Carbonate Compensation Depth (CCD) is the depth at which which process balance occurs?

• A. Depth where calcium carbonate sedimentation exceeds dissolution
• B. Depth where calcium carbonate sedimentation equals dissolution
• C. Depth where calcium carbonate sedimentation is less than dissolution
• D. Depth where there is no carbonate deposition

Answer: (B)

The depth at which calcium carbonate sedimentation equals dissolution. At this level, the rate of CaCO3 being deposited by shells and sediments matches the rate at which it is dissolving into seawater, so there is no net gain or loss of carbonate material. Above this depth, sedimentation dominates and carbonate sediments can accumulate; below it, dissolution dominates and carbonate materials tend to dissolve, limiting preservation. The exact depth varies by location and ocean chemistry, but the idea is that the CCD marks where the two processes balance.