113. 



2.4 Salt deposits are of sedimentary origin and commonly occur in- 

 terbedded with other rocks, such as limestone, dolomite, anhydrite 

 and shale. Under conditions of temperature and pressure present at 

 great depths and during geologic time, bedded salt has flowed along 

 lines of weakness and risen into overlying beds in the form of plugs 

 and domes . 



3. DISTRIBUTION OF SALT IN THE UNITED STATES 



3. 1 The most commercially important deposits of bedded salt are 

 found in New York, Michigan, Ohio and Kansas. They underlie many 

 thousand square miles extending from the outcrop downward to depths 

 of more than 5,000 feet. Figure 1 shows the location of the principal 

 deposits of rock salt in the United States. 



3.2 In New York , the salt occurs in the Salina formation of Silurian 

 age.' ' It crops out along a band extending from the Mohawk Valley 

 on the east to the Niagara River on the West. The salt is not present 



at the outcrop because it has been dissolved. The Salina beds dip south- 

 ward at a low angle. The dip is variable, averaging from 50 to 100 

 feet per mile, depending on the local structural conditions. At its 

 maximum, the Salina is about 1,000 feet in thickness. The salt may 

 be present in several beds. Its total thickness is more than 300 feet 

 in central New York, south of Syracuse. In the western part of the 

 state, the salt becomes thinner and may be absent in the Buffalo area. 

 It continues southward under the increasing thickness of younger beds 

 into southern New York and northern Pennsylvania, where the thickness 

 of salt is over 600 feet in some deep wells. The total area in New York 

 underlain by salt is roughly 10,000 square miles, as shown on Figure 2. 



3.3 The entire northwestern part of Pennsylvania is underlain by the 

 Salina formation and salt has been found in many wells drilled for oil 

 and gas.'"' Throughout most of the area the aggregate thickness of 

 the salt beds is at least 50 feet. In half the area the aggregate thick- 

 ness is over 100 feet and the aggregate thickness reaches a maximum 

 of over 500 feet. The salt beds are found at depths of from 1500 feet 

 in northwestern Pennsylvania to more than 8000 feet in the deepest 

 part of the syncline. Figure 3 shows the area in Pennsylvania under- 

 lain by salt and the depth below sea level of the top of the salt. 



3.4 The salina beds continue westward into eastern Ohio and underlie 

 about one-third of the state. ^> ( 8 ) The salt occurs in beds of Silurian 

 age, which probably represent the westward extension of the Salina for- 

 mation of New York and Pennsylvania. This horizon is below the surface 



