The Process of Reconstructing the Ancient Magnetic Field Direction: A New Approach to Paleomagnetic Data for a Better Estimate of Accuracy

Traditionally, the accuracy of paleomagnetic data obtained from samples of igneous rocks relies on the widely known method a95. We propose here a novel statistical method to estimate the ancient field direction using information from Zijderveld diagrams. We show a way to detect outliers in a sample of directions by constructing a confidence domain (convex, but complex in shape) on the direction sphere. Such a region statistically localizes the common direction of the ancient field over a given set of specimens from the lava flow. Often, even for a small sample, this confidence domain is much smaller than the confidence domain that the a95 method gives for the average direction over the sample. Improving the accuracy is obviously important for describing the evolution of the magnetic field.