Abstract

The diagenetic history is deduced from a comparison between the mineralogy, porosity, crystal-size, and microfacies of Recent carbonate sediments and the corresponding properties of the Wettersteinkalk. The stable diagenetic carbonate phases are low-Mg calcite and dolomite. Dolomitization (on an average 30 percent dolomite in the rocks studied) for the most part occurred very early in the diagenetic history and was favored by near mean sea level conditions. Initial high porosity was reduced to 1 percent by cementation. Granular and fibrous cements can be distinguished in the Wettersteinkalk. Reduction of porosity and lithification must have been early diagenetic processes; no secondary porosity was developed. Cumulative frequency curves of crystal-sizes do not plot as straight lines and are therefore non-normal distributions; they are markedly skewed or show a zigzag pattern, hence the Wettersteinkalk crystals are not fully adjusted to their diagenetic environment. Crystal-enlargement by means of solution alteration was the major neomorphic process; more than 70 percent of all measured crystals are beyond the 10mu limit. Crystal boundaries in the granular and fibrous neomorphic mosaics and in the cements are typical of strained carbonate crystals. Diagenesis of the Wettersteinkalk can be subdivided into four characteristic stages on the basis of the thickness of the overlying rock column. On an average about 70 percent of the minerals and crystals of the Wettersteinkalk are the products of diagenesis. Rareness of fossils and sedimentary ore fabrics in these rocks testifies to the high degree of diagenesis which has resulted from tectonic stress and from deep burial to an estimated depth of 3000-4000 meters.

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