Geography - About Atacama Desert

Geomorphology 73 (2006) 101 – 114

Antiquity of aridity in the Chilean Atacama Desert
Jonathan D.A. Clarke *
CRC LEME, Department of Geology, Australian National University, ACT 0200, Australia Received 16 December 2004; received in revised form 17 June 2005; accepted 20 June 2005 Available online 1 September 2005

Abstract The Atacama Desert of northern Chile and southern Peru has one of the longest histories of arid conditions known. Although most studies have focused on the hyper-aridity prevalent since the Miocene, all terrestrial sediments in the region from the late Triassic onwards also record evaporitic and thus arid climates. Supergene mineralization in the region did not develop under a more humid climate conducive to deep weathering, but under arid conditions. These processes may have been facilitated by hydrological changes during Miocene uplift and drainage incision, but were operational prior to the uplift. Similarly, global cooling and changes to oceanic circulation in the post Miocene period only accentuated existing conditions. A whole regolith perspective is vital to understanding the history of aridity in the Atacama Desert and its relevance to arid zone morphogenesis, regolith formation, and supergene mineralization. In particular, the long history of aridity raises the possibility that supergene mineralisation, under the appropriate conditions, form in arid environments, instead of requiring humid conditions. D 2005 Elsevier B.V. All rights reserved.
Keywords: Regolith; Palaeoclimatology; Aridity; Evaporites; Landscape evolution; Atacama Desert

1. Introduction The Atacama Desert is the driest desert in the world. Arica and Iquique (see Fig. 1 for locations of local place names in the text) have annual rainfalls of only 0.5 and 0.6 mm, respectively, while Antofagasta, Calama, and Copiapo receive 1.7, 5.7, and 12 mm each (Direccion Meteorologica De Chile, 2000). The ´ ´ Atacama Desert is the result of...