Petrographic Examination of Dolomitization, Miette Carbonate Complex, Jasper Park, Alberta.

Abstract

<p>Upper Devonian carbonate complexes show varying degrees of dolomitization throughout Alberta. The Miette complex of Jasper Park contains penecontemporaneous dolomite in several forms within platform and biostromal formations. Isolated dolomite euhedra selectively replace more permeable cement fabrics; less permeable micrite muds, intraclasts and globular stromatoporoids are not extensively dolomitized. Amphipora-rich beds and brecciated reef margin biostromes are almost totally replaced by dolomite, presumably because of their initial high porosity. Small-scale dolomite fronts have not selectively replaced host rocks; they occur in micrite, calcite spar and chert. Repeated penecontemporaneous mixing of fresh and salt water in the phreatic zone is the suggested mechanism for dolomitization. Fluctuations in sea level are inferred from cement fabrics, erosion surfaces and intertidal facies, detrital dolomite beds, and a general stratigraphic sequence of growth and extinction of organic banks and biostromes. Later diagenetic dolomite is present in veins and vug fillings.</p>