Transcript Slide 1
1 Geological History & Extinctions 2 FOSSIL The trace of an organism buried naturally and subsequently preserved permanently 3 Fossilisation • Original soft parts (rare) • Original hard parts (unaltered) • Original hard parts (altered) • carbonization • Petrification • Replacement or mineralisation 4 Taphonomy -The study of the postmortem history of an organism 5 6 Illustration of Principle of Faunal Succession 7 Climate Proxies 8 Speleothem growth as a climate proxy: Glacial Interglacial 9 Spelothem growth as a climate proxy: Glacial Interglacial 10 The Ipswichian - 125000 years ago in Leeds 11 86000 years ago in Leeds 12 Body Fossils Alum Bluff Mystery Fossils Leaves from Miocene of Alum Bluff, Florida 13 Body Fossils? 14 Microfossils 15 Trace Fossils 16 “Living Fossils” Ginkgo biloba 17 Metasequuoia gyptostroboides Geologic time (millions of years) 18 Geologic Time & Biology Geologic time (millions of years) 19 Geologic Time & Biology 20 Geologic time (millions of years) Geologic Time & Biology Fig. 4-1a, p.74 21 Geologic Time • MAJOR DIVISIONS • Cenozoic: 66 - 2.5 m.y.a • Mesozoic: 245 - 66 m.y.a. • Paleozoic: 544 - 245 m.y.a. • Precambrian: pre-544 m.y.a. (Proterozoic) Geologic Time • Eon/Era/Period - relative ages (fossils, stratigraphy ) • Dates: absolute ages (radiometric dating) 22 23 Precambrian (4.6 Ga – 570 Ma) • • • • Comprises 88% of Earth History First continents, plate tectonics Rock record poorly preserved Life evolves, but rarely preserved as fossils 24 Paleozoic Era (570 Ma - 245 Ma) Continents are widely separated Continents collide - Pangea Reptiles & amphibians 25 Mesozoic Era (245 Ma – 66 Ma) • Breakup of Pangea • Opening of Atlantic Ocean • Dinosaurs, mammals, flowering plants Cenozoic Era (66 Ma - present) Mammals & grasses India-Asia collide Australia moves N. Rocky Mts. form 26 Mass Extinctions Def.: catastrophic events • that abruptly killed most • life on Earth & allowed • new life forms to emerge • • Scientists debated origin • Evidence for at least 5 • mass extinctions • Causes? 27 A Bad Day…. 65 Million Years Ago • The Asteroid: ~10 km • dinosaur extinction? • The Impact • Chicxulub Crater (Yucatan) • 300 km underwater crater • The Result • Cretaceous Extinction 28 Mass Extinctions: Extraterrestrial Impacts 29 • Meteoric impact - explosion • Thick cloud of dust, blocks sunlight • Ocean? Fig. 4-2, p.75 Mass Extinctions: Volcanic Eruptions 30 • Eruptions of gas & volcanic ash - contaminate atmosphere • SO2 reflects sunlight = cooling • CO2 blocks radiated energy = warming Fig. 4-2, p.75 31 Example Eruptions: • Historic “regular” big eruptions: up to 50,000 fatalities • “ Siberian Traps”: 250 Ma, massive eruption: almost area of USA Fig. 4-2, p.75 32 Mass Extinctions: Atmosphere-Ocean-Continent Interactions • Ocean-Atmosphere: Ocean currents mix heat & gases from oceans to atm. • Ocean-Continent: Ocean currents partly controlled by positions of continents Fig. 4-2, p.75 33 Evolution of Earth Atmosphere • Initially: thick atmosphere of CO2 & H2O • H2O condense to oceans • CO2 dissolved in oceans: carbonate rocks, little for atm. • Additional O2 from photosynthesis • Today: N2, O2 All Others Oxygen Nitrogen 34 Mass Extinctions: Atmosphere-Ocean Interaction (1) CO2 transferred from atmosphere to ocean Atmosphere cools Fig. 4-2, p.75 35 Mass Extinctions: Atmosphere-Ocean Interaction (2) Cooling water sinks: stirs up deep ocean CO2 sent back to surface, kills organisms 36 Mass Extinctions: Atmosphere-Ocean-Continent Interactions • Ocean-Atmosphere: Ocean currents mix heat & gases from oceans to atm. • Ocean-Continent: Ocean currents partly controlled by positions of continents Fig. 4-2, p.75 Mass Extinctions: Ocean-Continent Interaction Supercontinent “Pangea” Single land mass prevented mixing of ocean 37 38 39 40 41 What is wrong? 42