Question

What marks the end of the dinosaurs in the fossil record?

The iridium anomaly layer
The rise of flowering plants
The appearance of mammals
A sudden increase in sea levels

Answer 1

The event that marks the end of the dinosaurs in the fossil record is primarily characterized by **the iridium anomaly layer**. This layer, found in sedimentary rocks at the Cretaceous-Paleogene (K-Pg) boundary, is associated with a mass extinction event that occurred approximately 66 million years ago, believed to be caused by a massive asteroid impact. The high levels of iridium, which is rare on Earth but more common in asteroids, point to this catastrophic event that led to the extinction of roughly 75% of Earth's species, including all non-avian dinosaurs.