Question

1. the cessation of banded iron formations in the geologic record indicates the emergence of ______ in earths atmosphere

hydrogen
carbon dioxide
oxygen
helium

Explanation:

Banded iron formations formed in an oxygen - poor environment. When oxygen levels in the atmosphere increased, iron in the oceans reacted with oxygen to form insoluble iron oxides, which stopped the formation of banded iron formations.

Answer:

C. Oxygen