 Iridium, magnetic minerals, microspherules, carbon, and nanodiamonds are all subject to differing interpretations as to their nature and origin, and may be explained in many cases by purely terrestrial or non-catastrophic factors.There is evidence that the megafaunal extinctions that occurred across northern Eurasia, North America, and South America at the end of the Pleistocene were not synchronous.The extinctions in South America appear to have occurred at least 400 years after the extinctions in North America.