Fossils and the Discovery of Earth History

1. Lecture 004 Fossils and the Discovery of Earth History

2. FOSSIL Evidence of the existence of past life

3. Problems with using fossils: • only organisms with hard parts will be fossilized and leave a record • if you find a fossil in a certain place, it doesn’t mean it lived there; example-continent moved after extinction • record is uneven in time and area • many fossils that get preserved are a dead end • most of record is lost or unexplored; missing link- look at homonids

4. Benefits of using fossils: • provides evidence that it once existed • provides minimum ages • documents extinction’s • use them to put together scenarios in paleoclimatology or extinction/immigration scenarios-----complete record with Hyracotherium

5. Horse Evolution

6. Horse Evolution Timeline Hyracotherium Pliohippus 55 mya 10 mya Miohippus EOCENE ERA OLIGOCENE ERA 30 mya OLIGOCENE ERA Equus Mesohippus 4 mya MODERN ERA Merychippus 40 mya OLIGOCENE ERA 20 mya OLIGOCENE ERA

7. Hyracotherium 55 mya Miohippus 35 mya Merychippus 17 mya Equus modern Note: diagram is scaled so organisms appear to be the same size

8. TYPES OF FOSSILS Body Fossils Remains of the organism itself Trace Fossils Evidence of the movement or activity of the organism

9. Body Fossils stingray fish

10. TRACE FOSSILS Tracks and Trails Burrows and Borings Coprolites

11. Trace Fossils Tracks Trails

12. Trace Fossils Burrows & Borings This section of fossil conifer wood is Cretaceous of the Antarctic Peninsula.The round holes, filled with brown mudstone or white crystals, were formed by wood-boring bivalves that bored into the log while it was floating on the Cretaceous seas as driftwood.

13. Trace Fossils Coprolite

14. Modes of Body Part Preservation • 1. Unaltered fossils • Soft parts (rare) & Hard parts • A. peat bogs • B. amber • C. tar pits • D. mummification or desiccation • E. refrigeration Jellyfish fossil- Precambrian Edicarian Fauna

15. Modes of Body Part Preservation • 2. Altered fossils • petrifaction • permineralization • replacement • recrystalization • carbonization

16. Modes of Body Part Preservation • 3. Imprints • molds • impressions

17. 1. Unaltered Fossil A. Peat bog A variety of fossils preserved by rapid burial in this anaerobic environment.

18. 1. Unaltered Fossil B. Amber With Insects Amber is the pitch from conifer trees

19. Mosquito in Amber

20. 1. Unaltered Fossil C. Tar Pits La Brea Tar Pit Ground Sloth

21. 1. Unaltered Fossil D. Mummification Leonardo Duck-billed dinosaur 77 myo. Montana

22. 1. Unaltered Fossil E. Refrigeration Wooly Mammoth frozen in Siberia (found 1987)- 20,000 years old

23. 2. Altered Fossil Petrifaction Permineralized- original pore space is filled in with minerals Shark’s Tooth

24. 2. Altered Fossil Petrified wood

25. 2. Altered Fossil Carbonization coal

26. 3. Imprints Glossopteris impression Gastropod mold

27. Other Kinds of Evidence For Past Life Gastroliths Fossil Fuels

28. Characteristics of Fossils Known to the Ancients • Fossils exhibit great diversity in forms, some resembling living forms, some appearing very different from modern forms. • Physical consistency is usually that of stone rather than of the materials exhibited by comparable living species. • Many fossils are found high in the mountains resembled forms that normally occur in the ocean. • Fossils are often found encased in hard stone.

29. Evidence for Early Human Interest in Fossils • 80,000 year old Neanderthal site with fossil snail and coral skeletons. • 35,000 year old Cro-Magnon burial site with fossil-shell necklaces. • Early Egyptian site (perhaps 3200 B.C.E.) with fossil mounted in metal. • It is possible, but not certain, that these prehistoric peoples regarded fossils as magical.

30. Mythical Ideas About Fossils Fossils grew in the rocks No distinction between fossils and crystals and ores Magical and curative powers Artifacts of the Devil

31. Diluvialism Tertuillian 155 - 222 C.E. The view that great floods were a major contributor to earth evolution Example of catastrophism

32. Leonardo da Vinci 1452 - 1519 • Observed fossils on mountains • Rejected flood theory • Argued that the earth is old • Grasp concept of superposition

33. Robert Hooke (1635-1703) Petrified Wood Studied fossils and compared them to living organisms

34. Nicholaus Steno 1638 - 1686 Compared sharks teeth to “tongue stones” Argued that fossils could be altered in chemical composition without changing their form Steno’s Law of Superposition

35. Superposition Superposition

36. Stratigraphic setting of the Cambrian Burgess Shale 505 MYA 540 MYA

37. Georges-Louis Leclerc de Buffon 1707 - 1788 Origin of the Earth- collision of a comet with the sun Age of Earth ~75K

38. Histoire Naturelle

39. Extinction

40. Baron Georges Cuvier 1769 - 1832 Catastrophist Species don’t change over time Theory of extinction

41. Catastrophism • Fossil record provided evidence for catastrophes • Earth is young • E.g. Noah’s flood • Recent: meteor impact & volcanism

42. William Smith 1769 - 1839 Development of the Geologic Time Scale Principle of faunal succession

43. Correlating Rock Layers

44. Geologic Time Scale

45. James Hutton 1726 - 1797 • The Rock Cycle • Deep Time • Uniformitarianism

46. The Rock Cycle

47. Deep Time "we find no vestige of a beginning and no prospect of an end"

48. Uniformitarianism • The present-day earth has been shaped slowly by everyday forces of erosion and deposition • Earth is old • E.g., erosion & uplifting = mountains

49. Charles Lyell 1797 - 1875