Facies architecture of individual basin‐plain turbidites: Comparison with existing models and implications for flow processes
Facies architecture of individual basin‐plain turbidites: Comparison with existing models and implications for flow processes
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DOI：
10.1111/j.1365-3091.2012.01329.x
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发表时间：
2012-10
期刊：
影响因子：
3.5
通讯作者：
E. Sumner;P. Talling;L. Amy;R. Wynn;C. Stevenson;M. Frenz
中科院分区：
文献类型：
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作者：
E. Sumner;P. Talling;L. Amy;R. Wynn;C. Stevenson;M. Frenz
目前对海底沉积物密度流动的了解很大程度上是基于它们的沉积物，因为这种流动是众所周知的难以直接监测的。然而，很少有可能在相当远的距离上追踪单个矿床的相结构。相反，推断“典型”矿床结构的床尺度相模型概括了目前对沉积过程和流动演化的理解。在这项研究中，在超过100公里的距离上，沿着下游的样带记录了12个单独层的相分布。这些矿床位于意大利东北部中新世Marnoso Arenacea组相对平坦的盆地-平原环境和摩洛哥近海晚第四纪Agadir盆地。统计分析表明，最常见的垂向相转换序列与已建立的相模型大致相似。然而，单个层的制图表明，它们通常在几个重要方面偏离广义模型，包括：(i)平行层状砂的丰度，表明该相的沉积来自高密度和低密度浊度流；（ii）三种截然不同的粒度破碎类型，表明粉质沉积物的蜡质流、侵蚀裂缝和旁路；（iii）富泥碎屑的存在表明混合流动沉积；（iv）中细粒砂岩的沙丘尺度交叉层理。海底沉积物密度流在盆地-平原环境中流过相对简单的地形。然而，它们的沉积记录了复杂的流动事件，涉及不同流动类型之间的转换，而不是浊积岩系统远端部分常见的简单的减弱涌流。
Current understanding of submarine sediment density flows is based heavily on their deposits, because such flows are notoriously difficult to monitor directly. However, it is rarely possible to trace the facies architecture of individual deposits over significant distances. Instead, bed‐scale facies models that infer the architecture of ‘typical’ deposits encapsulate current understanding of depositional processes and flow evolution. In this study, the distribution of facies in 12 individual beds has been documented along downstream transects over distances in excess of 100 km. These deposits were emplaced in relatively flat basin‐plain settings in the Miocene Marnoso Arenacea Formation, north‐east Italy and the late Quaternary Agadir Basin, offshore Morocco. Statistical analysis shows that the most common series of vertical facies transitions broadly resembles established facies models. However, mapping of individual beds shows that they commonly deviate from generalized models in several important ways that include: (i) the abundance of parallel laminated sand, suggesting deposition of this facies from both high‐density and low‐density turbidity current; (ii) three distinctly different types of grain‐size break, suggesting waxing flow, erosional hiatuses and bypass of silty sediment; (iii) the presence of mud‐rich debrites demonstrating hybrid flow deposition; and (iv) dune‐scale cross‐lamination in fine‐medium grained sandstones. Submarine sediment density flows in basin‐plain settings flow over relatively simple topography. Yet, their deposits record complex flow events, involving transformation between different flow types, rather than the simple waning surges often associated with the distal parts of turbidite systems.