Nature
The Appekunny Formation is a thick sequence of Proterozoic rock strata in Glacier National Park’s Lewis Range, especially visible on Singleshot Mountain near St. Mary. Composed mainly of mudstone and siltstone deposited in a shallow sea, it is about 1.2 to 1.4 billion years old and averages roughly 1,970 feet in thickness. Named for Apikuni Mountain, it stands out not only as a major feature of the park’s landscape but also for bedding structures that may preserve Horodyskia moniliformis, a form interpreted as possibly the oldest known metazoan on Earth. This gives the formation importance for both deep geologic history and the study of early life.
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Montana · United States
