Paleomagnetism of Upper Triassic rocks in the Los Colorados hill section, Mendoza province, Argentina

Abstract

Different authors have highlighted a systematic disagreement between Late Carboniferous-Triassic paleomagnetic poles (PPs) for Gondwanaland and Laurasia when they are repositioned in a classical reconstruction prior to the breakup of Pangea A. This disagreement has been interpreted in geodynamic terms or as an evidence of non-dipole components of the geomagnetic field. Such analyses have been made using data on South American PPs published approximately 25 years ago and obtained using outdated methodologies. In this article, the authors present new Late Triassic paleomagnetic data from rocks that crop out in the Pre-Andean ranges (Precordillera) of Mendoza province (Argentina). Samples of different lithologies were taken from two limbs of a doubly plunging syncline, and several field tests of paleomagnetic stability were applied. The results indicate primary site mean directions that yield a PP with geographic coordinates and statistical parameters as follows: Lat.=76°S, Lon.=280°E, N=12, R=11.63, α95=8°, K=30.2. This PP agrees with mean PPs of Laurasia of similar ages in different models of Pangea A, indicating that the hypothesis of a dipolar paleomagnetic field could be valid for the Late Triassic.