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

Question

Sudden increase in sea levels
The rise of flowering plants
The appearance of mammals
The iridium layer

Answer 1

The end of the dinosaurs in the fossil record is primarily marked by the presence of the iridium layer. This layer is associated with the Chicxulub impact event, which is believed to have caused a mass extinction around 66 million years ago, leading to the disappearance of the dinosaurs. The other options listed, such as the sudden increase in sea levels, the rise of flowering plants, and the appearance of mammals, occurred in different contexts and are not direct markers for the end of the dinosaurs.