At Tanis, a unique bi-directional sediment package occurs precisely at the Cretaceous-Paleogene (K-Pg) boundary, recording the first hours of the Paleogene in uncommonly fine temporal detail. The impact ejecta-bearing sediment package was rapidly emplaced by two massive, ∼10-m-high, potentially impact-triggered surges, that inundated a steep, deeply incised paleo river valley from the direction of the contemporaneous Western Interior Seaway (WIS). Intermingling of fresh- and salt-water fossils at Tanis, coeval brackish water indicators in the nearby region, and historical tsunami observations, suggest that the WIS paleoshoreline was nearby Tanis at K-Pg time. The interpreted timing for deposition (including ejecta infall) of ∼1–2-hr immediately post-impact precludes a direct tsunami from the Chicxulub impact site, which would have required much more than 10 hr to reach Tanis. Seismic waves from the M_w ∼ 11 Chicxulub earthquake, arriving just minutes post-impact, might have triggered the surge, for example, via seismic excitation of large water waves in the WIS, as proposed by DePalma et al. (2019, https://doi.org/10.1073/pnas.1817407116). Here, we explore this mechanism via a simple mathematical model of seismic excitation and propagation of a water wave into a shallow river and upstream. Matching the observations implies a relatively long source process time of many minutes, such as generated by Chicxulub crater rebound processes, in order to explain sufficient upriver amplitudes and advective transport. Atmospheric waves due to the expanding Chicxulub ejecta curtain might have provided a smaller, secondary contribution during triggering. Thus, the mechanism(s) for the surges at Tanis are now better-constrained, yet remain incompletely resolved.

中文翻译：

---

北达科他州塔尼斯遗址 K-Pg 边界希克苏鲁伯撞击导致海啸式涌浪沉积的可能机制

在塔尼斯，独特的双向沉积物包恰好发生在白垩纪-古近纪（K-Pg）边界处，以异常精细的时间细节记录了古近纪的最初几个小时。含有撞击喷射物的沉积物包被两个巨大的、约10米高、可能由撞击引发的海浪迅速占据，这些海浪从同时期的西部内陆航道（WIS）的方向淹没了陡峭、深切的古河谷。塔尼斯的淡水和咸水化石的混合、附近地区同期的咸水指标以及历史海啸观测表明，WIS 古海岸线在 K-Pg 时间位于塔尼斯附近。解释的沉积时间（包括喷射物流入）为撞击后约 1-2 小时，排除了从希克苏鲁伯撞击地点发生直接海啸的可能性，而海啸需要 10 个小时以上才能到达塔尼斯。来自M _w ∼ 11 Chicxulub 地震的地震波 在撞击后几分钟到达，可能触发了海浪，例如，通过 WIS 中大水波的地震激发，如 DePalma 等人提出的。 （2019，https://doi.org/10.1073/pnas.1817407116）。在这里，我们通过地震激发和水波传播到浅河和上游的简单数学模型来探索这种机制。与观测结果相匹配意味着相对较长的源过程时间（例如由希克苏鲁伯陨石坑回弹过程产生的许多分钟），以解释足够的上游振幅和平流输送。由于希克苏鲁伯喷出物幕扩张而产生的大气波可能在触发过程中提供了较小的次要贡献。因此，塔尼斯激增的机制现在得到了更好的约束，但仍未完全解决。