Exercise 1 Solution
Carbonate sediments and rocks are composed of greater than 50 percent carbonate minerals (CO3) and the predominant carbonate mineral is calcium carbonate or limestone (CaCO3) and next dolomite or dolostone (CaMg(CO3)2). Evaporites are considered sedimentary rocks that form when seawater or lake water evaporates and precipitate out minerals; most commonly gypsum (CaSO4.2H2O) and halite (NaCl), plus other minerals depending on the dissolved chemical composition of the source water. Both rock types can dissolve over time when exposed to water. Often carbonates are deposited in a marine environment, thus, it is common for layers of evaporites to be found within carbonate rock sequences. Evaporite rocks dissolve much more rapidly than carbonate rocks and so are found intact above ground in very arid environments or in layers beneath land surface in saline or hypersaline groundwater (brines).