NPS photo. The fossil resources preserved in Glacier give a glimpse into the beginning of life on our planet and help to tell the deep history of the park. Stromatolites aren't the only fossil present in Glacier, but they are the most commonly found. There are many others in the park that span the geologic record and are far less evident in terms of location, quantity, or size. Older sediments contain Horodyskia monilifomis, a multicellular organism resembling a string of beads and considered by some researcher to be an important evolutionary link to eukaryotic life, which includes plants, animals, and fungi. Cretaceous period sediments include mollusks, bivalves, gastropods, and plants. Rocks from the Paleogene and early Neogene periods contains petrified wood and fossilized gastropods, mammals, fish, insects, mollusks, and plants.
In Glacier, paleontology hasn't been the main focus of geological research—there is still a lot to learn. While the fossilized microorganisms, small mammals, and insects may lack the glamour of dinosaurs, there is no question these fossils are important to the development and understanding of all life as we know it today. The ancient Belt Sea covered parts of present-day eastern Washington, northern Idaho, western Montana, and nearby areas in Canada. This includes the area now known as Glacier National Park. Blue-green algae, or cyanobacteria, thrived in shallow parts of the Belt Sea and played a significant role in the formation of the carbonate rocks of the park. Limestone and dolomite are examples of the carbonate rocks that are found today. Stromatolites are the remains of these cyanobacteria.
Starting as a small clump of blue-green algae, stromatolites grow by catching sediments moving in the water around them. With each new layer of sediment, grows a new layer of algae trapping the sediment in between. Repeated over and over, this expands the mat of algae until it resembles a column or cone. Today, these fossils can take on various shapes and sizes, but often resemble sliced cabbage, the cross-section of a jawbreaker, or swirls of water.
As some of the earliest forms of photosynthetic life, stromatolites began to change the world around them. Sunlight allows algae to consume carbon dioxide from seawater and release oxygen in the process. There are two important results from this process:
Glacier's rocks are either very old or relatively young. Precambrian, Cretaceous, and Tertiary age rocks are exposed within the park, along with the much younger Quaternary sediments. Missing from the park is an incredible gap of time—over 800 million years! The compression and uplift that built the Rocky Mountains caused a huge fault, known as the Lewis overthrust. This movement pushed older rocks up and over the top of younger ones. Consequently, the Paleozoic geological era, with its spectacular trilobites, mollusks, giant ferns, and dinosaurs, has been eroded from the upper layers of Glacier's rocks, or is buried far below a two-mile-thick slab of very old Precambrian rock that is exposed. Learn more about Glacier's fossils
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Last updated: September 17, 2024