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
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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 -1 a, 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 • SO 2 reflects sunlight = cooling • CO 2 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 CO 2 & H 2 O • H 2 O condense to oceans • CO 2 dissolved in oceans: carbonate rocks, little for atm. • Additional O 2 from photosynthesis • Today: N 2, O 2 All Others Oxygen Nitrogen
34 Mass Extinctions: Atmosphere-Ocean Interaction (1) § CO 2 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 § CO 2 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
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41 What is wrong?
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