HOWEVER WE MUST BE ABLE TO PUT THEM IN THE RIGHT SEQUENCE OR THE STORY THEY TELL DOESN T MAKE SENSE, JUST LIKE A BOOK WITH ITS PAGES OUT OF ORDER

Transcription

1 HOWEVER WE MUST BE ABLE TO PUT THEM IN THE RIGHT SEQUENCE OR THE STORY THEY TELL DOESN T MAKE SENSE, JUST LIKE A BOOK WITH ITS PAGES OUT OF ORDER DOESN T MAKE SENSE: ACCURATE DATING METHODS ARE ESSENTIAL TO THIS PROCESS

2 SOME INITIAL DEFINITIONS: FOSSIL: THE REMAINS OF PLANT/ANIMAL SKELETAL STRUCTURE CAN BE AN IMPRESSION OR THE REAL THING

3 IF STRUCTURE EXISTS, IT S MADE OF MINERAL/STONE, NOT BONE!

4 ARTIFACT: OBJECTS OR MATERIALS MADE OR MODIFIED FOR USE BY HOMINIDS

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6 CONTEXT THE RELATIONSHIP BETWEEN AND AMONG ARTIFACTS AND OTHER MATERIALS THIS CONCEPT IS CRITICAL TO THE EXAMINATION AND UNDERSTANDING OF FOSSILS AND ARTIFACTS W/O CONTEXT, ARCHAEOLOGICAL DISCOVERIES DON T HAVE MUCH MEANING

7 DATING METHODS RELATIVE DATING PROCEDURES: STRATIGRAPHY: THE LAYERING OF DIRT, ROCK FORMATIONS, AND FOSSILS THE LOWER THE DEPTH THE OLDER THE AGE

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9 TAPHONOMY STUDY OF PROCESSES OF SITE DISTURBANCE AND DESTRUCTION

10 CHEMICAL DATING: MEASURES FLUORINE, URANIUM, & NITROGEN IN TEETH & BONES SAMPLES MUST BE FOUND IN GROUNDWATER AND IN CLOSE PROXIMITY SITES

11 HOW IT OPERATES: AS TIME GOES BY: FLOURIDE AND URANIUM= INCREASES IN SAMPLE NITROGEN= DECREASES URANIUM DOESN T DESTROY SAMPLE,SO PREFERRED METHOD

12 ALL ELEMENTS FOUND IN NATURE

13 PALEOMAGNITISM: INVOLVES PERIODIC PAST REVERSALS OF EARTH S MAGNETIC POLES

14 ROCK FORMATIONS (ESP. LAVA) RETAIN EARTH S MAGNETIC FIELD WHEN LAID DOWN

15 LAVA BONES INDIRECTLY MEASURED BY POLARITY DATES

16 BIOSTRATIGRAPHY LOOKS AT FAUNA/FLORA FOSSILS OF SHORT-LIVED SPECIES IN PARTICULAR REGION

17 TONS OF CHARTS & STUDIES

18 PIGS ESP. HELPFUL IN AFRICA

19 CHRONOMETRIC (ie. ABSOLUTE) DATING METHODS DENDROCHRONOLOGY: LOOKS AT TREE RINGS NEED SENSITIVE TREES OVER COMPLACENT TREES THEY RESPOND TO PRECIPITATION, HEAT, ETC

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21 BEST WHERE WOOD IS PRESERVED (IE. ARID AMERICAN S.W.) CLIMATE VARIATIONS ARE CRITICAL CAN GO BACK 10,000 YA BUT SHAKY (7500 YA BETTER) BRISTLE CONE PINE IS BEST TREE B/C THERE ARE THE WORLD S OLDEST TREES

22 THE METHUSALA TREE : 4,800 YEARS OLD, CALIFORNIA

23 VARVES: LAKE SEDIMENTS DEPOSITED BY ANNUAL GLACIER MELTS FROM LAST ICE AGE SUMMER CLIMATE VARIATIONS TRACKED GOOD UP TO 20,000 YA (BEST 10,000-15,000); USED IN DATING SITES IN N. AMERICA; N. EUROPE

24 EXAMPLES OF VARVES

25 THERMOLUMINESCENCE: MEASURES LIGHT EMITED FROM SAMPLES PREVIOUSLY HEATED IN PREHISTORIC TIMES EXAMINES RADIOACTIVE PROPERTIES EXCELLENT UP TO ABOUT 10,000 YA (BUT BEEN USED TO 70,000 YA) EX S: CAMPFIRE STONES, BURNT POTSHARDS, FLINT

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27 ELECTRON SPIN RESONANCE DATING LIKE THERMO, MEASURES TRAPPED ELECTRONS SPINS MATERIAL W/IN MAGNETIC FIELDS AND MEASURES MICROWAVES/RADIATION

28 NO HEAT INVOLVED: GOOD FOR BONE AND SHELL

29 CARBON-14: MEASURES AMOUNT OF RADIOACTIVE CARBON ISOTOPE C- 14 DEAD FAUNA/FLORA DECLINES AT CONSTANT RATE AFTER DEATH GOOD UP TO 40,000-50,000 YA WHICH IS WHEN H. sapiens ENTER EUROPE

30 C-14 PHIALS AND MACHINE

31 SHROUD OF TURIN: C-14 TESTING 1988 U. OF OXFORD, U. OF ARIZONA, SWISS FEDERAL INSTITUTE OF TECHNOLOGY

32 RESULTS: DATED BETWEEN AD (MIDDLE AGES) 3 PEER-REVIEWED ARTICLES DISPUTE RESULTS BASED ON: SITE OF SHROUD SAMPLES POSSIBILITY REPAIRS OR CONTAMINATION AFFECT DATES

33 POTASSIUM-ARGON (K-Ar): INVOLVES STEADY DECAY OF K-40 INTO Ar-39 POT-40 S ½ LIFE IS 1250 MILLION YEARS DECAYS INTO ARGON BLAST SAMPLE W/ NEUTRON BEAM, MEASURE TRAPPED ARGON

34 DATES P-RICH ROCK SURROUNDING FOSSILS, NOT FOSSILS THEMSELVES EXTREMELY VALUABLE IN E. AFRICA MIOCENE (5-22 MILLION YA BUT CAN GO BACK 3+BILLION YA)

35 V. SCIENTIFIC: THOUSANDS OF DOLLARS A SAMPLE, WEEKS FOR RESULTS

36 FISSION TRACKING: COUNTS TRACKS ACROSS SAMPLE BY DISINTEGRATING URANIUM ATOMS (U-238) ACCURATE FROM 20 YEARS TO 5 BILLION YA

37 NEED ELECTRON MICROSCOPE AND COMPUTER TO COUNT TRACKS

38 CROSS-REFERENCING: COMBINING ABOVE METHODS HELPS ELIMINATE ERRORS K-AR DATING W/ FISSION TRACKING IS VERY ACCURATE USUALLY COSTS DETERMINE DATING METHOD