Which fossils provide information as to the mode of formation of an oxygen-rich atmosphere by about 2 billion years ago?
A) stromatolites
B) trilobites
C) dinosaurs

Question

Quizplus · Accepted Answer

Stromatolites are layered bio-chemical accretionary structures formed in shallow water by the trapping, binding, and cementation of sedimentary grains by biofilms of microorganisms, especially cyanobacteria. These organisms are thought to have been crucial in the development of the Earth's oxygen-rich atmosphere around 2.4 to 2.3 billion years ago during the Great Oxygenation Event.

Which Fossils Provide Information as to the Mode of Formation