南极半岛鲍威尔海盆南部氧同位素3期以来沉积动力环境演变

THE SEDIMENTARY HYDRODYNAMIC ENVIRONMENT OF THE SOUTH POWELL BASIN,ANTARCTIC PENINSULA SINCE MIS 3

本文基于南极半岛鲍威尔海盆南部D3-7沉积岩芯粒度分析数据,采用粒度累积概率曲线、散点图和CM图来研究古沉积环境,其中CM图效果最好。结果表明,构成D3-7岩芯的各种碎屑在搬运到研究区至沉积到海底前过程中呈静水悬浮状态;首次按照古沉积水动力环境条件,将南极半岛鲍威尔海盆南部沉积演化分成四个阶段,从单一静水沉积方式→多种沉积方式→单一静水沉积方式→多种沉积方式,并发现演化具有循环性特征。剖面中的粗组分搬运过程中需要较大的启动能量,推断物源和搬运与冰筏作用、火山活动有关。

The paleosedimentary environment of the South Powell Basin, Antarctic Peninsula since MIS 3 has been studied using systematie grain size analysis of the D3-7 sedimentary column, including grain size probability diagrams, size parameter scatter diagrams, and CM patterns （ C and M are eorresponding 1% and 50% particle sizes in Ф unit in probability cumulative grain size curve, respectively）. The results show that the sediment was mainly present in hydrostatic suspension before arriving at the sea bottom. The sedimentary column can be divided into four stages on the basis of the oecurrence of different sedimentary hydrodynamic environments, which occur cyclically. The first stage is from 35.0 ka to 33.4 ka, between the bottom of D3-7 （319 cm） and 241 cm, and belongs to single hydrostatic suspended deposition. The second stage is from 33.4 ka to 29.6 ka, between 241 cm and 143 em, and belongs to multi hydrostatic suspended deposition. The third stage is from 29.6 ka to 26.8 ka, between 143 cm and 52 era, and again belongs to single hydrostatic suspended deposition. The fourth stage is from 26.8 ka to 0 ka, between 52 cm and the top of D3-7, and belongs to multi hydrostatic suspended deposition. The transport of coarse sediments requires large starting power, and so we infer that some sediment transport was performed by ice rafting and volcanic activity.