A WARM INTERGLACIAL EPISODE DURING OXYGEN-ISOTOPE STAGE-11 IN NORTHERN CHILE

Combined palaeontological, morphostratigraphic and geochronologic data from emerged Middle Pleistocene coastal deposits in Mejillones Penins ula (23 degrees S), northern Chile, strongly suggest that climatic con ditions were particularly warm during the Oxygen Isotope Stage 11 high seastand episode. An anomalous warm-water molluscan assemblage from l ocalities assigned to that interglaciation included several extralimit al species, presently living only north of 6 degrees S (or 14 degrees S), that were not present in the area during subsequent Middle and Lat e Pleistocene, or Holocene, interglacial episodes. Only two of these e xtralimital species may be found nowadays at the 23 degrees S latitude , in a protected locality, immediately after the occurrence of strong El Nino events. Many of the species of the thermally anomalous mollusc an assemblage (TAMA) are the same as those which lived in a closed sha llow lagoon near Santa, north-central Peru (9 degrees S) during a brie f mid-Holocene episode. The new findings thus indicate that lagoonal a nd protected embayments were significantly warmer than the open marine environment ca. 400 ka. Actually, the co-occurrence of cool water fau na in exposed sectors of the coastline at that time suggests that the coastal upwelling activity and the Humboldt Current effects were not s trongly reduced. The warm-water conditions prevailing in lagoons and p rotected bays during the Mid-Brunhes episode may reflect particularly warm air temperatures and distinct ocean-atmosphere: relationships tha n those prevalent nowadays. These data support the hypothesis that the Oxygen Isotope Stage 11 was the warmest interglaciation, at least in the southern hemisphere. Copyright (C) 1996 Elsevier Science Ltd