| OCR Text |
Show 14 are probably poorly consolidated silts tones, sandstones, conglomerates, limestones, and volcanic ash beds. The Pleistocene sediments are more than 650 feet thick ( Eardley and Gvosdetsky, 1960) and consist largely of sands, silts, clays, soils and oolitic sand. Deposits of mirabilite, or glaubers' salt ( NaoSOA . lOH^ O), are Pleistocene deposits of special interest. There are several deposits under one to three feet of sand along the western portions of the southern shore of the Great Salt Lake. One of the Lake's deposits of sodium sulphate starts near the site of the Saltair resort and extends west to a point near Silver Sands Beach, underlying approximately 1780 acres. A second deposit begins about three miles from the east boundary and parallels the shore for approximately one and one- half miles to the southwest, underlying 1762 acres. The layers of sand, silt and sodium sulphate contain 12.4 percent sodium sulphate ( standard deviation 4.7) on a wet basis ( average 15.5 percent moisture), and 17.2 percent sodium sulphate ( standard deviation 7.1) on a dry basis. Thus, each deposit contains approximately one- half million tons of anhydrous sodium sulphate. ( Wilson and Wideman, 1957) Eardley ( 1960) describes one bed of relatively pure mirabilite which lies 15- 25 feet below the floor of Great Salt Lake, extending 9.5 miles from a point about one mile west of Promontory Point to slightly beyond mid- Lake. It starts as a feather edge on the west and gradually increases in thickness eastward for six miles to 15 feet thick. In the next mile it thickens to 32 feet, its maximum thickness. This mirabilite bed, which serves as the foundation of the Southern Pacific causeway, may have been deposited against a fault scarp on the east side ( Eardley, 1962). |
