HR: 17:45h
AN: T32E-08    [PDF]
TI: Did Andean Uplift Control Climate Change in the Central Andes
AU: * Hartley, A J
EM: a.hartley@abdn.ac.uk
AF: University of Aberdeen, Dept. of Geology & Petroleum Geology, King's College, Aberdeen, AB24 3UE United Kingdom
AB: Sedimentological data indicate that a semi-arid/arid climate has prevailed across the Central Andes from over 25 Ma to 4 Ma. Between 4 and 3 Ma a marked switch to hyperaridity occurred along the western margin of South America between 10 and 27 degrees South. Palaeoaltitude data, although poorly constrained, suggest that a substantial proto-Central Andean mountain range was in place between 15 and 9 Ma. Evidence for this is provided by the presence of thick successions of evaporates developed within endorheic basins in the Altiplano/Puna area. These data support the idea that the Andean rain shadow existed by 15 Ma or earlier, and that rather than changing the pre-existing climatic regime it reinforced the already arid climate. The change to hyperaridity in western South America is attributed to a combination of global climate cooling and enhanced upwelling of the Humboldt current generated by closure of the Central American Seaway between 3.5 and 3 Ma, and did not result from the rain shadow generated by Andean orogenesis. Evidence for a global causal mechanism is seen in the Namib Desert. The switch to hyperaridity in the Namib also occurred around 3 Ma but was independent of orographic effects generated by a large mountain range.
DE: 1809 Desertification
DE: 8102 Continental contractional orogenic belts
DE: 9360 South America
DE: 9604 Cenozoic
SC: Tectonophysics [T]
MN: 2003 Fall Meeting