Palaeomagnetism and K--Ar age of the Upper Ordovician Alcaparrosa Formation, Argentina

Abstract

Palaeomagnetic data from 71 hand samples of igneous rocks of Late Ordovician age exposed in western Argentina (31.3°S, 69.4°W, Alcaparrosa Formation) are given. Stable remanent magnetization was isolated in the majority of samples; they yield a palaeomagnetic pole at 56°S 33°E (N = 8, α95 = 16°). Whole rock K—Ar age determinations yield an age of 416 ± 10 Myr for a pillow lava of the Alcaparrosa Formation.