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THE EARLY MESOZOIC. Middle Life Intermediate Evolutionary Forms “The Age of Reptiles” Dinosaurs ruled the Earth Evolution of Birds, Mammals and Flowering Plants 182 million years. The Early Mesozoic. Triassic- Tri or Three Friedrich August von Alberti

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  1. THE EARLY MESOZOIC • Middle Life • Intermediate Evolutionary Forms • “The Age of Reptiles” • Dinosaurs ruled the Earth • Evolution of Birds, Mammals and Flowering Plants • 182 million years

  2. The Early Mesozoic • Triassic- Tri or Three • Friedrich August von Alberti • Unit between Zechstein and Lias Limestones of Germany • Red non-marine sandstones-Marine Muschelkalk-Red non-marine marls and clay • Jurassic • Highly fossiliferous, ammonites • Alexandre von Humboldt> Jura-kalk-stein, 1799 • Jura Mountains: France & Switzerland • 85 my


  4. Paleogeography • Continental fragmentation> Rifting • Break-up occurred in Late Triassic • Northern hemisphere rifted from southern and then east rifted from west producing many blocks • In the Jurassic, Gulf of Mexico continued to open

  5. East Coast of the US • Rifting >Atlantic Ocean • Fault-block basins along • the east coast from Nova • Scotia to S. Carolina • Triassic Redbeds and Basalts • The Newark Supergroup • Fluvial & Lacustrine Red • beds • Sills and Dikes • Vertebrate Footprints


  7. Three-toed Dinosaur Footprint- Newark Supergroup

  8. GULF of MEXICO- Evaporite sequences of the Jurassic deposited in the initial rift sequence The salt domes can be as high as 20km and have 2km diameters Salt rises due to low density These diapirs are good oil traps in Texas and Louisiana

  9. Tectonic History • Cordilleran Orogenic Belt • Western North America-South America • 300-1000km wide • Terrane accretion • Wrangelia Traveled 5000KM • Jurassic to today

  10. Middle Triassic Sonoman Orogeny Early Jurassic Nevadan Orogeny Suturing of Exotic terranes to western US

  11. Deformed Bedded Cherts of the Franciscan Fm., CA

  12. Orogenic events created igneous plutonic intrusions, batholiths, like the Sierra Nevada Batholith and the Idaho Batholith

  13. Sierra Nevada Batholith Yosemite

  14. NEOPROTEROZOIC TO CENOZOIC TRANSGRESSIONS AND REGRESSIONS OBSERVED ON THE CRATON Variable sea level represented sequences of sediments bounded by unconformities on all of the cratons - Regression, very low sea level during the Triassic Zuni Transgression in Jurassic through Cretaceous, very high sea level

  15. Early Jurassic of the Western US

  16. Chinle Fm. Petrified Forest

  17. Petrified National Forest

  18. Eolian Cross Bedding in the Early Jurassic Navajo Sandstone

  19. Economic Minerals: Carnotite, Uranium Ore

  20. Regular Echinoid Cidaris Irregular Echinoid Hemiaster Rapid Radiation of Mesozoic Sea Urchins

  21. Ceratitic Ammonoid from the Triassic Radiation of the Ammonoids Best Index Fossils for the Jurassic

  22. Diversification of Reptiles Marine Reptiles Ichthyosaurs Flying Reptiles Pterosaurs The Dinosaurs Pelvic Bone Arrangement Saurischian Ornithischian Saurischian Ornithischian

  23. The Dinosaurs: Middle Triassic Differences Based on Pelvic Bone Arrangement: Late Triassic Evolution • Saurischian • Lizard Hipped, earliest group • Similar to thecodonts • Theropods (carnivorous dinosaurs); Prosauropods (herbivores); Sauropods (large herbivores) • Ornithischian • Bird Hipped, differentiated • Herbivorous dinosaurs evolved from Prosauropods

  24. Carnivorous vs. Herbivorous • Carnivores • large head compared to body • Tyrannosaurus velocity 60km/hr • Herbivores • small head compared to body • Apatosaurus velocity 10-12km/hr

  25. Plateosaurus: Late Triassic Sauropod ancestor Herrerasaurus: one of the oldest Dinosaurs from the Triassic Coelophysis: Theropod, carnivorous Dinosaur The Sauropods: Largest of the Dinosaurs

  26. The Dinosaurs • Approximately 700 species in 300 genera • Warm Blooded • Rapid metabolism; prey-predator ratio; many blood vessels pores in the bones • Reproduction and Habits • Nesting behavior and social behavior (herds) • Characteristics • Eoraptor earliest thecodont; sauropods long necks and large body quadrupeds; Ornithopods are bi-pedal herbivores (Camptosaurus); Stegosaurs and Ceratopians are quadruped herbivores • Extinction>Late Jurassic-Early Cretaceous/End K

