Page:The Eurypterida of New York Volume 1.pdf/112

 The oft repeated alternation of gypseous beds with shales or limestone is illustrated by the section at Buffalo, where five to six repetitions of gypsum and shale are exposed. A like repetition of gypsum beds, the gypsum mostly in thin seams and nodular layers, is shown in the section of the Livonia salt shaft, Livingston county, N. Y. This alternation of the gypseous beds with the dolomites and shales indicates a constant change of conditions which is difficult of explanation in a slowly and regularly desiccating basin, but denotes a periodic interruption of the drying process, either by inflow over the bar, or, perhaps, by seasonal freshets.

Another feature of the Salina beds favoring the bar theory is the great thickness of the salt beds. In the Retsof salt shaft at York, Livingston co., [Luther, op. cit. p. 118] the drill passed successively through 22 feet of salt, 30 feet of shale and limestone and again through 58 feet of