@article{fdi:010054381, title = {{T}he {L}aschamp geomagnetic dipole low expressed as a cosmogenic {B}e-10 atmospheric overproduction at similar to 41 ka}, author = {{M}{\'e}nabr{\'e}az, {L}. and {T}houveny, {N}icolas and {B}ourl{\`e}s, {D}.{L}. and {D}eschamps, {P}ierre and {H}amelin, {B}. and {D}emory, {F}.}, editor = {}, language = {{ENG}}, abstract = {{A}uthigenic {B}e-10/{B}e-9 ratio measurements were performed at high resolution along a {P}ortuguese {M}argin deep-sea core (37 degrees 48 {N}; 10 degrees 09 {W}) spanning the 20-50 ka time interval, in order to reconstruct variations in atmospheric cosmogenic {B}e-10 production rates and derive the related geomagnetic dipole moment modulation. {A} complementary approach consisting in {T}h-230(xs)-normalized {B}e-10 deposition rate determination on selected samples confirmed the reliability of the authigenic {B}e-10/{B}e-9 record. {T}his study constitutes the first successful comparison of the two widely-used normalization techniques of {B}e-10 concentrations. {F}or both methods, the presented results herein evidence a factor of similar to 2 cosmogenic nuclide overproduction linked to a minimum dipole moment associated with the {L}aschamp {E}xcursion. {T}he latter is stratigraphically constrained beneath {H}einrich {E}vent 4. {I}ts age is estimated at similar to 41 ka on the basis of direct correlation between the series of rapid paleoclimatic events recorded in the {P}ortuguese {M}argin sediments and in the {G}reenland ice sheet, and is confirmed by calibrated radiocarbon dating carried out on the same sediments. {T}he remarkable agreement between the authigenic {B}e-10/{B}e-9 and the {G}reenland {I}ce cores {B}e-10 deposition rate records attests to their global significance. {T}his new authigenic {B}e-10/{B}e-9 record has been combined with that previously obtained at the same site to produce a stacked record that is calibrated using absolute values of {V}irtual {D}ipole {M}oment determined on lava flows. {T}his provides a reconstruction of dipole geomagnetic moment variations over the 20-50 ka interval, independent from paleomagnetically-constrained methods, that documents the {L}aschamp dipole low but fails to express any dipole low related to the {M}ono {L}ake {E}xcursion. {T}his high resolution record responds to the necessity of supplementing the knowledge of the atmospheric {D}elta {C}-14 variations in the 30-45 ka interval during which the {C}-14 calibration curve suffers from a lack of accurate data, and during which a discrepancy of about 5500 yr between the {C}-14 and {U}-{T}h ages is due to the {L}aschamp geomagnetic dipole low. {S}uch new high resolution datasets from records obtained from different latitudes will be required to make significant advances in understanding the causes of atmospheric {D}elta {C}-14 variations.}, keywords = {cosmogenic nuclides ; atmospheric {B}e-10 production rate ; geomagnetic ; dipole moment ; {L}aschamp {E}xcursion ; marine sediments ; {FRANCE}}, booktitle = {}, journal = {{E}arth and {P}lanetary {S}cience {L}etters}, volume = {312}, numero = {3-4}, pages = {305--317}, ISSN = {0012-821{X}}, year = {2011}, DOI = {10.1016/j.epsl.2011.10.037}, URL = {https://www.documentation.ird.fr/hor/fdi:010054381}, }