Redbeds are hematite layers between layers of rock. they can indicate the
presence of which element in the atmosphere?

Redbeds indicate the presence o iron in the environment. Red beds are red sedimentary rocks and the color is due to the presence of the ferric oxides. Ferric oxides occur as a coating on the sedimentary grains. In between the shale and cherts, iron-rich sediments can be found. 

Explanation:

answer(c) carved on a babylonian clay tablet that showed earth as a flat circular disk;