Picking, choosing and re-evaluating: Developing a deglacial palaeomagnetic secular variation (PSV) master curve for Fennoscandia.

Abstract:

Decades of extensive palaeomagnetic research have resulted in an abundance of late-Pleistocene and Holocene palaeomagnetic secular variation (PSV) datasets. The accuracy of these datasets is dependent not only upon the quality of the PSV data, but also on the geochronological methods used for age determination of the PSV data. We showcase our recently published work (Lougheed et al., 2014), whereby we demonstrate the potential of using existing datasets that have been published in the past 35 years, whereby we evaluate the datasets and update the geochronologies to reflect improved knowledge of dating techniques. Specifically, we have developed a Fennoscandia region PSV master curve for the 14-11 ka period, to extend the existing “Fennostack” Holocene PSV master curve (Snowball et al., 2007). The 14-11 ka period in Fennoscandia was dominated by the retreat of the Fennoscandian ice sheet, and it was necessary for us to use fragmented datasets from a handful of locations that were ice-free early during the deglacial period. We updated the geochronologies of the datasets to reflect the latest understanding regarding ¹⁴C dating and pollen chronozones. We selected the updated datasets with the most robust geochronology and high-quality PSV data to construct our deglacial PSV master curve. The datasets in the resulting deglacial master curve display similar PSV trends, suggesting a regional PSV signal in Fennoscandia.

It can be concluded that, when reconstructing temporal PSV trends for large regions, consideration of the quality of both the geochronological control and the PSV data is very important. This conclusion is especially relevant for modellers who gather published PSV datasets for inclusion in their data-driven geomagnetic field models. Finally, we briefly speculate that a cyclicity seen in inclination data for Fennoscandia for the past 14 ka may be related to cyclicities previously seen in some data-driven Holocene geomagnetic field models, possibly representing an inherent feature of the geodynamo.