很抱歉,出错啦!

您现在的位置: 荒漠生态综合整治技术推广系统>> 知识查询>> 文献查询>>正文内容

    Sand wave fields beneath the Loop Current, Gulf of Mexico: reworking of fan sands

    点击数: 【字体: 收藏 打印文章
     

    Abstract
    Extensive fields of large barchan-like sand waves and longitudinal sand ribbons have been mapped by deep-towed SeaMARC IA sidescan sonar on part of the middle and lower Mississippi Fan that lies in about 3200 m of water. The area is beneath the strongly flowing Loop Current. The bedforms have not been adequately sampled but probably consist of winnowed siliciclastic-foraminiferal sands. The size (about 200 m from wingtip to wingtip) and shape of the large barchans is consistent with a previously observed peak current speed of 30 cm/s, measured 25 m above the seabed. The types of small-scale bedforms and the scoured surfaces of chemical crusts, seen on nearby bottom photographs, indicate that near-bed currents in excess of 30 cm/s may sometimes occur. At the time of the survey the sand transport direction was to the northwest, in the opposite direction to the Loop Current but consistent with there being a deep boundary current along the foot of the Florida Escarpment. Some reworking of the underlying sandy turbidites and debris flow deposits is apparent on the sidescan sonar records. Reworking by deep-sea currents, resulting in erosion and in deposits characterised by coarsening upwards structures and cross-bedding, is a process that has been proposed for sand found in cores in shallower parts of the Gulf of Mexico. This process is more widespread than hitherto supposed.
    Article Outline
    1. Introduction
    2. Existing data
    3. Data acquisition
    4. New observations
    5. Discussion
    6. Summary
    Acknowledgements
    References
     

    DOWNLOAD


    作者:Kenyon, N. H., Akhmetzhanov, A. M., Twichell, D. C. 来源:Elsevier 发布时间:2011年07月12日