Caspian Sea
The Caspian Sea, like the Black Sea, Namak Lake, and Lake Urmia, is a remnant of the ancient Paratethys Sea. It became landlocked about 5.5 million years ago due to tectonic uplift and a fall in sea level. During warm and dry climatic periods, the landlocked sea almost dried up, depositing evaporitic sediments like halite that were covered by wind-blown deposits and were sealed off as an evaporite sink when cool, wet climates refilled the basin. (Comparable evaporite beds underlie the Mediterranean.) Due to the current inflow of fresh water, the Caspian Sea is a freshwater lake in its northern portions, and is most saline on the Iranian shore, where the catchment basin contributes little flow. Currently, the mean salinity of the Caspian is one third that of Earth's oceans. The Garabogazköl embayment, which dried up when water flow from the main body of the Caspian was blocked in the 1980s but has since been restored, routinely exceeds oceanic salinity by a factor of 10.
Great Salt Lake
The salinity of the lake's main basin, Gilbert Bay, is highly variable and depends on the lake's level; it ranges from 5 to 27% (50 to 270 parts per thousand). For comparison, the average salinity of the world ocean is 3.5% (35 parts per thousand) and 33.7% in the Dead Sea. The ionic composition is similar to seawater, much more so than the Dead Sea's water; compared to the ocean, Great Salt Lake's waters are slightly enriched in potassium and depleted in calcium.