What is the correct oldest-to-youngest sequence for a transgressive deposit sequence?

What is the correct oldest-to-youngest sequence for a transgressive deposit sequence?

• A. Sandstone, Limestone, Shale
• B. Limestone, Shale, Sandstone
• C. Shale, Limestone, Sandstone
• D. Shale, Sandstone, Limestone

Answer: (C)

In a transgressive deposit sequence, sea level is rising, so environments shift toward deeper water over time at a given location. Shale forms in deeper, quieter waters, limestone in somewhat shallower open-marine conditions, and sandstone in nearshore, higher-energy settings. Therefore, the oldest sediments will be the deepest-water facies, followed by progressively shallower-water facies as time advances. This gives shale first, then limestone, and finally sandstone as the youngest.

In a transgressive deposit sequence, sea level is rising, so environments shift toward deeper water over time at a given location. Shale forms in deeper, quieter waters, limestone in somewhat shallower open-marine conditions, and sandstone in nearshore, higher-energy settings. Therefore, the oldest sediments will be the deepest-water facies, followed by progressively shallower-water facies as time advances. This gives shale first, then limestone, and finally sandstone as the youngest.