Researchers found fossils of marine organisms in rock layers located high above sea level. What conclusion is best supported?

• A. The area containing the rock layers was previously covered by water
• B. The fossils were transported there by wind
• C. The organisms lived on land
• D. The rocks were formed in a desert climate

Answer: (A)

Fossils of marine organisms in rock layers indicate those sediments formed under seawater. Since the rocks are now far above sea level, the most supported conclusion is that the area was previously covered by water, and later geological processes raised the land (or the sea floor) to its present elevation. The other ideas don’t fit because wind-transported fossils wouldn’t archive a marine environment, desert conditions don’t produce marine fossils, and finding marine fossils clearly points to an aquatic, not terrestrial, origin for those rocks.