Preliminary paleomagnetic data from the Santo Domingo Formation (La Rioja, NW Argentina): chronologic and tectonic implications.

VIZÁN H., S. GEUNA, R. MELCHOR, E. BELLOSI & J. GENISE

La Plata

Congreso; XV Congreso Geológico Argentino; 2005

Asociación Geológica Argentina

ABSTRACT Paleomagnetic studies in the Santo Domingo Formation (Precordillera, NW La Rioja province) coupled with detailed structural mapping and sedimentologic logging were aimed to refine the age of the formation. The relatively large analytical error of the available radiometric age for basalt flows (212 Ma) precludes the application of the magnetostratigraphic technique at this stage of the study. However, the position of the paleomagnetic pole (PP) of the formation in a properly dated apparent polar wander (APW) path may help to constrain the age of the unit.  The preliminary PP, when compared with a recently obtained APW path after being transferred to Africa coordinates using different reconstruction parameters overlaps with the section of the path dated between 190 and 185 Ma. This correspondence would indicate that the record of the CRM took place circa 190 Ma (Early Jurassic). This date is considered slightly younger than the age of the basalts of the Santo Domingo Formation. The discrepancy between this age estimated by paleomagnetic data and the radiometric date from the basalt flows could be partially explained by the time involved in more than 150 m of stacked calcrete paleosols located above the basalt flows.