Geomagnetic paleointensity dating of mid-ocean ridge basalts from the neo-volcanic zone of the Central Indian Ridge

Abstract

AbstractBy utilizing absolute paleointensity (API) measurements obtained from seafloor lava as a unique age indicator, the time interval between successive lava eruptions can be estimated. Particularly, measuring APIs from non-glass portions of seafloor basalts, which constitute the majority of basalts, is of great importance. In this study, we adopted the Tsunakawa–Shaw method to measure APIs of whole-rock seafloor basalt samples collected from the Central Indian Ridge. We conducted the experiments on a total of 18 specimens (two of three specimens from each of eight lava sites). Three specimens from each of the two lava sites, in total six specimens, passed the statistical acceptance criteria. The site-level means were 33.0 ± 1.0 µT and 35.8 ± 1.7 µT from pillow and sheet lavas, respectively. The similar API site-level means obtained from lavas with different morphologies suggest that they erupted within a short period. These site-level means are approximately 0.7 to 0.8 times the present geomagnetic intensity of 46.0 µT at the diving sites. By comparing the two site-level means with the geomagnetic intensity curves calculated from the reference geomagnetic and paleomagnetic models, we can conclude that the lavas erupted older than 1590 CE or 1530–1620 CE.