The theory of a meteorite hitting the earth nearby is the only thing that makes sense.
Swinburne and her colleagues speculate the a meteorite 10 km wide slammed into the earth, causing an explosion 10000 tines as powerful as would be caused by the world arsenal of nuclear weapons, leaving a crater off the coast of the Yucatan peninsula 190 km in diameter.
The explosion, they think, spewed massive debris and created a fireball of incandescent gas, altering earth's climate and resulting in the death of more than half of the world's plants and animals.