ABSTRACT

The Cambrian section in the subsurface of southern Alberta is composed of quartzarenite, glauconitic sandstone, shale, limestone, and dolomite. These facies were deposited in environments ranging from supratidal to subtidal.

Both clastic and carbonate rocks were subjected to the same diagenetic and burial history. Diagenesis occurred in the shallow phreatic, marine phreatic, mixing, and deep-burial zones.

Blocky calcite cement and syntaxial rims around echinoderm fragments were precipitated in the carbonates in the fresh water zone. Precipitation of hematite and dissolution of K-feldspars occurred in the sandstone in this zone. Fibrous calcite cement formed in the carbonate in the marine-phreatic zone.

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Mixing of fresh and marine formation waters at shallow burial depths resulted in a large number of diagenetic products in both carbonate and clastic rocks; e.g., dolomitization of limestone, and the precipitation of illite, kaolinite, authigenic K-feldspars, quartz overgrowths, and carbonate cements in the sandstone.

Ferroan dolomite formed either under reducing conditions or in response to a high sedimentation rate. Consequently, ferroan dolomite is more abundant in dolomites that have been subjected to deep burial and in dolomite-cemented sandstones. At deep burial depths, mixing of upward-moving hydrothermal fluids with marine formation water resulted in the formation of ferroan and saddle dolomites. Chlorite formed in the sandstones in the deep-burial zone when Fe⁺⁺ was available for diagenetic reactions.

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