The variation of intensity of earth’s magnetic field with time

A new and larger database is established to assess the variation of paleointensity with time. It is shown that submarine basaltic glass probably contains a grain-growth chemical remanent magnetization in magnetite. Intensity estimates from these samples are used to establish a lower bound estimate on intensities. Statistical tests on various subsets of the database are used to establish a more reliable database for finding long-term trends of the paleointensity. We can obtain a reasonable estimate for intensity versus time for the Cenozoic but not for the Mesozoic or late Paleozoic. The distributions of data as a function of time also provide valuable information. In particular, the two well-documented superchrons exhibit different intensity properties, which suggests that there is not a simple correlation between reversal rate and intensity.