Climate variability over the last 9900 cal yr BP from a swamp forest pollen record along the semiarid coast of Chile

Abstract

We present a fossil pollen analysis from a swamp forest in the semiarid coast of Chile (32 degrees 05'S; 71 degrees 30'W), at the northern influence zone of southern westerly wind belt. A similar to 10,000 cal yr BP (calendar years before 1950) palynological sequence indicates a humid phase characterized by dense swamp forest taxa dated between similar to 9900 and 8700 cal yr BP. The presence of pollen-starved sediments with only scant evidence for semiarid vegetation indicates that extreme aridity ensued until similar to 5700 cal yr BP. The swamp forest recovered slowly afterwards, helped by a significant increase in moisture at similar to 4200 cal yr BP. A new swamp forest contraction suggests that another slightly less intense drought occurred between similar to 3000 and 2200 cal yr BP. The swamp forest expansion begins again at similar to 2200 cal yr BP, punctuated by a highly variable climate. Comparisons between the record presented here with other records across the region imply major variations in the extent of the southern westerlies during the Holocene. This variability could have been caused either by latitudinal displacements from the present mean position of southern westerlies wind belt or by changes in the intensity of the South Pacific Subtropical Anticyclone, both of which affect winter precipitation in the region.