Strong El Nino events during the early Holocene: stable isotope evidence from Peruvian sea shells

Intrashell oxygen and carbon stable isotope profiles ( delta(18)O, delta(13)C) were established for Mesodesma donacium shells from the preceramic archaeological site, Quebrada de los Burros in coastal southern Peru, to reconstruct the sea- surface temperature ( SST) variations and to estimate changes of the El Nino- Southern Oscillation ( ENSO) interannual variability from the early Holocene to the present. Very strong oxygen isotopic excursions attributed to El Nino events are evident in three shells dated between 9 and 7.9 ka. This indicates that short and strong warm events were breaking the mean cooler surface conditions ( 2 - 3degreesC cooler compared with today SSTs) in relation with an intense upwelling system. At 4.8 ka, slightly lower mean SST ( cooler than today by 0.7degreesC) and a reduced seasonality confirms the previous hypothesis of a weak ENSO variability at this period.