Appekunny Formation, Geological formation in Glacier National Park, Montana, United States.
The Appekunny Formation is a geological layer in Glacier National Park made up of gray, black, and greenish argillite with thin, distinct bedding patterns. These rock layers spread across the Lewis Range and show clear changes in their composition throughout.
This formation took shape about 1.4 billion years ago when this area sat under a shallow ancient sea that slowly deposited layers of sediment. Geologist Bailey Willis first documented and named these rock layers in 1902 while surveying the Lewis and Livingston Ranges.
Scientists and geologists travel to this formation to study ancient sedimentary structures that provide evidence of early multicellular life forms.
The formation is most visible along Going-to-the-Sun Road and on the lower section of Grinnell Glacier Trail. Early morning or late afternoon light works best to see the different colors and layering patterns clearly.
You can still spot ancient mud cracks and ripple marks in the formation that were pressed into the seafloor about 1.4 billion years ago during tidal movements. These old marks are like footprints left by waves and water level changes from that distant time.
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