Summary Palaeomagnetic field intensity measurements, derived from rocks with ages that span geological time, provide a crucial constraint on the evolution of Earth’s deep interior and its magnetic environment. The palaeointensity database PINT has been updated to version v.8.0.0 and includes palaeointensity site-mean records spanning an interval from 50 ka to 4.2 Ga, compiling efforts from the palaeomagnetic community spanning from 1959 to the end of 2019. Nearly all site-mean palaeointensity records have been assessed using the qualitative reliability of palaeointensity (Quality of Palaeointensity, QPI) framework. This updated database brings together and harmonizes prior QPI and PINT compilation efforts into a unified database referred to as the PINT database, incorporating recent efforts since 2014 to assess QPI. The spatio-temporal distribution of the PINT database is analyzed, revealing substantial biases towards young records (from the Brunhes chron) in the Northern hemisphere, and intervals with little to no palaeointensity data with a duration of 10s to 100s of millions of years in the Paleozoic and Precambrian. General QPI compliance is characterized for the PINT database, which shows that the median QPI scores range from 2 to 3 (out of a total possible score of 10), with a positive trend towards increasing QPI scores in studies published after the year 2000. This illustrates an increasing community awareness of what is required to establish confidence in palaeointensity data and an increasing robustness of the large scale interpretations that can be made with these data. We additionally present a description of the long-term average dipole field strength with descriptive statistics for distinct intervals of Earth history.
The geomagnetic field exists as a consequence of a dynamic system and shows variations across a range of timescales (Johnson & McFadden, 2015). Long-term behavior is often described in terms of the intensity, reversal rate, morphology, and stability of the field. As all of these features are a result of the geodynamo, it follows that their variations should be intrinsically linked and that relationships may exist between them (
<p>Palaeomagnetic field behaviour within the Triassic is relatively poorly documented in comparison with other periods from across the last ca 250 Ma. Developing a more complete understanding of the Triassic field has important implications for discussion surrounding the Mesozoic Dipole Low (MDL) and the processes that govern field intensity and reversal regimes. We have conducted the first palaeosecular variation study that incorporates Triassic virtual geomagnetic pole (VGP) data, and analysed this data within the context of the average reversal frequency for the period. We observed remarkably similar VGP dispersion patterns from the late Permian, after the Permo-Carboniferous Reversed Superchron, until the onset of the Cretaceous Normal Superchron, despite fluctuating mean reversal rates. We have also completed palaeointensity experiments on samples with a range of lithologies collected from two localities in Argentina as well as pillow basalts from northern Italy. Previously published radiometric ages place our sampled lithologies across all three Triassic epochs, presenting an opportunity to populate the palaeointensity record at multiple ages across the ~50 Ma lacuna. Results were obtained utilizing a range of methods, the IZZI+ thermal Thellier, Shaw, and pseudo-Thellier. Estimates of virtual dipole moment from these experiments will be presented and discussed in the context of their reliability, and importance in better defining the MDL.</p>
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