Page:The Eurypterida of New York Volume 1.pdf/113

 salt. Recent writers have held that such thicknesses of salt can not be explained by the desiccation of a sea enclosed by land barriers in distinction from bars. The salt of the Retsof mine would require the desiccation of a sea 1750 feet deep, and this is irreconcilable with the shallow water conditions of the Salina beds evidenced by the frequent sun cracks in the dolomites and waterlimes of the formation.

There is no doubt that the culminant salt pan condition of the Salina period with its heavy precipitation of salt, implies an arid climate. There is also evidence indicating the persistence of these desert conditions throughout the Salina period and at the time when the eurypterid-bearing sediments were deposited. This evidence is found in (1) the scarcity of carbonaceous matter in the Salina beds, (2) the prevalence of dolomites and waterlimes.

The Salina beds are notably free from carbonaceous matter when compared with the underlying Niagaran and overlying Helderbergian beds. This may be partly due to the absence of such decaying marine organisms as furnished the bitumen with which part of the underlying Guelph dolomite is saturated, but it is also an indication of the absence of vegetation on the adjoining land. This becomes especially manifest if it is considered that the Salina sea was almost entirely surrounded by land, and that, as the frequent sun cracks in the waterlimes of central New York demonstrate, the shore was nowhere very distant. Several authors, as