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Sedimentology of the Upper Pennsylvanian organic‐rich Cline Shale, Midland Basin: From gravity flows to pelagic suspension fallout
Sedimentology ( IF 2.6 ) Pub Date : 2020-10-18 , DOI: 10.1111/sed.12811
Junwen Peng 1
Affiliation  

Although deep‐water fine‐grained sedimentary rocks comprise approximately two‐thirds of the stratigraphic record, the transportation and depositional processes are poorly understood compared with their shelf counterparts. This study reports the range of fine‐grained sedimentary rock lithofacies, transport, and depositional processes and cyclicities recorded in deep‐water deposits on the basis of three continuous cored wells from the Upper Pennsylvanian Cline Shale, Midland Basin, USA, with the goal of elucidating general principles that can inform synthesis depositional models for deep‐water fine‐grained sedimentary systems. A combination of sedimentological, petrographic and bulk geochemical analysis has defined seven lithofacies that stack in a repeated pattern to constitute ca 8 to 20 m thick composite cycle sets. The lower unit of each composite cycle set is characterized by basal siliciclastic‐rich lithofacies interpreted to record dilute, low‐density turbidity currents, potentially derived from hyperpycnal input which grade upward into carbonate‐rich lithofacies interpreted as debris‐flow deposits or pelagic suspension deposits. The upper unit of each composite cycle set is characterized by basal carbonate‐rich lithofacies interpreted as debris‐flow deposits or pelagic suspension deposits which grades upward into siliciclastic‐rich lithofacies interpreted to record dilute, low‐density turbidity currents, potentially derived from hyperpycnal input. The cyclicities recorded in the Cline Shale are believed to be controlled by high‐amplitude glacioeustatic sea‐level fluctuation (mean: ca 100 m). The siliciclastic‐rich lithofacies, potentially derived from hyperpycnal turbidity flows, were deposited during sea‐level lowstand, when siliciclastic sediment‐transport systems extended across the wide Eastern Shelf and deltas developed at the shelf margin. Carbonate‐rich lithofacies are interpreted to be deposited from debris flows or pelagic suspension fallout during sea‐level highstand when carbonate platforms were developed on the surrounding shelves. The prevalence of sediment density flow deposits, even in distal basin floor environments, challenges the conventional model that deep‐water fine‐grained sedimentary rocks are dominantly background sedimentation.

中文翻译:

中部盆地宾夕法尼亚州上有机质丰富的克林页岩的沉积学:从重力流到中上层悬浮物沉降

尽管深水细粒沉积岩约占地层记录的三分之二,但与陆架相比,人们对其运移和沉积过程了解甚少。这项研究报告了以美国中部盆地上宾夕法尼亚州克莱恩页岩的三个连续取芯井为基础,在深水沉积物中记录的细粒沉积岩岩相,运移,沉积过程和周期性的范围,目的是:阐明了可以为深水细颗粒沉积系统的合成沉积模型提供依据的一般原理。沉积学,岩石学和整体地球化学分析的结合,定义了七个岩相,这些岩相以重复的方式叠加以构成岩心。8至20 m厚的复合循环装置。每个复合循环组的下部单元的特征是富含基底硅质碎屑岩相,被解释为记录稀薄的低密度浊流,其可能来自于高比丘岩输入,向上逐渐变为富含碳酸盐岩相,被解释为泥石流沉积物或浮游悬浮物沉积物。 。每个复合循环组的上部单元的特征是富含碳酸盐的基底岩相被解释为泥石流沉积物或浮游悬浮沉积物,这些沉积物向上逐渐演变成富含硅质碎屑岩相,被解释为记录稀薄的低密度浊流,这可能来自于高纯的输入。 。据认为,克林页岩中记录的周期性受高幅度冰川恒流海平面波动的控制(平均值:ca100 m)。富含硅碎屑岩的岩相可能来自高比浊浊流,沉积于海平面低位,当时硅碎屑沉积物-输运系统扩展到整个东部大陆架,而三角洲则在陆架边缘发育。碳酸盐岩富集岩相被解释为在海床高位期周围的架子上发育碳酸盐岩平台时,由泥石流或浮游悬浮物沉降所沉积。沉积物密度流沉积物的普遍存在,甚至在盆地的远端底板环境中,也挑战了传统模型,即深水细粒沉积岩主要是背景沉积。
更新日期:2020-10-18
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