Hybrid event beds are the deposits from sediment gravity flows that change their rheological behavior through their passage, entraining muddy sediments and damping turbulence. Muddy facies of hybrid event beds are often associated with abundant mud clasts which show a wide variety of size and shape. The variation of clast occurrence in hybrid event beds is expected to preserve the information of entrainment and transport processes of muddy sediments in submarine density currents. However, previous analyses of hybrid event beds have focused on describing the overall clast occurrence rather than the statistical size and shape analyses because traditional shape parameters are incapable of characterizing the complex shape of mud clasts. Here, a new quantitative grain-shape analysis of mud clasts is conducted and allows visualization of the spatial variation of clast size and shape, which suggests the wide variety of origin and transport systems of entrained mud clasts. This new method revises the traditional elliptic Fourier analysis, substituting Fourier power spectra (FPS) for traditional elliptic Fourier descriptors to overcome the mirror-wise shape problem. Further, principal-component analysis is shown to capture significant shape attributes more effectively than traditional shape parameters. The proposed method is applied to mud clasts in sediment-gravity-flow deposits in the lower Pleistocene Otadai Formation, central Japan. Results imply that there are distinctive shape and size differences of mud clasts that are strongly associated with depositional facies rather than the distance from the source. The clasts have a higher angularity than other facies in the debrite intervals in hybrid event beds. It is also shown that clasts in sandy, structureless facies have different characteristics in shapes based on elongation and convexity compared to laminated facies. Comparison between different shape-analysis methods demonstrates that none of the traditional methods are able to visualize these trends as effectively as the method presented herein. These results highlight the importance of the quantitative shape analysis of sediment grains and the effectiveness of FPS-based elliptic Fourier analysis.

中文翻译：

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泥屑的形状差异取决于沉积相：新改良的椭圆傅里叶分析在混合事件床中的应用

混合事件床是来自沉积物重力流的沉积物，它们通过流路改变了其流变性，夹带了泥泞的沉积物并抑制了湍流。混合活动床的泥质相通常与丰富的泥屑相关，这些泥屑显示出各种尺寸和形状。混合事件床中碎屑发生的变化有望保留海底密度流中泥质沉积物的夹带和输送过程信息。但是，由于传统的形状参数无法表征泥屑的复杂形状，因此以前混合动力床的分析重点是描述整体碎屑的发生，而不是统计大小和形状分析。这里，进行了一种新的定量定量泥浆颗粒形状分析，可以可视化显示泥浆的大小和形状的空间变化，这表明夹带泥浆的来源和运输系统种类繁多。这种新方法修改了传统的椭圆傅里叶分析，用傅里叶功率谱（FPS）代替了传统的椭圆傅里叶描述子，从而克服了镜向形状问题。此外，与传统的形状参数相比，主成分分析显示可以更有效地捕获重要的形状属性。该方法适用于日本中部下更新世Otadai组沉积物重力流沉积物中的泥屑。结果表明，泥屑具有明显的形状和大小差异，这与沉积相密切相关，而不是与烃源的距离密切相关。在混合事件床中，碎屑岩的碎屑比其他相的棱角更高。还表明，与层压相相比，含沙无结构相的碎屑具有基于伸长率和凸度的形状特征。不同形状分析方法之间的比较表明，没有一种传统方法能够像在此介绍的方法一样有效地可视化这些趋势。这些结果突出了沉积物颗粒形状定量分析的重要性以及基于FPS的椭圆傅里叶分析的有效性。在混合事件床中，碎屑岩的碎屑比其他相的棱角更高。还表明，与层压相相比，含沙无结构相的碎屑具有基于伸长率和凸度的形状特征。不同形状分析方法之间的比较表明，没有一种传统方法能够像在此介绍的方法一样有效地可视化这些趋势。这些结果凸显了沉积物颗粒形状定量分析的重要性以及基于FPS的椭圆傅里叶分析的有效性。在混合事件床中，碎屑岩的碎屑比其他相的棱角更高。还表明，与层压相相比，含沙无结构相的碎屑具有基于伸长率和凸度的形状特征。不同形状分析方法之间的比较表明，没有一种传统方法能够像在此介绍的方法一样有效地可视化这些趋势。这些结果凸显了沉积物颗粒形状定量分析的重要性以及基于FPS的椭圆傅里叶分析的有效性。不同形状分析方法之间的比较表明，没有一种传统方法能够像在此介绍的方法一样有效地可视化这些趋势。这些结果凸显了沉积物颗粒形状定量分析的重要性以及基于FPS的椭圆傅里叶分析的有效性。不同形状分析方法之间的比较表明，没有一种传统方法能够像在此介绍的方法一样有效地可视化这些趋势。这些结果凸显了沉积物颗粒形状定量分析的重要性以及基于FPS的椭圆傅里叶分析的有效性。