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Cantwell Formation
Geologic formation in Alaska, United States From Wikipedia, the free encyclopedia
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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 America during the Late Cretaceous for many families of dinosaur. Fossil plants of water lilies found in the same area suggest the presence of wetlands, ponds or other large standing bodies of water.[1]
Footprints discovered in the formation include those of theropods, hadrosaurs, ceratopsians, pterosaurs and birds, notably the Magnoavipes denaliensis.[2][1]
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The Cantwell Formation represents a Late Cretaceous fluvial succession in Denali National Park containing dinosaur trackways, invertebrate traces, and plant fossils. Sedimentary facies represent a lateral succession from alluvial fan and braided river deposits, to coastal fluvial and lacustrine environments with marshy overbanks, proximal estuary consisting of laterally avulsed distributary channels, intertidal estuarine deposits, and finally tidally influenced marginal marine environments.[3]
A leaf analysis of the Sable Mountain flora was used to estimate a mean annual temperature of 7.42 °C (45.36 °F), a warm month mean temperature of 17.1 °C (62.8 °F), and a cold month mean temperature of −2.3 °C (27.9 °F). Growing season precipitation was estimated at 229.4 millimetres (9.03 in) over a period of 4.8 months. These results demonstrate a cool temperate, seasonal paleoclimate with short dry summers and cold wet winters.[4] Dating of ash layers in the formation indicate this floral assemblage straddled the Campanian-Maastrichtian boundary, a period of rapid global cooling.[5]

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Flora
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Notes Uncertain or tentative taxa are in small text; |
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