Question

Which of the following would cast doubt on the asteroid-impact hypothesis for the extinction of the dinosaurs?

A. determining that birds are descended from extinct dinosaurs
B. finding a crater and associated iridium layer that are 200 million years old
C. finding abundant fossil dinosaur bones in strata above (younger than) the 65-million-year-old iridium layer
D. finding abundant fossil dinosaur bones in strata below (older than) the 65-million-year-old iridium layer

Answer 1

Finding abundant fossil dinosaur bones in strata above (younger than) the 65-million-year-old iridium layer would cast doubt on the asteroid-impact hypothesis for the extinction of dinosaurs, suggesting they survived past the event believed to have caused their extinction. Option C.

Step-by-step explanation:

The asteroid-impact hypothesis suggests that a large asteroid impact caused the extinction of the dinosaurs about 65 million years ago. This hypothesis is supported by a global iridium-rich layer and the Chicxulub crater in the Yucatán Peninsula, which corresponds to the end-Cretaceous period.

If we were to find abundant fossil dinosaur bones in strata that are younger than the 65-million-year-old iridium layer, it would cast doubt on the asteroid-impact hypothesis because it would suggest that dinosaurs survived for a time after the asteroid impact event that is believed to have caused their extinction.

However, finding fossils in lower strata (older) would not be surprising, as it would mean these dinosaurs existed before the event. So option C.