Proximal Carbonate Ejecta From the Cretaceous-Tertiary Chicxulub Impact Crater: 87Sr/86Sr Chronology, Ballistic Sedimentation, and Diagenetic Alteration

9909560FUKE在白垩纪-第三纪(KT)边界的大型撞击以尤卡坦半岛覆盖结晶基底的3公里碳酸盐台地为目标。这项研究试图通过分析希克苏鲁布陨石坑附近弹道喷发的碳酸盐沉积物来重建KT撞击的沉积物搬运动力学和地球化学。这些矿床的年龄、来源、运移机制和沉积后的蚀变将在伯利兹阿尔比恩岛一个暴露良好的平台顶部部分重建。墨西哥台地边缘El Guay剖面也将分析被解释为撞击成因的增生青金石，将使用阴极发光岩相学(CL)岩石学、元素和同位素地球化学(大宗岩石和微量样品)和定量水-岩石相互作用模型来确定这些碰撞成因沉积物的成因。初步分析发现，在青金石和角砾岩块中有几个明显的CL结晶特征，这将为蒸汽云的沉积机制和地球化学提供重要的新制约因素。将进行测试，以确定全球海水87sr/86sr标准曲线(0.7077至0.7079)通过Kt边界的对称趋势是否可用于确定：(1)原始沉积组分(角砾岩块、青金石、骨骼物质、海相胶结物)的沉积年龄；(2)撞击玻璃的同沉积或早期沉积后事件

9909560FoukeA large-body impact at the Cretaceous-Tertiary (KT) boundary targeted 3 km of carbonate platform covering crystalline basement on the Yucatan peninsula. This study seeks to reconstruct the sediment transport dynamics and geochemistry of the KT impact by analyzing ballistically ejected carbonate sediments deposited close to the Chicxulub crater. The age, source, transport mechanisms, and post-depositional alteration of these deposits will be reconstructed from a well-exposed platform top section at Albion Island, Belize. Accretionary lapilli interpreted to be of impact origin will also be analyzed from the platform margin El Guay section in Mexico, The genesis of these impact-derived sediments will be determined using cathodolumineseence (CL) petrography, elemental and isotopic geochemistry (bulk rock and microsamples), and quantitative water-rock interaction modeling. Preliminary analyses have identified several CL-distinct crystalline features in the lapilli and breccia blocks that will provide important new constraints on vapor cloud sedimentary mechanisms and geochemistry. Tests will be conducted to determine whether symmetrical trends in global seawater 87sr/86 Sr standard curve (0.7077 to 0.7079) through the KT boundary can be used to determine: (1) the depositional age of original sedimentary components (breccia blocks, lapilli, skeletal material, marine cements), and (2) syndepositional or early post-depositional events of impact glass