What Happened To The Western Interior Seaway?

What Happened To The Western Interior Seaway

What caused the disappearance of the Western Interior Seaway?

The Western Interior Seaway’s genesis – The old Farallon and Kula tectonic plates were subducting beneath the North American Plate during the Cretaceous epoch. This resulted in the deformation of the ground above, forming a massive back-arc basin. During a series of incursions (or sea-level rises) during the Cretaceous, the basin began to fill with ocean water.

Thus, the Western Interior Seaway was created. In conjunction with the aforementioned plates’ subduction, they suffered partial melting. Multiple strata of ash layers (or bentonites) are preserved today as evidence of volcanic activity caused by the upwelling of ice melt at the edge of the sea. These datable ash layers can be utilized for stratigraphic correlation (or matching rocks of the same age) across the WIS.

Reconstruction of tectonic plate interactions at the period of the Western Interior Seaway in western North America. Further tectonic activity resulted in several sea-level variations in the WIS. At the end of the Cretaceous, the seaway ceased to exist as a result of regional uplift and mountain formation on the western side of North America.

During the Late Cretaceous, when dinosaurs roamed, the Western Interior Seaway would have covered the Badlands. However, there are no dinosaur fossils in the rocks of Badlands National Park. Because they were unable to swim into the Western Interior Seaway, their bones were not fossilized here.

Instead, marine fossils from this time period, including mosasaurs, ammonites, and baculites, have been discovered in the Badlands. Oceans of Kansas, Indiana University Press, 2017. Everhart, Michael J. Updated on 10 November 2020: The Mosasaur was the dominant predator of the Western Interior Seaway (U.S.

National Park Service)

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When did Montana become a sea?

Today’s winter storm warning from the National Weather Service prompted me to recall some study I conducted on Montana’s tropical history. Therefore, prepare a cup of anything warm, arrange a weekend of cross-country skiing, and imagine yourself on the balmy beaches of Montana.

Or, you may return to your job, whichever you desire. Three hundred and fifty million years ago, a shallow, warm sea covered the area that is today Montana, Idaho, Wyoming, and the Dakotas. The ocean level was indeed so high that the majority of the western hemisphere was submerged. Experts equate the water that blanketed Montana to that of the Gulf of Mexico: warm, shallow, and dense with microscopic marine creatures.

When these animals passed away, their remains fell to the bottom of the murky ocean. Over countless eons (millions and millions of years), their bones were compacted and transformed into Madison Limestone, a common pale gray rock in Montana, Idaho, Wyoming, and the Dakotas.

Limestone is an intriguing substance. On the one hand, it is porous and calcite (the primary component of both limestone and Tums) is relatively simple to dissolve, resulting in the development of the Lewis and Clark Caverns and other caverns in Southwest Montana. In contrast, Montana’s dry environment and alkaline soil make Madison Limestone the hardest rock in the state.

The majority of Montana’s mountains have limestone pinnacles, and the majority of the cliffs, ridges, and most prominent features (such as the canyon along the Clark Fork or the Beaverhead formation near Dillon) are composed of Madison Limestone. Due of limestone’s resilience in Montana’s environment, it has been used in many of the state’s landmark structures, such as the Montana State Capitol.

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Before 80 million years ago, the midcontinent was covered by a warm, shallow inner sea that extended from the Arctic Ocean to the Gulf of Mexico and was at least one thousand miles wide at the modern border between Canada and the United States. Newly developed mountains to the west were unstable.

As volcanoes evolved, numerous earthquakes occurred. Volcanic ash and fine muds were transported by wind and water currents to the ocean floor, where they accumulated as sediment. WESTERN INTERIOR SEAWAY During the Cretaceous period, the majority of Manitoba was covered by a warm, shallow sea known as the Western Interior Seaway.

There was little to no permanent ice at the poles, and global temperatures were greater. Sea levels were also higher. The sea overwhelmed all low-lying portions of the world’s continents. The Seaway in North America extended from the Gulf of Mexico to the Arctic, essentially splitting the continent into two enormous islands for millions of years.

The sea, also known as the “Mid-Continental Seaway,” must have sustained a rather constant climate for ages. The climate at the period was drastically different from that of the present. There was minimal daily or seasonal variation in temperature. Throughout the Upper Cretaceous, this region remained surprisingly stable as a tropical or subtropical zone.

ANIMAL LIFE During the Upper Cretaceous, animal life was abundant and diverse. This warm, salty water was teeming with reptiles, such as four varieties of mosasaurs, plesiosaurs, and large sea turtles. In addition, there were at least two species of birds, Hesperornis and Ichthyornis, as well as various kinds of fish, squids, and sharks.

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How do interior lands form?

An epeiric sea is a shallow body of water with minimal connection to the ocean. Only when a continental interior is flooded by marine transgression owing to sea level rise or epeirogenic movement is an inland sea an epeiric sea. An epicontinental sea and an epeiric sea are synonymous.