Dune stratification types, which include grainfall, grainflow and ripple lamination, provide a record of the fine‐scale processes that deposited sediment on palaeo‐dune foresets. While these facies are relatively easy to distinguish in some cross‐bedded sandstones, for others – like the Permian Coconino Sandstone of northern and central Arizona – discrete stratification styles are hard to recognize at the bedding scale. Furthermore, few attempts have been made to classify fine‐scale processes in this sandstone, despite its renown as a classic aeolian dune deposit and Grand Canyon formation. To interpret depositional processes in the Coconino Sandstone, cross‐bed facies were characterized using a suite of sedimentary textures and structures. Bedding parameters were described at multiple scales via a combination of field and laboratory methods, including annotated outcrop photomosaics, strike and dip measurements, sandstone disaggregation and laser‐diffraction particle analysis, high‐resolution scans of thin sections, and scanning electron microscopy. Cross‐beds were observed to be laterally extensive along‐strike, with most dip angles ranging from the mid‐teens to mid‐twenties. While some cross‐bed sets are statistically coarser near their bases, others exhibit no significant vertical sorting trends. Both massive and laminated textures are visible in high‐resolution scans of thin sections, but laminae contacts are commonly indistinct, making normal and reverse grading difficult to define. Diagenetic features, such as stylolite seams and large pores, are also present in some samples and might indicate alteration of original textures like detrital clay laminae and carbonate minerals. Observed textures and sedimentary structures suggest that the cross‐beds may consist of grainflow and grainfall deposits, but these remain difficult to differentiate at outcrop and thin‐section scales. This characterization of fine‐scale processes will play a critical part in the development of depositional models for the Coconino Sandstone and elucidate interpretations for similar cross‐bedded formations.

中文翻译：

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二叠纪可可诺砂岩中难区分的沙丘分层类型的特征（美国亚利桑那州）

沙丘分层类型，包括颗粒下降，颗粒流和波纹叠片，提供了将沉积物沉积在古沙丘前额上的精细过程的记录。尽管在某些交叉层状砂岩中这些相相对容易区分，但对于其他岩石层（如亚利桑那州北部和中部的二叠纪可可诺砂岩），离散的层状样式在层理规模上很难识别。此外，尽管该砂岩被称为经典的风沙丘沉积物和大峡谷地层，但仍未进行任何分类精细过程的尝试。为了解释可可诺砂岩中的沉积过程，利用一套沉积质地和结构来表征跨床相。通过实地和实验室方法的结合，在多个尺度上描述了床品参数，包括带注释的露头光马赛克，走向和倾角测量，砂岩分解和激光衍射颗粒分析，薄层的高分辨率扫描以及扫描电子显微镜。观察到跨床走时横向扩展，大多数倾角范围从十几岁到二十多岁。虽然一些跨床集在统计上接近其基数，但其他集并没有明显的垂直排序趋势。在薄切片的高分辨率扫描中，可以看到块状和层状纹理，但是层状接触通常不明显，因此很难定义正向和反向渐变。一些样品中也存在成岩特征，例如：针孔石接缝和大孔隙，这可能表明原始质地发生了变化，例如碎屑粘土层和碳酸盐矿物。观察到的质地和沉积结构表明，跨床可能由颗粒流和颗粒沉积物组成，但这些仍难以在露头和薄层尺度上区分。精细过程的表征将在可可诺砂岩沉积模型的开发中发挥关键作用，并阐明对类似跨层构造的解释。