  27. Mammals • Mammal-like reptiles therapsids (cynodonts) • Early Triassic small cynodont gave raise to medium size carnivores and herbivores that are ancestral to mammals • Late Triassic a small cynodont gave rise to the earliest mammal the morganucodontids • Most Triassic and Jurassic mammals were insectivores and very small

  28. Archaeopteryx: Jurassic Bird or Feathered Dinosaur from the Solnhofen Fm. Of Germany Birds arose from coelosaurs in the Jurassic. Early birds differed from dinosaurs in feathers and a wishbone Teeth were lost in all birds before the end of the Cretaceous and the tail was shortened The pelvic structure was first similar to other theropods (saurischians) but later through parallel evolution shifted to an ornithischian form

  29. Climates • Warming trend which reached a maximum in the Late Jurassic and Cretaceous • Variable and cooler temperatures since Late Cretaceous • Abundant redbeds, evaporites and carbonates • Warmer mid latitude and high latitude rainfall as evidenced by coal deposits for a mild polar condition • Oxygen levels were low during Triassic (15%) and rose to 25% then lowering to 21% by the Late Jurassic

  30. The Cretaceous Terrain Cretace, France Creta: Chalk (Latin) J.J. d’Omalius d’Halloy (1822)/ Conybeare & Phillips (1822) 144 my to 66.4 my

  31. Chalk: White Cliff along the Dorset Coast of Southern England Close-up of chalk with flint (chert) nodules Higher CO2 from rifting higher productivity of phytoplankton (coccolithosphorids), chalk deposits and higher O2

  32. Cretaceous • 70 my • Sea level higher>> epeiric seas • Divergence of planktic organisms • Large coal and oil deposits • Atlantic continued to open • Tethys closed • India migrated northward • 3rd largest mass extinction K/T

  33. Paleogeography • Tectonic events • Rifting between Africa-S. America; • India-Antarctica/Australia; • Britain-New Foundland; • Madagascar-Africa • Collisions Sevier and Laramide orogeny in western US

  34. Cordilleran Orogenic System • Terrane accretion • Subduction • Intense deformation • Fold-thrust belts • Plutonism & Volcanism • Sevier Orogeny • 130-80 my • Laramide Orogeny • 80-50 my

  35. Cross-section indicating major tectonic features present in the Cretaceous across the western US Fold/Thrust Belt Melange

  36. Sevier type deformation consisting of thrust faults

  37. Highest stand of sea-level 280m above current Atlantic coastal plain subsiding Florida was a shallow submarine carbonate bank Black shales: carbonaceous matter from unoxidized phytoplankton due to lack of polar cold water circulation

  38. Diagrams indicating how rapid sea-floor spreading can cause displacement of water onto continents

  39. Fall Line Area of outcrop of Cretaceous limestone and marl in the Atlantic and Gulf Coast Coastal Plain

  40. Cretaceous Climates • Warm tropical climates • Shallow seas, carbonates • Coal, bauxite evidence of humid conditions • Tropical and subtropical climates extended from 45oN to 70oS • Polar regions mild • Widespread reefs (Rudists and Corals) • Oxygen levels 30% to 35%

  41. Warm Climates • Decrease reflection of sunlight by high stands of sea levels • water absorbs more heat • Paleogeographic changes- • changes in currents due to plate tectonics, circumequatorial current • Increase CO2 in the atmosphere released by mantle plumes, greenhouse effect

  42. Economic Deposits • Oil, Gas and Coal • Oil • Phytoplankton-biologic material-source beds • Heat-converts to hydrocarbons • Permeable beds- reservoir • Geologic traps-impermeable beds

  43. Cretaceous Life • Marine Communities • Pelagic diversification of planktic coccoliths, forams, diatoms and dinoflagellates; • Nektics ray-fin fishes (Teleost), ammonoids, plesiosaurs, ichthyosaurs, mosasaurs • Benthic forams, major expansion of filter and deposit feeders • Terrestrial Communities • Appearance of angiosperms • Coevolution of pollinating insects

  44. Extinctions • K/T Boundary • Dinosaurs, pterosaurs, many marsupial mammals became extinct • Extinction for terrestrial organisms only 15% • Marine extinctions at the generic level 70% • All ammonites, rudists, marine reptiles

  45. Causes of Extinction at the K/T Boundary • Sea Level changes • Temperature changes • Increased seasonality • Changes in plant distribution and extinction • Increased competition with mammals • Bolide collision

  46. Impact Theory • Iridium Anomaly • clay around K/T enriched in Ir • Spherules • glass beads, felsic, melting of crustal rocks • Soot • carbonaceous particles, wildfires • Shocked Quartz • lamelle > high pressure shock wave • Stishovite • high pressure form of quartz

  47. Occurences of Iridium-rich sediments at the K/T Shocked Quartz Iridium-rich clay layer Gubbio, Italy Tertiary Cretaceous

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