Transient intraplate sedimentation like the widespread Late Cretaceous Western Interior Seaway, traditionally considered a flexural foreland basin of the Sevier orogeny, is now generally accepted to be a result of dynamic topography due to the viscous force from mantle downwelling. However, the relative contributions of flexural versus dynamic subsidence are poorly understood. Furthermore, both the detailed subsidence history and the underlying physical mechanisms remain largely unconstrained. Here, we considered both Sevier orogenic loading and three different dynamic topography models that correspond to different geodynamic configurations. We used forward landscape evolution simulations to investigate the surface manifestations of these tectonic scenarios on the regional sedimentation history. We found that surface processes alone are unable to explain Western Interior Seaway sedimentation in a purely orogenic loading system, and that sedimentation increases readily inland with the additional presence of dynamic subsidence. The findings suggest that dynamic subsidence was crucial to Western Interior Seaway formation and that the dominant control on sediment distribution in the Western Interior Seaway transitioned from flexural to dynamic subsidence during 90–84 Ma, coinciding with the proposed emplacement of the conjugate Shatsky oceanic plateau. Importantly, the sedimentation records require the underlying dynamic subsidence to have been landward migratory, which implies that the underlying mechanism was the regional-scale mantle downwelling induced by the sinking Farallon flat slab underneath the westward-moving North American plate. The simulated landscape evolution also implies that prominent regional-scale Laramide uplift in the western United States should have occurred no earlier than the latest Cretaceous.

中文翻译：

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利用景观演化模拟研究白垩纪西部内陆海道的形成

板块内的短暂沉积，如晚白垩世西部内陆航道，通常被认为是塞维尔造山带的前陆弯曲盆地，由于地幔向下涌流的粘性力，现在被认为是动态地形的结果。但是，人们对挠曲沉降与动态沉降的相对贡献知之甚少。此外，详细的沉陷历史和潜在的物理机制在很大程度上不受限制。在这里，我们同时考虑了塞维尔造山作用和对应于不同地球动力学构造的三个不同的动态地形模型。我们使用前向景观演化模拟来研究这些构造情景在区域沉积历史上的表面表现。我们发现仅靠地表过程是无法解释纯造山带系统中西部内陆海道沉积的，而且随着动态沉降的增加，内陆的沉积也容易增加。研究结果表明，动态沉降对西部内陆海道的形成至关重要，西部内陆海域对沉积物分布的主要控制在90-84 Ma期间从弯曲向动态沉降过渡，这与共轭Shatsky海洋高原的拟建位置相吻合。重要的是，沉积记录要求其潜在的动态沉降是向陆上迁移，这意味着其潜在机理是由向西移动的北美板块下沉的法拉隆平板带引起的区域尺度地幔下沉。