Paleomagnetism of Leg 115 Basement Rocks and Latitudinal Evolution of the Réunion Hotspot

Abstract

Paleomagnetic measurements were performed on basement cores from four Leg 115 sites (706, 707, 713, and 715). Although results have on average a good paleomagnetic quality, their interpretation is made difficult by the lack of declination control, and in some cases by insufficient averaging of secular variation, and by subsequent tectonic tilting, all of which cannot generally be corrected for. Sites 707 (64 Ma) and 715 (55-60 Ma) yield paleolatitudes that are consistent with those predicted by the hotspot motion models of Duncan and Morgan, and with the new synthetic apparent polar wander paths of Besse and Courtillot. The Site 707 results are also fully consistent with those of the Deccan Traps, as predicted by Courtillot et al. (1986). On the other hand, Sites 706 (48 Ma) and 713 (36 Ma) yield discrepant results that can be interpreted in terms of emplacement close to a ridge and subsequent tectonic tilting. Results from sediments of Site 706 studied by Schneider and Kent can fortunately be added to the two reliable basement sites to yield the latitude evolution of the hotspot from its inception at the Deccan to its present position at Reunion Island. This motion is consistent with the Morgan model and amounts to northward drift at a mean rate of about 8 mm/yr.