Bulk geochemical analysis and planktonic foraminifera of sediment core GeoB7112-5

A multivariable approach utilising bulk sediment, planktonic Foraminifera and siliceous phytoplankton has been used to reconstruct rapid variations in palaeoproductivity in the Peru-Chile Current System off northern Chile for the past 19000 cal. yr. During the early deglaciation (19000-16000 cal. yr BP), our data point to strongest upwelling intensity and highest productivity of the past 19 000 cal. yr. The late deglaciation (16000-13000 cal. yr BP) is characterised by a major change in the oceanographic setting, warmer water masses and weaker upwelling at the study site. Lowest productivity and weakest upwelling intensity are observed from the early to the middle Holocene (13000-4000 cal. yr BP), and the beginning of the late Holocene (<4000 cal. yr BP) is marked by increasing productivity, mainly driven by silicate-producing organisms. Changes in the productivity and upwelling intensity in our record may have resulted from a large-scale compression and/or displacement of the South Pacific subtropical gyre during more productive periods, in line with a northward extension of the Antarctic Circumpolar Current and increased advection of Antarctic water masses with the Peru-Chile Current. The corresponding increase in hemispheric thermal gradient and wind stress induced stronger upwelling. During the periods of lower productivity, this scenario probably reversed.本研究采用基于全量沉积物（bulk sediment）、浮游有孔虫（planktonic Foraminifera）与硅质浮游植物（siliceous phytoplankton）的多变量方法，重建了智利北部海域秘鲁-智利海流系统过去19000个校准年BP（cal. yr BP）内的古生产力快速变化特征。在冰消期早期（19000~16000 cal. yr BP），本研究的数据显示该区域上升流强度与古生产力达到过去19000校准年以来的峰值水平。冰消期晚期（16000~13000 cal. yr BP）的海洋环境发生显著转变，研究区水体团（water masses）变暖，上升流强度减弱。全新世早期至中期（13000~4000 cal. yr BP），古生产力与上升流强度均处于最低水平；全新世晚期伊始（<4000 cal. yr BP），古生产力逐渐回升，这一变化主要由产硅生物活动驱动。本记录揭示的古生产力与上升流强度变化，可能源于南太平洋副热带环流（South Pacific subtropical gyre）在高生产力时期发生的大规模压缩和/或位移，这与南极绕极流（Antarctic Circumpolar Current）向北扩展、南极水体团随秘鲁-智利海流平流增强的现象一致。半球间温度梯度与风应力的相应增强进一步加剧了上升流活动；而在低生产力时期，上述海洋环境变化过程则发生逆转。