Absolute geomagnetic paleointensity in the Precambrian: Where do we stand?

Abstract:

Data on the long-term behavior of absolute geomagnetic intensity are crucial for understanding the origin and nature of geodynamo. The data may also provide the insight necessary for constraining the timing of important transitions within the Earth’s interior, and for investigating potential causative links between the long-term behavior of the geomagnetic field and the evolution of atmosphere and biosphere. In the absence of strict theoretical constraints, paleomagnetic data represent a principal source of information about the Precambrian field. However, paleointensity determination represents one of the most challenging aspects of paleomagnetic research so that the paleointensity database remains rather limited especially for older epochs. Detailed analysis of the Precambrian paleointensity database indicates that some accepted paleointensity values might be biased by a variety of factors including the presence of non-ideal magnetic carriers, geological and laboratory alteration, and others. In addition, the abundance of low field values in the database may reflect the effect of thermochemical remanent magnetization (TCRM). We will discuss non-conventional experimental approaches that may circumvent or mitigate some of these problems and hence result in a significant increase in the number of reliable paleointensity determinations for the Precambrian. We also will discuss the Precambrian paleointensity database in the context of current models of the long-term geomagnetic and thermal evolution of our planet.