Cantwell Formation

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.

Footprints discovered in the formation include those of theropods, hadrosaurs, ceratopsians, pterosaurs and birds, notably the Magnoavipes denaliensis. Description 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.

A leaf analysis of the Sable Mountain flora was used to estimate a mean annual temperature of , a warm month mean temperature of , and a cold month mean temperature of . Growing season precipitation was estimated at over a period of 4.8 months. These results demonstrate a cool temperate, seasonal paleoclimate with short, dry summers and cold, wet winters. Dating of ash layers in the formation indicate this floral assemblage straddled the Campanian-Maastrichtian boundary, a period of rapid global cooling.https://www.researchgate.net/publication/278676602_New_zircon_U-Pb_ages_for_the_lower_Cantwell_Formation_implications_for_the_Late_Cretaceous_paleoecology_and_paleoenvironment_of_the_lower_Cantwell_Formation_near_Sable_Mountain_Denali_National_Park_an

Flora

Taxa Species Locality Material Notes ImagesAlnitesA. sp. Similar to extant Alnus.AspleniumA. sp. Cf. Castaliitescf. C. sp. Leaf morphotaxon.CephalotaxopsisC. sp. Belongs to Taxaceae.CorylitesC. beringianus Similar to extant Corylus.Cladophlebis C. sp. Cf. Craspedodromophyllumcf. C. sp. Belongs to Betulaceae.EquisetumE. arcticum GlyptostrobusG. sp. Fagales indet. Leaf morphotypes.Belongs to the “Higher Hamamelids”.Cf. Kenellacf. K. sp. SeedsLarix L. sp. Needle bundles.Originally described as Cf. Pseudolarix.Metasequoia M. occidentalisMenispermitesM. septentrionalisBelongs to Menispermaceae.M. sp. Another Menispermoid.Cf. Nupharcf. N. sp. Similar to extant Nuphar.Parataxodium?Indeterminate In need of revision.Cf. Phragmitescf. P. sp. PiceaP. sp. Needles, ovuliferous cone.Pinus P. sp. Needle bundles.Pityophyllum?indeterminateIndeterminate Pinaceous needles.PlatanitesP. sp. Belongs to Platanaceae.PseudoprotophyllumP. sp. Another Platanoid.Cf. Sparganiumcf. S. sp. TrochodendroidesT. richardsonii Belongs to Cercidiphyllaceae.T. sp. A Trochodendroid.Tumion T. gracilisCf. Viburniphyllcf. V. sp. Similar to extant Viburnum.Cf. Zizyphoides cf. Z. sp. Another Trochodendroid.

Cantwell Formation

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