The partitioning of different grain‐size classes in gravity flow deposits is one of the key characteristics used to infer depositional processes. Turbidites have relatively clean sandstones with most of their clay deposited as part of a mudstone cap or as a distal mudstone layer, whereas sand‐bearing debrites commonly comprise mixtures of sand grains and interstitial clay; hybrid event beds develop alternations of clean and dirty (clay‐rich) sandstones in varying proportions. Analysis of co‐genetic mudstone caps in terms of thickness and composition is a novel approach that can provide new insight into gravity flow depositional processes. Bed thickness data from the ponded Castagnola system show that turbidites contain more clay overall than do hybrid event beds. The Castagnola system is characterized by deposits of two very different petrographic types. Thanks to this duality, analyses of sandstone and mudstones composition allow inference of which proportion of the clay in each of the deposit types was acquired en route. In combination with standard sedimentological observations the new data allow insight into the likely characteristics of their parent flows. Clean turbidites were deposited by lower concentration, long duration, erosive, muddy turbidity currents which were more efficient at fractionating clay particles away from their basal layer. Hybrid event beds were deposited by shorter duration, higher‐concentration, less‐erosive sandier flows which were less efficient at clay fractionation. The results are consistent with data from other turbidite systems (for example, Marnoso‐arenacea). The approach represents a new method to infer the controls on the degree of clay partitioning in gravity flow deposits.

中文翻译：

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浊积岩和混合事件床中泥浆的成因：从 Castagnola 浊积岩系统（意大利西北部）的积水泥岩盖层洞察

重力流沉积物中不同粒度类别的划分是用于推断沉积过程的关键特征之一。浊积岩具有相对干净的砂岩，大部分粘土沉积为泥岩盖的一部分或作为远端泥岩层，而含砂碎屑通常由砂粒和间隙粘土的混合物组成；混合事件床形成不同比例的清洁和肮脏（富含粘土）砂岩的交替。从厚度和组成方面分析共生泥岩盖层是一种新方法，可以为重力流沉积过程提供新的见解。来自积水 Castagnola 系统的床层厚度数据表明，浊积岩总体上比混合事件床含有更多的粘土。Castagnola 系统的特点是两种非常不同的岩相类型的沉积物。由于这种二元性，对砂岩和泥岩成分的分析可以推断出每种矿床类型中粘土的比例是在途中获得的。结合标准的沉积学观察，新数据可以深入了解其母流的可能特征。干净的浊流沉积在浓度较低、持续时间长、侵蚀性、泥质浊流的作用下，这些浊流更有效地将粘土颗粒从其基底层分离开来。混合事件床是由持续时间较短、浓度较高、侵蚀性较小的砂质流沉积而成，这些流在粘土分馏时效率较低。结果与来自其他浊积岩系统（例如 Marnoso-arenacea）的数据一致。