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

Abstract

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.

Keywords

• geomagnetic reversals
• paleomagnetism
• paleointensity
• Ar/Ar geochronology