Origin and emplacement of the impact formations at Chicxulub, Mexico, as revealed by the ICDP deep drilling at Yaxcopoil‐1 and by numerical modeling
Origin and emplacement of the impact formations at Chicxulub, Mexico, as revealed by the ICDP deep drilling at Yaxcopoil‐1 and by numerical modeling
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Yaxcopoil-1 的 ICDP 深钻和数值模拟揭示了墨西哥希克苏鲁伯撞击地层的起源和位置
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
A. Wittmann
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作者：
D. Stöffler;N. Artemieva;B. Ivanov;L. Hecht;T. Kenkmann;R. Schmitt;R. Tagle;A. Wittmann
我们介绍并解释了1511米深的ICDP Yaxcopoil-1（Yax-1）岩心的岩相学、矿物学和化学分析结果，特别强调了撞击岩单元。通过对希克苏鲁布撞击坑的形成、挖掘和动态修改的数值模型计算，并在实验室数据的约束下，推导出了Yax-1撞击地层的起源和就位以及整个撞击结构的模型。Yax-1的下部由移位的白垩纪目标岩（610米厚）形成，而上部由六个钙镁石型异地角砾岩单元（100米厚）组成。根据这些岩石单元的结构和组成以及数值模型计算，我们能够将Yax-1的七个不同的撞击诱发单元与陨石坑形成和修改的相应连续阶段联系起来，这些阶段如下：1）瞬态空洞形成，包括白垩纪"巨型块"的位移和沉积;"2）喷出物幕底部冲击熔体和岩屑碎屑的地面涌动和混合，以及瞬变空洞形成后下部苏埃维特的沉积;（3）在下部苏埃维特岩顶部沉积一薄层熔体，并向瞬态空洞坍塌的末端侧向输送和角砾化（角砾状撞击熔融岩）; 4）喷出物羽流的坍塌和喷出物羽流下部的回落物质沉积，在动态陨石坑改造结束时形成中间的苏埃维特; 5）喷出物羽流的继续坍塌和上部苏埃维特的沉积; 6）在与向内流动的大气相互作用之后，下部分选的苏埃维特的坍塌和沉积的后期阶段; 7）从喷出物羽流的最高部分回落并且熔体和固体颗粒通过重建的大气沉降以形成上部分选的苏埃维特的最终阶段; 8）一段时间后，海洋返回火山口，最上面的苏埃维特在水生条件下进行了轻微的改造。我们的结果是兼容的：a）180公里和100公里的直径的最终陨石坑和希克苏鲁布的瞬态腔，分别由几位作者先前提出的，和b）解释希克苏鲁布作为一个峰环的影响盆地，是在过渡到一个多环盆地。
We present and interpret results of petrographic, mineralogical, and chemical analyses of the 1511 m deep ICDP Yaxcopoil‐1 (Yax‐1) drill core, with special emphasis on the impactite units. Using numerical model calculations of the formation, excavation, and dynamic modification of the Chicxulub crater, constrained by laboratory data, a model of the origin and emplacement of the impact formations of Yax‐1 and of the impact structure as a whole is derived. The lower part of Yax‐1 is formed by displaced Cretaceous target rocks (610 m thick), while the upper part comprises six suevite‐type allochthonous breccia units (100 m thick). From the texture and composition of these lithological units and from numerical model calculations, we were able to link the seven distinct impact‐induced units of Yax‐1 to the corresponding successive phases of the crater formation and modification, which are as follows: 1) transient cavity formation including displacement and deposition of Cretaceous “megablocks;” 2) ground surging and mixing of impact melt and lithic clasts at the base of the ejecta curtain and deposition of the lower suevite right after the formation of the transient cavity; 3) deposition of a thin veneer of melt on top of the lower suevite and lateral transport and brecciation of this melt toward the end of the collapse of the transient cavity (brecciated impact melt rock); 4) collapse of the ejecta plume and deposition of fall‐back material from the lower part of the ejecta plume to form the middle suevite near the end of the dynamic crater modification; 5) continued collapse of the ejecta plume and deposition of the upper suevite; 6) late phase of the collapse and deposition of the lower sorted suevite after interaction with the inward flowing atmosphere; 7) final phase of fall‐back from the highest part of the ejecta plume and settling of melt and solid particles through the reestablished atmosphere to form the upper sorted suevite; and 8) return of the ocean into the crater after some time and minor reworking of the uppermost suevite under aquatic conditions. Our results are compatible with: a) 180 km and 100 km for the diameters of the final crater and the transient cavity of Chicxulub, respectively, as previously proposed by several authors, and b) the interpretation of Chicxulub as a peak‐ring impact basin that is at the transition to a multi‐ring basin.