The contrast between the salt section exposed in mines at Retsof, New York, and Detroit, Michigan, can be explained by differences in the environment of deposition. Where local recrystallization has occurred, primary bedding or laminations have not necessarily been destroyed; the major changes are enlargement of grains, the expulsion of insolubles from within crystals, and the consequent destruction of primary crystal structure. Primary features dominate both sequences.

Alling and Briggs (1961) presented evidence of water depth of more than 300 ft 25 mi inside the fringing Niagaran reefs of the Michigan basin. Throughout the Detroit mine, laminations are uniformly spaced, a feature documented by Richter-Bernburg (1953) and others as characteristic of deep-water deposition. Deposition apparently was at a depth sufficiently great to prevent the disturbance of primary bedding structure by turbulence in the basin water.

In contrast to the typical "normal" anhydrite-dolomite laminae (Jahresringe) exposed in the Detroit mine, bedding in the Retsof, New York, mine is expressed as contrasting bands of light and dark, uniformly sized halite crystals through which insoluble material is diffused. Contrast in bands is a function of insoluble content, the separation being gradational rather than abrupt. Primary structures offer additional substantiating evidence of shallow-water deposition in New York.

The differences in physical characteristics of the salt point to less turbulence (greater water depth) in the Michigan segment of the Salina evaporite basin. Increased turbulence and consequently bottom disturbance not only would have disrupted primary bedding features but also would have destroyed or prevented the development of density stratification in the basin waters.

Although the problem of defining depth in absolute terms may remain, characteristic features can be identified for "deep" and "shallow" environments of halite deposition. It seems more appropriate to consider bedded salt as a normal marine sediment than as a "chemical freak."

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