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Alaska remained covered in seawater during the Triassic and Jurassic. Local wildlife included ammonites, belemnites, bony fish and ichthyosaurs. Alaska was a more terrestrial environment during the Cretaceous, with a rich flora and dinosaur fauna. During the early Cenozoic, Alaska had a subtropical environment.
During the Middle Triassic three large terranes—Wrangellia, Alexander and Stikine—remained offshore as separate island arcs not yet joined to the continent. The Wrangellia and Alexander terranes merged offshore by the Middle Jurassic and experienced folding and faulting during a collision with Alaska in the Cretaceous. The addition of the ...
The Cretaceous (IPA: / k r ɪ ˈ t eɪ ʃ ə s / krih-TAY-shəss) [2] is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest.
Sea levels reached their highest level in all of geologic history during the Cretaceous, although they declined before the period ended. [77] Scleractinian corals were more diverse during the Cretaceous than they are today. Back then coral reefs formed along the Gulf coast. [78] Rudist bivalves also constructed reefs in the Gulf coast region. [79]
The map of North America with the Western Interior Seaway during the Campanian. The Western Interior Seaway (also called the Cretaceous Seaway, the Niobraran Sea, the North American Inland Sea, or the Western Interior Sea) was a large inland sea that split the continent of North America into two landmasses for 34 million years.
The Schrader Bluff Formation is a geologic formation in Alaska. It preserves fossils dating back to the Cretaceous period, [4] Fossil remains include Inoceramus and Scaphites. [5] Originally named by George Gryc and others as the marine formation of the Colville Group (abandoned). [3]
The Cantwell Formation is a geologic formation in Alaska. It preserves fossils dating back to the Cretaceous period , it has also yielded numerous dinosaur tracks at Denali National Park . Contemporary therizinosaurid and hadrosaurid trackways in the formation indicate that the area was once a major point of immigration between Asia and North ...
This list of the Cenozoic life of Alaska contains the various prehistoric life-forms whose fossilized remains have been reported from within the US state of Alaska and are between 66 million and 10,000 years of age. Acanthocardia; Acirsa; Acmaea; Agonum †Ainus; A living Alces, or moose Alces; Alnus; Alopex †Alopex lagopus; Alvania; Amara ...