Snapshot of the Matuyama-Brunhes reversal process recorded in ⁴⁰Ar/³⁹Ar-dated lavas from Guadeloupe, West Indies

We obtain new ⁴⁰Ar/³⁹Ar ages for three lavas that record part of the Matuyama-Brunhes geomagnetic field reversal process on Guadeloupe. These lavas record a reversed-transitional-reversed magnetostratigraphy and yield a weighted mean isochron age of 785.2 ± 5.2 ka (2σ analytical uncertainty) relative to an age for the Fish Canyon sanidine standard of 28.201 Ma. This age is of greater accuracy than ages obtained previously by K-Ar dating. These lavas may record directional fluctuations occurring between the Matuyama-Brunhes precursor and the final directional reversal. Such variations have been observed in some globally distributed coupled paleomagnetic and oxygen isotope marine sedimentary records of the Matuyama-Brunhes reversal. Previous paleointensity estimates from these lavas indicate reduced, but fluctuating field strength during this time. Key Points New Ar/Ar dates from lavas on Guadeloupe island Lavas record part of the Matuyama-Brunhes geomagnetic reversal process