Abstract
State-of-the-art measurements of the direction and intensity of Earth’s ancient magnetic field have made important contributions to our understanding of the geology and palaeogeography of Precambrian Earth. The PALEOMAGIA and PINT(QPI) databases provide thorough public collections of important palaeomagnetic data of this kind. They comprise more than 4,100 observations in total and have been essential in supporting our international collaborative efforts to understand Earth's magnetic history on a timescale far longer than that of the present Phanerozoic Eon. Here, we provide an overview of the technical structure and applications of both databases, paying particular attention to recent improvements and discoveries.
Highlights
Background & summaryThe Precambrian, 540–4,567 million years ago (Ma), spans nearly 90% of geological history and yet far less is understood about its geological processes, shallow and deep, than about the subsequent Phanerozoic Eon
Knowledge of the Precambrian geology owes much to palaeomagnetism, the study of the direction and intensity of the Earth’s ancient magnetic field
Palaeomagnetic information is preserved in ferromagnetic minerals of rocks and sediments and it can be discovered after demagnetization, the removal of the present day field vector from samples in laboratory conditions to reveal the original thermoremanent magnetization
Summary
The Precambrian, 540–4,567 million years ago (Ma), spans nearly 90% of geological history and yet far less is understood about its geological processes, shallow and deep, than about the subsequent Phanerozoic Eon. Estimates of ancient magnetic intensities (palaeointensity) have proven invaluable for constraining the thermal evolution of the deep Earth[12,13] For these data, we have established a separate database called PINT (http://earth.liv.ac.uk/pint/). We have recently assigned a comprehensive quality metric (QPI ) to all Precambrian palaeointensity values in PINT, alongside recent additions from rocks of all ages[14] (http://qpi.wikispaces.com/) These criteria are reminiscent of the directional quality grading[15] but always applied at a site mean level. The new dataset, referred to as PINT(QPI), follows the arrangement of the original PINT database, and incorporates: age, location, and lithology of the palaeointensity measurements; site-level palaeomagnetic directional information; and measurement details such as experiment type, number of specimens and standard deviation used for the calculation of the virtual axial dipole moment. The debate, over the inner core age still continues[18]
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