The Chicxulub impact led to the formation of a ~ 200-km wide by ~1-km deep crater on México's Yucatán Peninsula. Over a period of hours after the impact the ocean re-entered and covered the impact basin beneath several hundred meters of water. A suite of impactites were deposited across the crater during crater formation, and by the resurge, tsunami and seiche events that followed. International Ocean Discovery Program/International Continental Scientific Drilling Program Expedition 364 drilled into the peak ring of the Chicxulub crater, and recovered ~130 m of impact deposits and a 75-cm thick, fine-grained, carbonate-rich “Transitional Unit”, above which normal marine sedimentation resumed. Here, we describe the results of analyses of the uppermost impact breccia (suevite) and the Transitional Unit, which suggests a gradual waning of energy recorded by this local K-Pg boundary sequence.

The dominant depositional motif in the upper suevite and the Transitional Unit is of rapid sedimentation characterized by graded bedding, local cross bedding, and evidence of oscillatory currents. The lower Transitional Unit records the change from deposition of dominantly sand-sized to mainly silt to clay sized material with impact debris that decreases in both grain size and abundance upward. The middle part of the Transitional Unit is interrupted by a 20 cm thick soft sediment slump overlain by graded and oscillatory current cross-laminated beds. The uppermost Transitional Unit is also soft sediment deformed, contains trace fossils, and an increasing abundance of planktic foraminifer and calcareous nannoplankton survivors. The Transitional Unit, as with similar deposits in other marine target impact craters, records the final phases of impact-related sedimentation prior to resumption of normal marine conditions. Petrographic and stable isotopic analyses of carbon from organic matter provide insight into post-impact processes. δ¹³C_org values are between terrestrial and marine end members with fluctuations of 1–3‰.

Timing of deposition of the Transitional Unit is complicated to ascertain. The repetitive normally graded laminae, both below and above the soft sediment deformed interval, record rapid deposition from currents driven by tsunami and seiches, processes that likely operated for weeks to potentially years post-impact due to subsequent continental margin collapse events. Highly siderophile element-enrichment at the top of the unit is likely from fine-grained ejecta that circulated in the atmosphere for several years prior to settling. The Transitional Unit is thus an exquisite record of the final phases of impact-related sedimentation related to one of the most consequential events in Earth history.

奇克卢布（Chicxulub）撞击导致墨西哥尤卡坦半岛（YucatánPeninsula）形成了约200公里宽，约1公里深的火山口。撞击后的几个小时内，海洋重新进入并覆盖了数百米水下的撞击盆地。在火山口形成过程中以及随后发生的海浪，海啸和塞奇事件中，一系列的撞击石沉积在整个火山口中。国际海洋发现计划/国际大陆科学钻探计划远征队364钻入了Chicxulub火山口的山顶环，回收了约130 m的冲击沉积物和上方75厘米厚，细粒，富含碳酸盐的“过渡单元”恢复了正常的海洋沉积。在这里，我们描述了最上部撞击角砾岩（苏维岩）和过渡单元的分析结果，

上苏维埃和过渡单元中主要的沉积基序是快速沉积，其特征为层理层理，局部交叉层理和振荡流的证据。较低的过渡单元记录了从主要为砂粒大小到主要为粉砂的沉积到具有撞击碎屑的黏土大小材料的变化，这些颗粒的粒径和丰度都减小了。过渡单元的中部被一个20厘米厚的软质沉积物坍落度中断，该沉积物被分级的和振荡的电流交叉层压床所覆盖。最上层的过渡单元也是软质沉积物变形，包含微量化石，并且浮游有孔虫和钙质纳米浮游生物幸存者数量增加。过渡股以及其他海洋目标撞击坑中的类似沉积物，在恢复正常海洋条件之前，记录与冲击有关的沉积的最终阶段。对有机物碳的岩石学和稳定同位素分析提供了对撞击后过程的了解。δ¹³ C _org值在地面和海洋末端成员之间，波动为1-3‰。

过渡部门的交接时间很难确定。在软沉积物变形间隔之下和之上的，重复的，通常为梯度的薄层，记录了海啸和seiches驱动的洋流的快速沉积，由于随后的大陆边缘塌陷事件，该过程可能在撞击后持续数周甚至数年。装置顶部高度嗜铁元素的富集可能来自沉淀之前在大气中循环了数年的细颗粒射流。因此，过渡部门是与地球历史上最重大的事件之一有关的与影响有关的沉积的最后阶段的精确记录。