112 NEW YORK STATE MUSEUM -^ 



mercial samples an average of 80i/4^ of lime sulfate with 14^ 

 of earthy matter, 5^ of lime and magnesian carbonates, and, quite 

 significantly, .6fo of lime phosphate and organic matter, these last 

 ingredients suggesting an organic origin, while the residual lime 

 and magnesia point to the probable original condition of the de- 

 posit. It may be added in this connection that in the limestone 

 no. 1, in close proximity to one of the fossil localities and nearly 

 at the same level^ occurs a small isolated mass of decomposed 

 gypsum, possibly 10 cubic feet in dimensions, which is due appar- 

 ently to the agency of a small sulfurous percolation now extinct. 

 I believe, therefore, that the structure of the great gypsum de- 

 posits of Cayuga county separates them sharply from those exist- 

 ing elsewhere in New York in the strata of the Salina period; 

 and that their associations with limestones, both below and above 

 them, containing fossils of the lower divisions of the Lower 

 Helderberg, as well as the nearly uniform character of the rock 

 series from the lake level to the Oriskany sandstone, indicate for 

 them a place in the lower portion of the Lower Helderberg in 

 which I include the Waterlime group.^ 



Professor Williams's deductions in regard to the geologic posi- 

 tion of the gypsum at Union Springs are apparently well 

 grounded, but it seems that there is some difference of opinion as 

 to where a geologic period begins. Apparently, Mr Williams 

 considers the Lower Helderberg formation as beginning where 

 the first fossils which are typical of these deposits made their 

 appearance. If this ground be accepted, it will be necessary to 

 refer the deposit at Union Springs to the Lower Helderberg. 

 The general opinion of geologists, however, seems to be that 

 the gypsum deposits of the State belong with the Salina group, 

 and Dr J. M, Clarke has recently assigned the Tentaculite lime- 

 stone to the Salina rather than to the Lower Helderberg, where 

 it has been included for many years. In Luther's section of 

 the Livonia salt shaft, the upper gypsum bed is referred to the 

 Lower Helderberg. The lower and thicker deposits are referred 

 to the Salina period; but, in view of the more recent opinion of 

 Dr Clarke concerning the Tentaculite limestone, it is very likely 

 that the upper gypsum bed at Livonia would also be referred to 



^Williams, S. G. Geological Relations of the Gypsum Deposits in Cayuga 

 County, N. Y. Am. Jour. Sci. September 1885. 



