Dating of Holocene fluvial deposits in the southern Sierras Pampeanas (Argentina) by matching paleomagnetic secular variation to a geomagnetic field model

GOGORZA, C.S.G.; IRURZUN, M.A.; HEIDER, G.; GOGUITCHAICHVILI, A.; OJEDA, G.; CHIESA, J.; GRECO, C.

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2020 vol. 106

0895-9811

A 2-m long Holocene sedimentary sequence collected from a fluvial systemlocated in the eastern piedmont of Sierra de Las Quijadas (San Luis, Argentina)was dated by comparing its paleomagnetic secular variation (PSV) record withthe SHA.DIF.14 k time-varying spherical harmonic geomagnetic field model. Rockmagnetic data suggest that the magnetic signal is mainly carried bylow-coercivity magnetic minerals like magnetite. Low field magneticsusceptibility, used as a magnetic concentration parameter, shows a variationof about a factor of two along the profile. Progressive demagnetizationexperiments of the natural remanent magnetization show the presence of a stablemagnetic component, and the Characteristic Remanent Magnetization directionsare well defined (MAD <5◦). The obtained magnetic inclination, declination,and the relative paleointensity (RPI) records were then compared withpreviously published lacustrine Holocene records from Argentina. Several commonfeatures and similar millennial-scale fluctuations are observed among therecords, supporting a common geomagnetic origin. The consistency and good matchamong natural archives on a broader scale in different Argentinian regionssuggest that the PSV records of El Chimborazo site are reliable and can thus beused to better constrain the secular variation path of the geomagnetic field inthis area.