Abstract Hyperpycnal flows have been widely described in different lacustrine and marine environments but sedimentary structures and fossil content in hyperpycnites often offer limited information about the palaeoenvironmental conditions. This limitation can be improved by ichnological analysis, which has been recently used as a tool to differentiate between different type of subaqueous deposits, even though still only a few detailed ichnological studies on hyperpycnites exist. In order to bridge this gap in knowledge, a 50 m-thick package of terrestrial organic debris-rich, dominantly structureless and well-sorted sandstone bodies alternating with burrowed siltstones (Upper Miocene, Betic Cordillera, Spain) is here analyzed. This study is based on observations of a well-exposed outcrop and cores from a well drilled just behind the outcrop to bridge field-scale observational gaps. Two type of sandbodies were typified on the basis of their stratigraphic architecture, physical sedimentary structures, and ichnofacies in the fine-grained deposits embedding them: (1) Lobate to channelized-top sandstones embebbed into silty sands with dominant highly variable degree of bioturbation by Taenidium and Schaubcylindrichnus (depauperate Cruziana ichnofacies) and interpreted as proximal marine sustained hyperpycnites in prodelta settings; and (2) channelized-lobate (cut-and-fill sequence) sandstones embebbed into siltstones with dominant Nereites and Phycosiphon (Nereites ichnofacies) interpreted as distal hyperpycnites developed in offshore settings. The studied succession is interpreted to represent the progradation of a sandy hyperpycnal system along a prodelta to starved offshore setting with high variability in grain-size, benthic food and oxygen content. Results of this study suggest that a multi-scale analysis focused on trace fossils and physical sedimentary signatures is needed to get a better understanding of these river-derived sustained-flow turbidites (hyperpycnites) that are less well known than their conventional surge-type turbidite counterparts.

中文翻译：

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近海过渡超重系统的沉积学和地质学特征（上中新世，Betic Cordillera，西班牙南部）

摘要 高密度流已在不同的湖泊和海洋环境中得到广泛描述，但高密度岩中的沉积结构和化石含量往往提供有关古环境条件的有限信息。这种限制可以通过地层学分析得到改善，它最近已被用作区分不同类型水下沉积物的工具，尽管仍然只有少数关于高密度岩的详细的地层学研究。为了弥补这一知识差距，这里分析了一个 50 m 厚的富含陆地有机碎片、主要是无结构且分选良好的砂岩体，与挖掘的粉砂岩交替出现（上中新世，Betic Cordillera，西班牙）。这项研究是基于对暴露良好的露头和在露头后面钻的井中的岩心的观察，以弥补现场规模的观察差距。根据其地层构造、物理沉积构造和嵌入其中的细粒沉积物的地层相，可划分出两种类型的砂体：(1) 叶状至沟状砂岩嵌入粉砂质砂岩中，生物扰动程度差异显着。 Taenidium 和 Schaubcylindrichnus (depauperate Cruziana ichnfacies) 并解释为前三角洲环境中近端海洋持续高密度岩；(2) 沟状叶状（切填层序）砂岩嵌入粉砂岩，主要为近海环境中发育的远侧高重岩岩层，其中主要为 Nereites 和 Phycosiphon（Nereites ichnfacies）。研究的演替被解释为代表沙质超重系统沿前三角洲向饥饿的近海环境进积，其粒度、底栖食物和氧含量具有高度可变性。这项研究的结果表明，需要对痕量化石和物理沉积特征进行多尺度分析，以更好地了解这些河流衍生的持续流浊积岩（超重浊岩），这些浊积岩的知名度不如传统的浪涌型浊积岩同行。