An international team of researchers found a substance known as melt glass, which forms at temperatures of 1,7000 to 2,200 degrees Celsius and can result from a "cosmic body" hitting the earth.
The researchers believe the huge cosmic impact triggered a vicious cold snap, which caused widespread destruction.
The material was unearthed in a thin layer of rock in Pennsylvania and South Carolina in the US and in Syria.
Tests confirmed the material was not of cosmic, volcanic or human-made origin.
"The extreme temperatures required are equal to those of an atomic bomb blast, high enough to make sand melt and boil," James Kennett, professor of earth science at UC Santa Barbara, was quoted as saying by the Daily Mail.
The melt-glass seems identical to other material found in Meteor Crater in Arizona, and the Australasian tektite field, and also matches melt-glass produced by the 1945 Trinity nuclear airburst in New Mexico in the US, Prof Kennett said.
The team's findings, published in the Proceedings of the National Academy of Sciences, support the controversial theory that an asteroid impact some 12,900 years ago triggered the start of an unusual cold period on Earth, leading to the mass extinction of human and animal life.
In the cold period, known as the Younger Dryas, North American megafauna including mammoths and giant ground sloths disappeared forever, along with a prehistoric civilisation called the Clovis people who are regarded as the first human inhabitants of the New World. (More)