Department of Earth Sciences, Royal Holloway University of London, Egham, UK.
Departamento de Estratigrafía y Paleontología, Universidad de Granada, Granada, Spain.
Sci Rep. 2019 Nov 27;9(1):17713. doi: 10.1038/s41598-019-54246-3.
Although bioturbation is commonly recognized in contourites, only a few studies have analyzed the ichnological content of these deposits in detail. These studies have mainly focused on meso-scale bigradational sequence (a coarsening upward followed by a fining-upward sequence resulting from variations in current velocity). Here we present data from gravitational cores collected along the NW Iberian Margin showing systematic variation in ichnological content across proximal to distal depocenters within a large-scale elongated contourite drift. Data demonstrate that tracemakers' behavior varies depending on the distance relative to the bottom current core. Trace fossils are already known to be a useful tool for studying of contouritic deposits and are even used as criterion for differentiating associated facies (e.g., turbidites, debrites), though not without controversy. We propose a mechanism by which the distance to the bottom current core exerts tangible influence on specific macro-benthic tracemaker communities in contourite deposits. This parameter itself reflects other bottom current features, such as hydrodynamic energy, grain size, nutrient transport, etc. Ichnological analysis can thus resolve cryptic features of contourite drift depositional settings.
尽管生物搅动在等深积物中很常见，但只有少数研究详细分析了这些沉积物的遗迹学内容。这些研究主要集中在中尺度双梯度层序（一种由海流速度变化引起的粗化向上 followed by 细化向上序列）上。在这里，我们展示了沿西北伊比利亚边缘采集的重力岩心的数据，这些数据显示在一个大型延伸等深积漂移的近端到远端沉积中心之间，遗迹学内容存在系统变化。数据表明，痕迹制造者的行为取决于相对于底部海流核心的距离而有所不同。遗迹化石已经被证明是研究等深积物的有用工具，甚至被用作区分相关相（例如浊积岩、碎屑流）的标准，尽管并非没有争议。我们提出了一种机制，即距离底部海流核心对特定的大型底栖痕迹制造者群落在等深积物中的影响。这个参数本身反映了其他底部海流特征，例如水动力能量、粒度、养分输送等。因此，遗迹学分析可以解决等深积漂移沉积环境的隐藏特征。
