@article{PAR00011897,
  title = {{G}eomagnetic, cosmogenic and climatic changes across the last geomagnetic reversal from {E}quatorial {I}ndian {O}cean sediments},
  author = {{V}alet, {J}. {P}. and {B}assinot, {F}. and {B}ouilloux, {A}. and {B}ourles, {D}. and {N}omade, {S}. and {G}uillou, {V}. and {L}opes, {F}. and {T}houveny, {N}icolas and {D}ewilde, {F}.},
  editor = {},
  language = {{ENG}},
  abstract = {{H}igh-resolution records of beryllium ({B}e-10) production and relative paleointensity have been obtained across the {M}atuyama-{B}runhes ({M}-{B}) reversal from the equatorial {I}ndian {O}cean ({M}aldives area). {B}oth magnetic and geochemical analyses were performed from the same discrete samples to avoid any artificial depth offset. {T}he authigenic {B}e-10 concentrations were normalized with respect to {B}e-9 in order to correct for potential environmental effects, while the relative paleointensity was derived from the remanent magnetization intensity after accounting for changes in magnetic concentration within the sediment. {T}he relative paleointensity and the {B}e-10/{B}e-9 records are both characterized by large deviations, which culminate in the middle of the reversal. {I}n contrast to most previous studies, and despite relative high deposition rate (4.7 cm/ka), we observed a perfect synchronism between the {B}e-10/{B}e-9 peak, the lowest value of relative paleointensity and the switch in direction, which indicates that bioturbation and post-depositional processes did not affect the magnetic record. {T}his leaves no ambiguity for the stratigraphic position of the reversal located within {M}arine {I}sotopic {S}tage 19 as revealed by the planktonic delta {O}-18 record from the same core. {T}he magnetic data depict a two-phase process with a precursory event preceding the rapid polarity switch, while only the second phase is present in the {B}e-10 record, similarly to other low latitude records from the {I}ndonesian area. {U}sing an orbitally-tuned age model, we obtain an age of 772 ka +/- 5 ka for the middle of the transition, while the precursory event occurred almost 20 ka before. {W}e believe that the bimodal distribution emerging from the compilations of the ages of the {M}-{B} reversal results from the succession of these two events. {M}icrotektites from the {A}ustralasian impact were found at 0.6 m below the transition (790 ka +/- 5 ka {B}.{P}.) and confirm that this large event occurred 12 ka prior to the polarity transition. {T}he distribution of tektite abundance was used to deconvolve the {B}e-10/{B}e-9 signal. {T}he results confirm that the beryllium changes are concentrated during the transitional period, thus likely in presence of a multipolar geomagnetic field (or in the vicinity of a geomagnetic pole) that favored the penetration of cosmic rays and consequently increased the {B}e-10 production. {T}he absence of {B}e-10 during the precursor indicates that the present site and the {I}ndonesian ones were far away from a geomagnetic pole and that interlatitudinal atmospheric mixing was limited. {T}he geomagnetic pole positions above the {I}ndonesian sites during the precursor would thus be incompatible with the corresponding inclined dipolar field during this period, and suggest the dominance of low-degree harmonics.},
  keywords = {reversals ; geomagnetic field ; beryllium ; astrochronology ; magnetization ; {OCEAN} {INDIEN}},
  booktitle = {},
  journal = {{E}arth and {P}lanetary {S}cience {L}etters},
  volume = {397},
  numero = {},
  pages = {67--79},
  ISSN = {0012-821{X}},
  year = {2014},
  DOI = {10.1016/j.epsl.2014.03.053},
  URL = {https://www.documentation.ird.fr/hor/{PAR}00011897},
}