Luther — Geology of the Salt District 



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all of which is hard drilling ; and the passage through the flint is a distinct 

 epocli in the history of every well. 



As the black shales that overlie the Onondaga limestones are very soft, 

 and offered but slight resistance to denuding glacial forces, the upper surface 

 of the limestone along the crest of the Helderberg escarpment is uncovered in 

 many places disclosing glacial scratches and polishmgs. 



The movements that gave to the strata of the whole salt district a 

 pronounced dip to the south and produced gentle undulations in many parts, 

 fractured and dislocated the rigid Onondaga limestones, causing many small 

 faultiners and numerous fissures. Some of the latter that were so located as to 

 receive the waters of some depression of the surface, have been so enlarged by 

 the solvent action of the water on the limestone, that streams of considerable 

 size disappear into them. Such sink holes occur for the entire length and 

 breadth of the outcrop. 



The disturbance of the strata is especially noticeable in the exposures of 

 the rocks along the sides of the Onondaga valley and the adjacent country south 

 of the Onondaga Salt Springs. 



The foldings and fractures are on too extensive a scale to allow belief in 

 a superficial orgin, and the dikes of kimberlite exposed on Green street hill in 

 the city of Syracuse, two or three miles north of the escarpment and in an 

 horizon that is below the gypsum beds, furnish abundant evidence that not all 

 of the disturbance of the limestones can be due to crystallization in the gypsum 

 beds or dissolution of the rock salt beds, and that the cause and effect of the 

 movements were much deeper seated. 



It is doubtless through these fissures that the waters of the higher land 

 in the south part of the count}' find access to the rock salt and become jwtially 

 saturated. 



In the soft, clayey, red shales beneath the salt beds the fissures would be 

 likely to close up, and the brine, under pressure from above, must follow the 

 upward inclination of the strata until an outlet was found north in the basin 

 of Onondaga lake. 



It is not impossible that the brine springs of the Medina sandstones also 

 derive their salt from the great Salina beds. The brine may find its way 

 down through the Salina, Niagara and Clinton beds by means of the fissures, 

 and thence upward through the porous layers of coarse sandstone to the 

 surface several miles north of the north edge of the salt beds. 



Between Caledonia and Le Roy, where the Onondaga limestone is the 

 surface rock, there are many long, low, folds usually not more than two or 



