Isotopic Ages and Andean Uplift

Abstract

AN outline of the research programme undertaken from University College, London, to elucidate the history of Andean Uplift in northern Chile has recently been presented in Nature¹. Locally, in the San Bartolo area, the post-Cretaceous geological history has been fairly clearly established from work carried out in 1961 (ref. 2). The chronology established, however, was entirely relative, in the absence of fossil evidence in this suite of continental sediments and volcanic rocks. Thus the San Bartolo ignimbrite formation, which is part of the Formation Liparitica of Bruggen³, was regarded by him as Miocene or younger. Other workers, however, have suggested chronologies which imply a late Pliocene or Pleistocene age⁴.