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首页> 外文期刊>Journal of geodynamics >Controls on accommodation during the early-middle Campanian in southern Alberta, western Canada foreland system
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Controls on accommodation during the early-middle Campanian in southern Alberta, western Canada foreland system

机译：在加拿大西部南部的南部的早期坎帕尼亚南部，加拿大西部南部陆战系统

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The Western Canada Sedimentary Basin is a retroarc foreland system produced by thrust sheet loading in the Canadian Cordillera and resultant flexural displacement of the lithosphere east of the orogenic front. Theoretical models of flexural tectonism and dynamic loading have long been used to predict the effects of these controls on the creation/destruction of accommodation in retroarc foreland settings, however, few field studies have attempted to evaluate their relative contributions for a given point in geologic time. As key regional drivers of subsidence/uplift and implicitly, relative sea level rise and fall, flexural tectonism and dynamic loading impart unique signatures (subsidence geometries) which can be discerned via the spatial and temporal analysis of event significant surfaces preserved in the geologic record. We use magnetostratigraphy to constrain the timing of a major marine incursion (transgressive phase of the second-order Campanian Claggett Cycle, which spanned similar to 8 Myr in its entirety) at three locations in the southern Alberta plains where the onset of this transgression is marked by a widespread ravinement surface. A chronostratigraphic framework is presented which includes new empirical ages for stratigraphic units above and below this key surface, informally termed the Milk River 'shoulder'. The framework provides a basis for determining the earliest extents of the Claggett (Pakowki/Lea Park) sea in southern Alberta, and for characterization of its subsequent expansion during the early-middle Campanian. Although commonly depicted as a simple, westward-expanding seaway, we observe that the initial expansion of the Claggett sea in southern Alberta was more complicated and proceeded in multiple directions through time, prior to maximum transgression and the ensuing second-order regression. We interpret the Claggett sea as restricted to the Alberta foredeep at similar to 82.0 Ma, before inundating a paleotopographic high associated with a prominent basement feature in southernmost Alberta (Sweetgrass Arch) at similar to 81.0 Ma, likely establishing a connection with the Claggett sea in northern Montana. As relative sea level continued to rise, the sea reached the Rocky Mountain foothills in the west while also advancing more than 100 km eastward into the forebulge region during peak transgression (similar to 80.0 Ma). With this history established, we ascertain the overriding cause for the Claggett transgression was dynamic subsidence because (1) the magnitude, direction, and timing of relative sea level rise and the associated expansion of the Claggett sea fits published dynamic subsidence models for the Campanian of North America, and (2) several hundred metres of marine sediments are preserved on the early-middle Campanian forebulge, requiring accommodation which cannot be explained by widely accepted flexural models or eustatic estimates.
机译：加拿大西部沉积盆地是由加拿大科特里拉的推力板装载生产的retroarc原料系统，并将岩石圈的抗斜面朝向造口前部的弯曲位移。弯曲构造和动态载荷的理论模型已长期以来一直用于预测这些控制对Retroarc前陆环境中的住宿的创作/破坏的影响，然而，很少有几个现场研究试图评估他们在地质时间的给定点的相对贡献。作为沉降/隆起的关键区域驱动因素，隐含地，相对海平面上升和下降，弯曲构造和动态载荷赋予独特的签名（沉降几何），其可以通过在地质记录中保留的事件显着表面的空间和时间分析来辨别。我们使用磁体图案来限制主要海洋入侵的时间（二阶坎皮格特循环的违规阶段）在南阿尔伯塔南部平原的三个地点，跨越了与其完全同样的80R相似的地方，其中该过渡的发作标记为通过广泛的止毒表面。介绍了计时级别的框架，其中包括上方和下方的地层单位的新经验年龄，非正式称为牛奶河肩膀。该框架为确定艾伯塔省南部的Claggett（Pakowki / Lea Park）海的最早的范围提供了基础，以及在早期的坎帕尼亚时期的随后扩展的表征。虽然通常被描绘为简单，西方的膨胀海道，但我们观察到南·艾伯塔省南部的Claggett海的初始扩张更加复杂，在多个方向上通过时间进行，在最大违规和随后的二阶回归之前。我们将Claggett海域解释为仅限于82.0 mA的Alberta ForeDeep，在与81.0 mA类似的南部的艾伯塔省（Sweetgrass Arch）中的突出地下室特征淹没一个古典图高，可能与Claggett Sea建立联系蒙大拿州。随着相对海平面持续上涨，海上达到了西部的岩石山麓，同时在峰越峰（类似于80.0 MA）期间也进入前胸部地区的前沟区。凭借这个历史建立，我们确定了Claggett Trantcrous的推翻原因是动态沉降，因为（1）相对海平面上升的幅度，方向和时序和Claggett海的相关扩展为坎帕尼亚的发布动态沉降模型北美洲，（2）在早期的南美洲海洋沉积物中保留了几百米的海洋沉积物，需要住宿，这不能通过广泛接受的弯曲模型或难估计来解释。

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