摘要
氧同位素剩余值(Δδ)是指从浮游有孔虫氧同位素中扣除温度和全球冰量效应后得到的剩余值,它一般被用作海水古盐度变化的代用指标。文中给出了南海北部三个柱状样在氧同位素6期至5期(MIS6-5)和MIS2-1期间Δδ的变化曲线。末次冰期与全新世和倒数第二次冰期与末次间冰期的对比表明,Δδ在冰期比随之而来的间冰期低。冰期海平面下降和海岸线前移可能是冰期Δδ及盐度相对降低的原因。但在定量了解海平面下降、珠江口前移及现代盐度的分布情况后,笔者否定了海平面下降对Δδ变化的主要影响。因此,冰期南海地区降水相对增大和气候变湿可能是导致冰期Δδ偏低的主要原因。末次间冰期与全新世相比,Δδ明显增大,表明海水盐度增加。这可能与末次间冰期期间由于表层海水温度较高,厄尔尼诺事件频繁和海水蒸发量较大有关。
Oxygen isotope residual （△δ） is the value of planktonic foraminiferal oxygen isotope from which the effects of ambient sea surface water and of global ice-volume are deducted. △δ is usually used as a proxy for changes in sea surface paleosalinity. In this paper, △δ variations from Marine Isotope Stage 6 to 5 （MIS 6-5） and MIS 2-1 from three cores in the northern South China Sea are reconstructed. The comparisons between the glaciations and interglaciations demonstrate that △δ displays negative excursions during glaciations relative to the following interglaciations. Sea-level drop and coastal advance is the possible cause of low salinity during glaciations. However, this cause is not confirmed after we quantitatively investigate the relationships between sea-level drop, advance in Pearl River mouth, and modem salinity distributions. Consequently, higher precipitation and wetter climate during glaciations may be the main cause of the negative △δ excursions. The comparison between the last interglaciation and the Holocene shows that the last interglaciation has higher △δ values, suggesting higher salinities during this time. This is possibly related to the higher sea surface temperatures during the last interglaciation, which could cause frequent E1 Nifio events and higher sea water evaporation.
出处
《地学前缘》
EI
CAS
CSCD
北大核心
2006年第1期199-204,共6页
Earth Science Frontiers
基金
国家自然科学基金资助项目(40103006)
科学技术部"973"项目(200078500)
关键词
氧同位素剩余值
海平面变化
盐度
降水
冰期-间冰期
南海北部
oxygen isotope residual
sea-level change
salinity
precipitation
glacial-interglaeial
northern South China Sea
