Final answer:
Calcium and bicarbonate ions combine in the sea to form carbonate rocks like limestone and dolomite.
Step-by-step explanation:
Calcium and bicarbonate ions combine in the sea to form carbonate rocks like limestone and dolomite. This reaction occurs when calcium ions (Ca2+) in seawater react with bicarbonate ions (HCO3-) to produce calcium carbonate (CaCO3). The calcium carbonate eventually forms sediment on the ocean floor, which over geologic time, forms limestone and dolomite.