Abstract

The Great Salt Lake is the largest saline lake in North America. It occupies the lowest area in a drainage basin of 57,350 sq km. The basin holds a sedimentary sequence at least 4,500 m thick that accumulated through much of Tertiary and Recent time. Lake brines are of the Na-(Mg)-Cl and Na-(Mg)-Cl-(SO₄) types (Eugster and Hardie, 1978). High carbonate content characterizes the sediments.

Oolite and algal mounds are major sediments along the western shorelines and oolite extends in places in shallow water well out into the lake. Much of the oolite from Great Salt Lake is similar or identical to much oolite in limestone and dolomite in ancient rocks. The abundant fecal pellets and brine shrimp egg capsules also reflect the high carbonate content. Gypsum occurs around the lake shores in fine-grained sediments. Gypsum also occurs within the lake in canals or cores from the lake bottom fine-grained sediments. Halite is precipitated on the lake bottom, but goes into solution when the lake level rises. During the winter mirabilite (Na₂SO₄−10 H₂0) precipitates, but dissolves during the spring and summer. Mirabilite beds occur beneath sand and fine-grained sediments in cores. Finegrained sediment (silt, clay, mud) with large amounts of CaO and MgO is widely distributed over the lake bottom. If lithified many of these sediments would be silty or clayey carbonate rocks. Similarly, sand samples contain large amounts of CaO and MgO.