Transitional Field Studies Using a Large Scale Database (MagIC)

Paleomagnetic studies of polarity reversals have established that they are characterized by a significant loss of field strength, and have ruled out a simple rotation of the dipole field into the opposite hemisphere. Complex directional records are often observed, but there are indications of transitional Virtual Geomagnetic Poles (VGPs) following systematic paths or tending to occupy preferred locations. However, detailed records of polarity transitions remain comparatively rare, and a comprehensive understanding of the evolving field structure requires the assembly and analysis of multiple reversal records, age information, and accompanying metadata from both lavas and sediments. Significant earlier efforts produced the IAGA TRANS database, as well as the MBD97 compilation which is restricted to the most recent Matuyama-Brunhes reversal. We are now extending this work within the Magnetics Information Consortium (MagIC), a community effort that has created an on-line database for geomagnetic, paleomagnetic and rock magnetic data. Importing of the IAGA paleomagnetic databases (TRANS, PINT, PSVRL, GPMDB, ARCHEO, MAGST and SECVR) into the MagIC database (<u>earthref.org/MAGIC</u>) continues and the completed TRANS database is being augmented by more recent papers with transitional paleomagnetic data. New data are added by either the MagIC database team or members of the community at large, and can offer the possibility of access to far more detailed information than before. The compilation of these datasets into the common framework of a searchable on-line database, along with the inclusion of metadata, will allow members of the community to more easily ask and answer their own outstanding questions about the geomagnetic reversal process. Using the advanced searches possible with the on-line MagIC database interface, we revisit the (still controversial) question of whether there are preferred VGP paths during geomagnetic polarity reversals and excursions.