LE3 .A278 1976

1976

Colwell, John

Acadia University

Master of Science

Masters

Earth and Environmental Science

Earth & Environmental Sciences

The stratigraphy and some petrology of a section of the Windsor Group was studied in considerable detail in a quarter square mile area centered on the Magazine quarry, Little Narrows, Victoria County, N. S. The section lies between the Lower Red Siltstone and the Middle Red Siltstone of Moore and Lewis (1969). It correlates with Bell's (1929) B subzone of the type area at Windsor. The relationship between the chloride and sulphate is considered as well as the relationship between the sulphate. For the Magazine quarry, maps recording chloride in the boreholes drilled for blasting have shown that the sulphate (gypsum or anhydrite) contains trace quantities of chloride in an irregular pattern. An attempt is made to clarify this pattern and the origin of it. Halite (derived from the chloride content) generally makes up less than 0.5 percent of a sample by weight. A sodium sulphate mineral may also be present, however. The evaporite sequence was deposited in a marine envir onment below wave base. Anh ydrite is the oldest sulphate type present but it is n ot known what the original sulphate was. The finely crystalline gypsum was recrystallized from the very finely crystalline gypsum, which formed from the anhydrite. The original sulphate was fine to coarsely laminated to a large degree. The mosaic, the distorted mosaic, the random carbonate and the other textures containing carbonate probably were derived from a laminated texture. The chloride is mostly found in secondary features such as disseminated crystals, cracks and selenite stringers. Occasionally it occurs along the bedding plane with the carbonate laminae in the anhydrite. The chloride occurs most commonly with the anhydrite and least with the finely crystalline gypsum. It more commonly occurs with the random carbonate than with the mosaic texture. A tentative conclusion is that the high chloride~ content is unrelated to the amount of carbonate the sulphate contains, if the carbonate content is less than 20 percent. The chloride and selenite stringers have a very low correlation coefficient when they are treated as independant variable. The irregular distribution of the high chloride rock is only partly explained by the irregular distribution of anhydrite and the recrystallization pattern in the gypsum. A high chloride content occurs at all stratigraphic levels of sulphate occurrence except between the Hazeldale and Cain's Mountain limestones and a five foot interval above the. latter. The conclusions are in general agreement with those of a preliminary study by the author (1974) except for the stratigraphic levels of the halite.

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