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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.

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Presentation on theme: "THE EARLY MESOZOIC Middle Life Intermediate Evolutionary Forms “The Age of Reptiles” Dinosaurs ruled the Earth Evolution of Birds, Mammals and Flowering."— Presentation transcript:

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



7 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


9 Three-toed Dinosaur Footprint- Newark Supergroup

10 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

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

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

13 Deformed Bedded Cherts of the Franciscan Fm., CA

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

15 Sierra Nevada Batholith Yosemite

16 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

17 Early Jurassic of the Western US


19 Chinle Fm. Petrified Forest

20 Petrified National Forest

21 Eolian Cross Bedding in the Early Jurassic Navajo Sandstone

22 Economic Minerals: Carnotite, Uranium Ore

23 Regular Echinoid CidarisIrregular Echinoid Hemiaster Rapid Radiation of Mesozoic Sea Urchins

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

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

26 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

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

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

29 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

30 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

31 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

32 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

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

34 Chalk: White Cliff along the Dorset Coast of Southern England Close-up of chalk with flint (chert) nodules Higher CO 2 from rifting higher productivity of phytoplankton (coccolithosphorids), chalk deposits and higher O 2

35 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

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

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

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

39 Sevier type deformation consisting of thrust faults

40 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

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

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

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

44 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 CO 2 in the atmosphere released by mantle plumes, greenhouse effect

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

46 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

47 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

48 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

49 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

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

51 Meteor Crater, AZ 30m bolide Excavated 1.2km crater Phobos, a Martian moon about 20km diameter Location of Chicxulub structure

52 Volcanic Model Iridium as aerosol from volcanism Large eruption of flood basalts –Deccan Plateau –Periodicity of 30 my of basalts coincide with extinction peaks Sulfates >> acid rain > pH Cooling due to erupted ash

53 Erupted at 66 my 3 periods each lasting 50,000-100,000 yrs Millions of cubic kilometers of magma

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