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浊流沉积是陆源物质向深海搬运的主要方式,其发生对于海底扇、峡谷以及深海油气藏的形成具有重要意义。对冲绳海槽3个柱状样岩芯的研究,均发现了发生于7300~7500cal.a B.P.的浊流层。这3个浊流层S1,S2和S3的发生伴随着粒度、粘土矿物以及log(Ti/Ca)的明显变化。浊流沉积层相比正常沉积层具有粗粒组分峰值较高以及下覆的不整合构造,粒度上呈现由粗到细的正粒序构造。伴随着粒度的变化,log(Ti/Ca)也发生明显增大。A7孔位的S2浊流层的底部以及Oki01孔位的S3浊流层的上部含有火山灰层,火山玻璃含量约为80%左右。火山灰层的粒度众数约24~32μm的单峰分布。通过对比其他古气候、古环境指标,发现7300~7500 cal.a B.P.的浊流事件可能与活跃的火山地震作用以及冬季风明显增强有关。
Turbidite sedimentation is the main way for the terrestrial material to be transported to the deep sea, and its occurrence is of great significance to the formation of submarine fan, canyon and deep-sea oil and gas reservoir. In the study of three columnar cores in the Okinawa Trough, the turbidity layer occurred in 7300 ~ 7500 cal.a B.P. The occurrence of these three turbidity layers S1, S2 and S3 is accompanied by a significant change in particle size, clay minerals and log (Ti / Ca). Compared with the normal sedimentary layer, the turbidity flow sedimentary layer has a higher peak value of coarse grains and a lower unconformity structure, and the grain size presents a coarse-grained normal-grain structure. Along with the change of particle size, log (Ti / Ca) also increased obviously. At the bottom of the S2 turbid layer in the A7 hole and the volcanic ash layer in the upper part of the S3 turbid layer in the hole Oki01, volcanic glass content is about 80%. The volcanic ash layer has a monomodal distribution about 24-32 μm in size. By comparing with other paleoclimate and paleoenvironmental indicators, it is found that the turbidity events of 7300 ~ 7500 cal.a B.P. may be related to the active volcanic earthquake and the significant increase of winter monsoon.