Foraminifera fossils show a low delta to the 18th power cap o before 66 million years ago and a sudden rise in delta to the 18th power cap o right after the Chicxulub asteroid impact. Over the next hundred thousand years, the delta to the 18th power cap o values gradually decreased.
Answer
A
The climate before the impact was warm and the climate after the impact was cold but gradually warmed.
B
The climate before the impact was cool and the climate after the impact was warm and gradually got warmer.
C
The climate before the impact was warm and the climate after the impact was cold and gradually cooled.
D
The climate before the impact was cool, and the climate after the impact was warm but gradually cooled.
Explanation
Foraminifera shells generally have higher δ¹⁸O values when water is colder and lower values when it is warmer. The low values before the impact indicate warm conditions; the sudden rise indicates cooling, and the gradual decline afterward indicates gradual warming. Thus, choice A describes the climate sequence.
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