An integrated paleomagnetic and multispecimen paleointensity study from the late Jurassic Zapicán dike swarm (Uruguay)

CERVANTES-SOLANO, M.; MORALES-CONTRERAS, J.; SÁNCHEZ BETTUCCI, L.; NÚÑEZ, PABLO; GOGUITCHAICHVILI, A.; GOGORZA, CLAUDIA

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2020 vol. 104

0895-9811

A rock magnetic, paleomagnetic and absolute intensity studywas conducted on 21 basic dike swarms situated in the Zapicán area (Lavalleja,Uruguay). Paleomagnetic directions revealed mostly normal polaritymagnetizations with few intermediate and reverse polarity dikes. Combining datafrom a previous study, a mean paleodirection obtained is Dec = 3.5°, Inc = −50.6°, α95 = 6.3°, N = 19, corresponding to a paleomagnetic pole PLat = 86.4°S, PLong = 178.9° E, A95 = 7.2°. This pole position coincides, withinuncertainties, with other poles proposed for the same region and age. Thepaleomagnetic intensities obtained by the multispecimen method includingfraction and domain state corrections yielded values from 13.4 to 66.5 μT (andfrom 2.5 to 12.4 1022 Am2 in terms of virtual axial dipole moments).This indicates that the geomagnetic field probably experienced relatively high fluctuationsat the end of the Jurassic Hyperactivity Period (more than 10 reversals permillion years) questioning the relationship between the strength of thegeomagnetic field and reversal rate.