Comment on Major hydrological regime change along the semiarid western coast of South America during the early Holocene by Ortega et al., Quaternary Research v78. 2012 p. 513-527

MALDONADO A.; MOREIRAS S.M.

QUATERNARY RESEARCH

ACADEMIC PRESS INC ELSEVIER SCIENCE

Año: 2013 vol. 80 p. 138 - 139

0033-5894

Ortega et al. recently published a study presenting the hydrological regime changes along the semiarid coast of Chile (30-32°S) during the early Holocene. They suggest (1) a major hydrologic change from arid conditions without heavy rainfall events and local moisture associated to coastal fog to wetter conditions around 8600 cal yr BP and (2) the onset of modern ENSO influence since 5700 cal yr BP. Conversely, pollen records from the semiarid coast of Chile suggest humid conditions associated to regional rainfall at 13,000 and between 10,500- 8600 cal yr BP followed by the driest period of the Holocene until 6200 cal yr BP when a progressive increase of humidity started. Besides, the development of swamp forests just supported by coastal fog moisture seems improbable because (1) modern forests dependent on fog moisture in the semiarid coast of Chile develop on particular topographic positions and (2) modern swamp forest water isotopic signal is similar to rainfall from inland continent areas about 200masl. Finally, Ortega et al. suggest changes in the alluvial event regime since 5700 cal yr BP related to an increase in El Niño event frequency but the number of alluvial events before/after 5700 cal yr BP remains almost steady.