rates, discrepancies in age scales, large age errors, and/or the lack of global character of any transitional events. These data and associated new uncertainty estimates for the sediment records provide a good foundation for global, time‐dependent, spherical harmonic field modeling for the past 100 ka.

One Hundred Thousand Years of Geomagnetic Field Evolution

“…The standard deviation of the index over time is a measure for field variability in the time interval and is called PSV activity. The PSV index can be determined for data records, empirical geomagnetic field models or numerical dynamo simulations, and can be used to compare field variability regionally, globally, and in time (Panovska et al, ).…”

“…(a) Distribution of the number of studies by year of publication (one year bins). Different colors represent sediment studies from the 100 ka data compilation by Panovska, Constable, and Brown (), and archeomagnetic and volcanic data from the GEOMAGIA50.v3 (Brown, Donadini, Korte, et al, ) and PSV10 (Cromwell et al, ) databases. Distributions of studied regions in publications from the GEOMAGIA50.v3 and PSV10 databases (b) and the sediment data compilation (c).…”

“…Therefore, only records that have previously been used in such syntheses are considered here, and some more recently published records are not included. The geographic distribution of the GEOMAGIA50.v3 (Brown, Donadini, Korte, et al, ) and PSV10 (Cromwell et al, ) databases and of the sediment data compilation of (Panovska, Constable, & Brown, ) are given in Figures b and c. The European region is covered best by volcanic and archeomagnetic data (60%), followed by Asia and North America each with 13%.…”

“…The number of data points in the individual records varies, influencing the temporal resolution or smoothing time of the time series. (Panovska, Constable, & Brown, ) show that more than 70% of the records have a temporal resolution better than 1 kyr, but a few low‐resolution records have smoothing times of up to 6 kyr. Over the whole time interval, the highest numbers of directional data are found in the Holocene period and during the Laschamp excursion (∼41 ka BP).…”

“…(a) Spatial distribution of sediments and volcanic data in the data set of Panovska, Constable, and Brown (). Maps represent probability distribution functions on a log scale.…”