Existing comment:
Sedimentary rocks of this age in other parts of the world contain similar patterns -- the presence of iridium followed by a sudden drop in plant diversity and a predominance of ferns.
Hypothesis: As asteroid, perhaps six miles wide, slammed into Earth 65 million years ago. Many ecosystems collapsed and ferns took over on land, for a time. After the impact, life endured, but it would never be the same again. |