The Lower Cretaceous McMurray Formation in Alberta and Saskatchewan, Canada, comprises a series of depositional units (DUs) consisting of stacked parasequences bounded by flooding surfaces and incised by fluvio-estuarine channel belts. The fluvio-estuarine channel belts of the McMurray Fm have been the focus of numerous studies whereas the regional DUs have received substantially less attention. Of the regional DUs, Regional C (equivalent to the middle McMurray) is the most understudied, yet this interval records the history of the McMurray Formation between deposition of fluvial strata in the lower McMurray and marine facies in the upper McMurray and overlying Clearwater Formation. Determining the history of the Regional C DU is fundamental for accurately reconstructing the stratigraphic evolution of the McMurray Fm and, by extension, the early evolution of the Alberta Foreland Basin.The Regional C is divided into two DUs separated by a regionally mappable flooding surface. This surface occurs 11 to 15 m below the top of the Regional C and is traceable over a 2,550 km2 area. This flooding surface divides the thick interval of undifferentiated Regional C into a lower C2 DU and an upper C1 DU, each with a maximum thickness of < 15 m. The thickness of the C2 and C1 DUs indicates that deposition at this time also occurred in a setting of low to moderate accommodation creation, which is consistent with the rest of the McMurray Formation. The limited available accommodation space was easily surpassed by sediment supplied by the paleo-distributive channel system, leading to a basinward progradation of the shoreline.The C2 and C1 DUs are retrogradationally stacked, with the maximum regressive paleo-shoreline of C1 lying landward of that of C2. This stacking arrangement indicates that the shoreline backstepped during the early stages of transgression of the Boreal Sea. The backstepping of the paleo-shoreline from C2 to C1 time is consistent with previous studies that show continued and stepwise retrogradation and/or transgression of the paleo-shoreline from the onset of deposition in the lower McMurray Formation through to maximum transgression in the Clearwater Formation. Together, these studies demonstrate that the early drowning of the Alberta Foreland Basin was persistent and slow.

中文翻译：

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完善麦克默里组区域C沉积单元的地层格架及其对加拿大艾伯塔前陆盆地早期侵入的意义

加拿大艾伯塔省和萨斯喀彻温省的下白垩统麦克默里组包括一系列沉积单元（DUs），这些沉积单元由堆积的顺层序组成，这些层序以洪水泛滥为界，并由河口河道带切割。McMurray Fm的河口河道带一直是众多研究的重点，而区域DU则受到的关注大大减少。在区域DU中，对C区域（相当于麦克默里中部）的研究最多，但是该间隔记录了麦克默里下部河床层沉积与麦克默里上部海相到上覆的Clearwater组之间麦克默里组的历史。确定区域C DU的历史是准确重建McMurray Fm地层演化的基础，并且据此，区域C分为两个DU，每个DU由区域可绘制的洪水表面隔开。该表面出现在区域C顶部以下11至15 m，可在2,550 km2的面积上追踪。该洪泛面将未分化区域C的较厚间隔分为较低的C2 DU和较高的C1 DU，每个厚度最大为<15 m。C2和C1 DU的厚度表明，此时的沉积也发生在低到中等的适应性形成环境中，这与McMurray组的其余部分一致。古分布河道系统提供的沉积物轻易地超过了有限的可用居住空间，从而导致海岸线向盆地性扩展.C2和C1 DU倒退堆叠，C1的最大回归古海岸线位于C2的陆地向内。这种堆放方式表明，海岸线在北海海侵早期阶段后退。古海岸线从C2到C1时间的后退与先前的研究一致，该研究表明古海岸线从下麦克默里组的沉积开始到克利尔沃特组的最大海侵持续不断地逐步退缩和/或海侵。 。这些研究共同表明，艾伯塔省前陆盆地的早期溺水持续且缓慢。古海岸线从C2到C1时间的后退与先前的研究一致，该研究表明古海岸线从下麦克默里组的沉积开始到克利尔沃特组的最大海侵持续不断地逐步退缩和/或海侵。 。这些研究共同表明，艾伯塔省前陆盆地的早期溺水持续且缓慢。古海岸线从C2到C1时间的后退与先前的研究一致，该研究表明古海岸线从下麦克默里组的沉积开始到克利尔沃特组的最大海侵持续不断地逐步退缩和/或海侵。 。这些研究共同表明，艾伯塔省前陆盆地的早期溺水持续且缓慢。