A high ? 18oxygen/16oxygen ratio in the shells of marine animals indicates __________.
A) colder temperatures and lower sea levels
B) higher temperatures and lower sea levels
C) colder temperature sand higher sea levels
D) warmer temperatures and higher sea levels

Question

Quizplus · Accepted Answer

A high 18oxygen/16oxygen ratio in the shells of marine animals is a proxy for colder temperatures, as more 18oxygen is incorporated into the shells when temperatures are lower. This ratio is also consistent with lower sea levels, as colder temperatures are associated with the growth of continental ice sheets, which remove water from the oceans and cause sea levels to drop. Therefore, choice A is the best answer.

A High ? 18oxygen/16oxygen Ratio in the Shells of Marine