A database for the Matuyama-Brunhes magnetic reversal

Abstract

We present a paleomagnetic database, designated MBD97, comprising sedimentary and lava data for the Matuyama-Brunhes reversal transition field. Using criteria regarding suitability of the rock samples, measurement methods and temporal resolution of the data, we consider 62 different studies of the Matuyama-Brunhes reversal; of these, only 11 satisfy our selection criteria: four lava sites, one loess site, three shallow-marine sedimentary sites, and three deep-ocean sedimentary sites. We discuss our reasons for accepting or disguarding each candidate data set. We investigate the distribution of transitional virtual geomagnetic poles (VGPs); they fall along American and Asian-Australian longitudes. The spatial and temporal complexity of the data indicate that the transitional field was almost certainly nonaxisymmetric and nondipolar. The directional transition of the Matuyama-Brunhes reversal took ∼ 2300–5000 years, during which time the surface intensity fell to ∼ 10–20% of its pre- and post-transitional value. We do not find any systematic bias due to site distribution or inclination shallowing, although the errors in the data do vary over the duration of the reversal. MBD97 is a small database, but it has a fairly good geographic distribution and is suitable for studies of the Matuyama-Brunhes transition, nonetheless, it is clear that further analysis of transitions will benefit from a continued program of data collection and analysis. The data in MBD97 are listed.