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Paleoenvironment of Utah: Fading the Mists of Time

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  1. Paleoenvironment of Utah:Fading the Mists of Time

  2. NA Southwest Late Permian • Pangea Supercontinent • Laurasia and Gondwanaland • Tethys Sea • Cutler and Kaibab Limestone

  3. Permo-Triassic Extinction • Most devasting mass extinction – 90-95% of marine species died out 75% of vertebrate families went extinct, synapsids heavily hit • Casualites: Trilobites, Tabulate and Rugose Corals, Pareiasaurs, Cordaites • Causes: Many! Severe climatic fluctuations, Siberian traps, Oceanic Overturn • Seen at Capital Reef NP

  4. NA Southwest Triassic • Pangea begins to break up • Adaptive radiation of flora and fauna • Archosauromorphs become dominant vertebrates • Utah = 5-10 degrees North of the Equator

  5. Early (240 Ma): Moenkopi Shinarump Conglomerate Late (215 Ma): Chinle Upper Triassic Triassic

  6. Globally warmer by 6˚C, with little latitudinal variation No polar ice caps Climatic Shift from warm and moist to hot and dry Large landmass = interior continental desert with high seasonality Utah: semiarid to subhumid climate Paleosols of Moenkopi record MAP 300-400mm and MAT 13-23˚C  desert shrub or dry woodlands Paleosols of Lower Chinle record MAP 700-900mm, but up to 1400mm and MAT 18˚C  open forest (Petrified Forest) Paleosols of Upper Chinle record MAP 400-600mm and MAT 29˚C  desert shrub or dry woodlands Triassic Paleoclimate

  7. Triassic Flora and Fauna • Flora: seed ferns, cycads, conifers • Fauna: Archosauria: Dinosaurs! • Climatic warming mirrored in floral and faunal turnovers Massospondylus Cycad Ceolophysis

  8. NA Southwest Jurassic • Pangea breaks up into North America, Eurasia, and Gondwana as the North Atlantic Sea opens • Tethys Sea closed • Spread of Dinosaurs

  9. Jurassic • Navajo Sandstone  Widespread Coastal Dunes • Great Navajo “sand sea” spreads across interior of Western North America. • Epicontinental seaway present = Some shallow marine excursions • Late Jurassic uplift to the West causes stream direction to reverse, expanding deposition of dinosaur fossil-bearing Morrison Fm Namibian Desert, SW Africa

  10. Globally warm and moist climate, prevailing up to the polar regions Southwestern North America: Arid Coastal Desert Thicknesses of annual depositional cycles within the Navajo Sandstone indicate strong near-equatorial, north-westerly winds Mountains to the West enhanced wind strength, and cast a rain shadow, allowing active dunes to extend very close to the palaeoequator. Jurassic Paleoclimate

  11. Jurassic Flora and Fauna • Conifers: most diverse, majority of tall trees • Cycads, tree ferns and gingkos • Age of Dinosaurs • Pterosaurs • First mammals Gingko Morganucodon

  12. NA Southwest Cretaceous • Break-up of Pangea into present day continents complete • Dinosaurs continue terrestrial dominance • Radiation of Angiosperms

  13. Cretaceous • Mancos Shale  Marine shale, overlain by shallow marine sandstones and fluvial deposits. • The Western Interior is the site of an encroaching epicontinental seaway from the north. • Mountain building orogenies to the West

  14. Cretaceous Paleoclimate • Globally warm and moist climate – Tropics 9-12˚C warmer than today, Deep Ocean 15-20˚ warmer than today • Increased Sea level = Epiconinental Seaways • Extensive tropical ocean stabilized global climate, gentle temperature laditudinal gradient • Weaker global winds

  15. Cretaceous Flora and Fauna • Angiosperms diversify, dominant Late Cretaceous – coevolution with insects • Age of Dinosaurs • Birds