Cyclic sedimentation at sites 745 and 746
Cyclic sedimentation at sites 745 and 746
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745 和 746 地点的循环沉积
DOI：
10.2973/odp.proc.sr.119.123.1991
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发表时间：
1991
期刊：
影响因子：
--
通讯作者：
H. Grobe
中科院分区：
文献类型：
--
作者：
W. Ehrmann;H. Grobe
澳大利亚-南极盆地ODP 745和746地点的上中新世至更新世沉积物具有旋回相变化特征。第四纪精细剖面沉积学研究表明，a相以硅质微化石含量高、陆源沉积物含量相对较低、浮冰组分、细沉积颗粒浓度低、蒙脱石含量相对较高为主。该相对应于间冰期沉积条件。相比之下，B相是冰川条件的特征，主要由大量的陆源物质和较小的蛋白石组成。还有一个突出的冰筏部分。微化石通常被改造和破坏。黏土矿物组合显示出较高比例的冰川衍生伊利石和绿泥石。四种不同的过程（归因于冰期-间冰期旋回）的组合导致了第四纪旋回相的变化：重力、冰和洋流的输送以及初级生产力的变化。重要的是冰架接地线的移动，它直接影响到浮冰的强度和向深海的重力沉积物输送。冰架的延伸也造成了南极底水的冷蚀作用，控制了研究区域的粒度分布，特别是细粒级的粒度分布。
The upper Miocene to Pleistocene sediments recovered at ODP Sites 745 and 746 in the Australian-Antarctic Basin are characterized by cyclic facies changes. Sedimentological investigations of a detailed Quaternary section reveal that facies A is dominated by a high content of siliceous microfossils, a relatively low terrigenous sediment content, an ice-rafted component, low concentrations of fine sediment particles, and a relatively high smectite content. This facies corresponds to interglacial sedimentary conditions. Facies B, in contrast, is characteristic of glacial conditions and is dominated by a large amount of terrigenous material and a smaller opaline component. There is also a prominent ice-rafted component. The microfossils commonly are reworked and broken. The clay mineral assemblages show higher proportions of glacially derived illite and chlorite.A combination of four different processes, attributed to glacial-interglacial cycles, was responsible for the cyclic facies changes during Quaternary time: transport by gravity, ice, and current and changes in primary productivity. Of great importance was the movement of the grounding line of the ice shelves, which directly influenced the intensity of ice rafting and of gravitational sediment transport to the deep sea. The extension of the ice shelves was also responsible for the generation of cold and erosive Antarctic Bottom Water, which controlled the grain-size distribution, particularly of the fine fraction, in the investigated area.