Paleomagnetic directions and K/Ar dating of 0 to 1 Ma lava flows from La Guadeloupe Island (French West Indies): Implications for time‐averaged field models

摘要: Twenty-six lava flows spanning the last million years were sampled in La Guadeloupe, French West Indies. Because of lack continuous volcano-stratigraphic sections dating is necessary order to describe temporal evolution geomagnetic field this time interval. New K/Ar ages ranging from 50 ka 1 Ma have been obtained on andesites using Cassignol-Gillot technique at Universite Paris Sud-Institut de Physique du Globe Orsay laboratory. Additional (with same technique) also for paleomagnetic investigations. More than 200 samples analyzed both alternating AF and thermal stepwise demagnetization techniques. Duplicate samplings two three different sites demonstrate that within-flow dispersion negligible andesitic study. Direct comparison with an earlier study performed island indicates that, investigated flows, modern techniques yield much better defined directions. The Matuyama-Brunhes transition was recorded a three-flow section dated 781±18 ka, good agreement other recent radiometric age determinations. mean pole calculated 23 normal polarity indistinguishable geographic north, which implies no significant persistent axial quadrupole term can be identified site years. This result contradicts results has important implications models time-averaged (TAF). An Occam algorithm used construct TAF model global volcanic database 5 Ma. Substitution direction Lesser Antilles by our new value reduces more 30%. effect, produced changing data single site, demonstrates older may need reinvestigated. Furthermore, it highlights limitations inferred databases their present state.