A study for the long-term and short-term disturbances of the envirnment by the extraterrestrial impact at the Cretaceous/Tertiary boundary

我们在古巴Fomento地区和墨西哥Lajilla地区白垩纪/第三纪（K/T）边界的撞击地点附近进行了实地调查，以调查撞击引发的海啸的强度和持续时间。结果，我们发现在Fomento地区观测到了向陨石坑方向的第一次海啸波的证据，以及希克苏鲁伯陨石坑内外的撞击。这些观测结果支持了海啸是由海水侵入火山口并从火山口溢出而产生的假设。我们还研究了古巴中部、墨西哥和新西兰的K/T边界沉积物及其邻近沉积物，以几千年的分辨率研究撞击后100万年内环境的长期扰动。在K/T边界上方，n-C_<31>/(n-C_<29>+n-C_<31>)比值和δ^<13>C_<wax>显著降低。此外，n-C_<31>/(n-C_<29>+n-C_<31>)比值和δ^<13>C_<蜡>的分布随年龄变化而变化。特别是在古新世早期，这些值呈正相关，表明陆生植物中记录了碳循环扰动和环境变化。我们进一步研究了墨西哥Lajilla的K/T边界矿床，并与撞击后70 ka的古巴矿床进行了对比。在新西兰，我们获得了富含铱的粘土层。基于对古巴、墨西哥和新西兰的研究，我们可以讨论K/T边界撞击后100 ka内的古环境变化。

We conducted field survey near the impact site at the Cretaceous/Tertiary (K/T) boundary at Fomento area, Cuba and Lajilla area, Mexico in order to investigate the magnitude and duration of the impact-induced tsunami. As a result, we found that the evidence of the crater-ward first tsunami wave is observed at Fomento area as well as the impactite in and out of the Chicxulub crater. These observations support the hypothesis that the tsunami was generated by the ocean water invasion into the crater and overflow from the crater.We also studied K/T boundary deposits and their adjacent deposits in central Cuba, Mexico, and New Zealand in order to study the long-term disturbance of the environment within one million years after the impact with a resolution of several thousand years. We found that n-C_<31>/(n-C_<29>+n-C_<31>) ratio and δ^<13>C_<wax> remarkably decreased just above the K/T boundary. In addition, the distributions of n-C_<31>/(n-C_<29>+n-C_<31>) ratio and δ^<13>C_<wax> were variable age by age. Especially, these values had positive correlation during early Paleocene, suggesting that carbon cycle disturbance and environmental change by the impact was recorded in terrestrial plants. We further studied the K/T boundary deposit at Lajilla, Mexico and correlated with Cuban deposits until 70 ka after the impact. In New Zealand, we obtained iridium-rich clay layer. Based on our study at Cuba, Mexico, and New Zealand, we could discuss the paleo-environmental change within 100 ka after the K/T boundary impact.