Environmental effects of the impact of a meteorite 66.4 million years ago may have led to the extinction of many species on earth. which evidence best supports this theory?

The impact of the meteorite marks what is known as the Cretaceous-Tertiary or K-T boundary. Geologists across the world have noted a thin layer of soil that marks this boundary. It is rich in Iridium, an element that is extremely rare on earth but very common in meteorites. The layer was formed as the vaporized material from the impact dispersed in the atmosphere and was eventually deposited across the globe.  

Reduction in overall biodiversity