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

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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.