Precambrian carbonate rocks of the Siyeh Formation are described from a section located near the north boundary of Waterton Park, southwestern Alberta.

Mottling is common in the Siyeh carbonates and is related to several types of sedimentary structures, all of which are diagenetic in origin and are attributed to processes of soft sediment slumping and fracture development in addition to authigenic cementation.

The Siyeh sediments were derived from a low-lying source area southeast of the site of deposition. The source rocks were fine-grained, low-grade metamorphic schists and phyllites composed largely of quartz and fine-grained micaceous minerals. Some granites may have been present.

Deposition of the clastic constituents was followed by extensive diagenetic calcitization, which the present study indicates may have been responsible for most if not all of the calcite in the Siyeh rocks. Late diagenetic dolomitization, affecting all beds to some degree, represents the last major phase of mineralization in the Siyeh sediments.

The presence of algae, oolites, and graded bedding indicates that the Siyeh sediments accumulated in a shallow sea, similar to the Recent Shark Bay marine lagoon of Western Australia.

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