Climatic control of turbidite deposition on the Madeira Abyssal Plain
Climatic control of turbidite deposition on the Madeira Abyssal Plain
复制标题
马德拉深渊平原浊积岩沉积的气候控制
作者：
P. Weaver;A. Kuijpers
对马德拉深海平原西南部沉积作用的研究表明，在数千平方公里的范围内存在一系列浊积岩。浊积岩是浊流搬运的沉积物，代表快速堆积的沉积单元1，在这种情况下，在浊流的远端部分，它们是非常细的颗粒和均匀的，偶尔有粉砂质基底。个别浊积岩由薄的远洋单位分隔，这些单位从软泥到远洋粘土交替出现。结合颗石分布和岩性变化，这些远洋单位的地层学已经产生，这使得比较的核心只包含远洋沉积物从浊积岩省以外。这些比较表明，浊流在该地区没有造成显着的侵蚀。主要的浊积岩发生在岩性变化之间，反映了与冰川作用和相关的海平面升降波动有关的全球气候变化。浊积岩以前曾与海平面上升联系在一起，但仅与海平面低有关2，3。我们的工作表明，浊积岩更有可能发生在海退和海侵，而不是在平静的时期之间。
Studies of sedimentation in the southwestern part of the Madeira Abyssal Plain have revealed sequences of turbidites correlatable over thousands of square kilometres. Turbidites are sediments transported by turbidity currents and represent rapidly accumulated sedimentary units1, in this case in the distal part of the flow they are very fine-grained and homogeneous, occasionally with silty bases. Individual turbidites are separated by thin pelagic units which alternate from oozes to pelagic clays. A stratigraphy for these pelagic units has been produced from combining coccolith distributions and lithological changes, which enables comparison to cores containing only pelagic sediments from outside the turbidite province. These comparisons show that turbidity currents cause no significant erosion in the area. The major turbidites occur between lithological alternations which reflect global climate changes associated with glaciations and related eustatic sea-level fluctuations. Turbidites have been linked with eustacy on previous occasions, but only with low stands of sea level2,3. Our work shows that turbidites are more likely to occur during regressions and transgressions rather than in the quiet periods between.