The asteroid that killed the dinosaurs was initially discovered by Glen Penfield in the 1970’s while he was searching for oil in the area. It wasn’t until he joined with Alan Hildebrand that he was able to confirm Chicxulub as an impact crater. The evidence that he finally submitted for approval included: shocked quartz, tektites, and a magnetic anomaly in the area. Isotope analysis is what was used to date the surrounding rocks. The crater is also surrounded by a ring of sinkholes. That is an unusual attribute for a crater. It has been proposed that the formation of the Yucatan crater Cenote ring, a ring of sink holes important for Yucatan water resources, may be linked to the Chicxulub structure by slumping at the crater rim or solution collapse within impact deposits. Chicxulub is certainly one of the largest impact structure on Earth and if the 300 km size estimate is proven correct, perhaps one of the largest produced in the inner solar system in the last 4 billion years.
The asteroid that killed the dinosaurs would have killed them in several waves. The first one would have been the initial impact and the resulting tsunami. The next wave would have been acid rain and fires that would have destroyed the plant life. The third wave would have been the herbivores, followed by the meat eaters, then finally the the carrion eaters would have died of starvation. Eventually 90% of the life within thousands of miles would have been dead.
The American Geophysics Union wrote a great in depth article on the asteroid that killed the dinosaurs. Here on Universe Today there are several articles on the asteroids and the Chicxulub Crater. Astronomy Cast has a good episode on asteroids as bad neighbors.