These rocks represent the main stage of the rift-related magmatism. McElhinny, Michael W. This means that the pattern of normal and reverse polarity in an assemblage of rocks can be distinctive in the same way though for a completely different reason that growth rings in a tree can be distinctive. Irving  constructed apparent polar wander paths for Europe and North America. The other study by Kern et al, on rocks of the alkaline Coldwell Complex Ontario, Canada also suggests no asymmetry in geomagnetic reversal during Keweenawan time. Geological Survey. Essentials of Paleomagnetism.
Into this space is inserted another pipe with compass and inclinometer attached.
In order to collect paleomagnetic data dating beyond mya, scientists turn to magnetite-bearing samples on land to reconstruct the Earth's ancient field orientation. Fundamentals and Frontiers. So, when rocks form, the minerals align with the magnetic field preserving its position. Because complex oxidation reactions may occur as igneous rocks cool after crystallization, the orientations of the Earth's magnetic field are not always accurately recorded, nor is the record necessarily maintained. Full browser?