Age determination of sediment core from the Gulf of Alaska

Micropaleontological data of core PAR87A-10 reveal that the last glacial interval, prior to 13 ka, was marked by low biogenic fluxes and poor CaCO3 preservation. Quantitative estimates of sea-surface conditions based on dinocyst assemblages suggest that cold temperatures and freezing winter conditions existed during this period. The glacial to interglacial transition, i.e., the 13–8 ka interval, was characterized by an increase in fluxes of microfossils indicating enhanced productivity in surface waters. A higher biogenic carbonate production probably resulted in better preservation of CaCO3. This interval was marked by relatively low salinity and by sea-surface temperatures increasing toward modern values. Relatively high pollen flux during the transition suggests nutrient inputs through atmospheric and/or fluvial transport from the adjacent North American continent. After 8 ka, diminished fluxes of plankton, concomitant with a decline in pollen input, are associated with decreasing nutrient supply as predominantly eastward winds became established over the North Pacific.

岩芯PAR87A-10的微古生物学数据显示，距今13 ka以前的末次冰期时段，生源通量偏低且碳酸钙（CaCO3）保存状况较差。基于沟鞭藻孢囊（dinocyst）组合对海面环境条件的定量估算结果表明，该时期存在低温与冬季冰封环境。冰期-间冰期过渡时段（即13~8 ka时段）以微体化石通量升高为特征，指示表层水生产力得到增强。更高的生源碳酸盐生产大概率改善了碳酸钙的保存状况，该时段盐度相对偏低，海面温度逐渐向现代值回升。过渡阶段相对较高的花粉通量表明，营养物质通过大气和/或河流搬运作用从邻近的北美大陆输入海洋。距今8 ka以后，浮游生物通量减少，伴随花粉输入量下降，这与北太平洋地区逐渐形成以东风为主的风场格局所导致的营养供给减少密切相关。