What is the significance of the specific ratio of carbon isotopes (¹³C:¹²C) in microfossils found in Australian sediments that are 3.5 billion years old? A) The ratio occurs only where photosynthesis has occurred. B) The ratio is a method for confirming the geological age of the rocks. C) Carbon occurs only in fossils of living organisms. D) The ratio occurs only in meteorites from extraterrestrial sources. E) The ratio indicates there were hydrothermal vents in the region 3.5 billion years ago.

Question

Quizplus · Accepted Answer

The specific ratio of carbon isotopes found in microfossils from Australian sediments that are 3.5 billion years old indicates that photosynthesis had occurred in the region at that time. This is because photosynthesis produces a distinctive ratio of carbon isotopes, with a higher concentration of the lighter isotope carbon-12. Therefore, option A is correct. The other options are incorrect as they do not relate to the actual significance of the specific carbon isotope ratio in microfossils.

What Is the Significance of the Specific Ratio of Carbon