The Belt Supergroup
Twenty kilometres of sediment accumulate in a basin that becomes Glacier National Park.
- When
- Known to
- ± 30 million years
- Era
- Mesoproterozoic, Proterozoic
Between about 1.47 and 1.4 billion years ago, an immense thickness of mud, sand and carbonate is laid down in western North America. Because the rocks were never strongly metamorphosed, they preserve ripple marks, mudcracks and stromatolites in extraordinary detail, along with some of the era's best microfossils. The peaks of Glacier National Park are carved from them.