Lecture 5

Question 1

Taphonomy

Answer 1

Study of what happens to the remains of an animal from time of its death to the time of discovery

Question 2

Burial

Answer 2

Carcass covered with sediment

Interrupts decomposition

Question 3

Petrification

Answer 3

Skeletal remains absorb surrounding minerals that eventually replace the organism’s inorganic tissues

Question 4

Stratigraphy

Answer 4

• Strata=Layers in rock, indicate relative age
• Uniformitarianism, developed by James Hutton
• Looks like layers in a cake, but earthquakes deform these horizontal layers

Question 5

Four principles of Geological Stratigraphy

Answer 5

1. Principle of original horizontality
2. Principle of superposition
3. Principle of cross-cutting relationships
4. Principle of faunal succession

Question 6

Principle of original horizontality

Answer 6

Sedimentary rocks are always originally deposited in more or less horizontal layers

Question 7

Principle of superposition

Answer 7

Older layers are laid down first and covered by younger layers

Question 8

Principle of cross-cutting relationships

Answer 8

Geological feature when a rock cuts another, it is younger

Question 9

Principle of faunal succession

Answer 9

• Index fossils typify the animal in layer

- Successive layer contain certain types of faunal communities with predictable patterns

Question 10

Geologic Time Scale (GTS)

Answer 10

• Earth is 4.5 billion years old
• Human/Primate evolution last 65 million (cenozoic)
• Divided into eons, eras ,periods, epochs

Question 11

Relative Dating Techniques

Answer 11

Dating techniques that establish the age of a fossil only in comparison to other materials found above and below it

Question 12

Lithostratigraphy

Answer 12

The study of geologic deposits and their formation, stratigraphic relationships, and relative time relationships based on their lithologic (rock) properties

Question 13

Tephrostratigraphy

Answer 13

• Form of lithostratigraphy in which the chemical fingerprint of a volcanic ash is used to correlate across regions
• Identification of volcanic ask by its chemical fingerprint
• Variant of lithostratigraphy

Question 14

Biostratigraphy

Answer 14

• Relative dating technique using comparison of fossils from different stratigraphic sequences to estimate which layers are older and which are younger
• Principle of faunal succession
• Rodents often good indicators

Question 15

Chemical Techniques Within Sites

Answer 15

Analysis of fluorine, uranium, and nitrogen content of the fossils themselves

Question 16

The Piltdown Hoax

Answer 16

• was the deliberate fabrication of a fossil involving an ancient human cranium and a modern ape jaw
• Exposed by fluorine analysis

Question 17

Calibrated Relative Dating Technique

Answer 17

• Techniques that can correlated to an absolute chronology

- Regular processes calibrates to a chronological are known

Question 18

Geomagnetic Polarity

Answer 18

• Reverse polarity
• -North and South magnetic poles
• -Today, rocks orient toward magnetic north

Question 19

Geomagnetic Polarity Time Scale (GPTS)

Answer 19

• Time scale composed of the sequence of paleomagnetic orientation of sediments through time
• Provides expectation of rock polarity at any given chronological age

Question 20

Paleomagnetism

Answer 20

• ancient sediments

- show how Earth’s magnetic pole has changed through geologic time

Question 21

Chronometric Dating Techniques

Answer 21

• Techniques that estimate the age of an object in absolute terms through the use of natural clock, such as radioactive decay or tree ring growth
• Estimate antiquity of an object in years before present
• Relies on natural clock, clocklike decay
• Elements reduced to carbon, hydrogen, oxygen and molecules of water and carbon monoxide

Question 22

Radiometric Dating

Answer 22

• Chronometric techniques that use radioactive decay of isotopes to estimate age
• Isotopes are variants of a particular chemical element that
• -has same number of protons
• -different number of neutrons
• Isotopes decay over time
• -HALF-LIFE of isotope is the amount of time it takes for one-half of the original amount to decay
• -PARENT is the original radioactive isotope
• -DAUGHTER (product) is the sample

Question 23

Potassium- Argon dating

Answer 23

• Radiometric technique using the decay of 40K to 40Ar in potassium-bearing rocks; estimates the age of sediments in which fossils are found.
• Useful in dating the timing of eruption of volcanic sediments
• Limited; requires both solid and gases

Question 24

Argon-argon Dating

Answer 24

• Radiometric technique modified from K-Ar that measures 40K by proxy using 39Ar. Allows measurement of smaller samples with less error.
• Smaller sample and greater control over measurements
• Increased confidence in age

Question 25

Cosmogenic Radionuclide Techniques

Answer 25

- Radiometric dating technique that uses ratios of rare isotopes such as 26A, 10Be, and 3He to estimate the time that sediments and the fossils in them have been buried. - Relatively new - 26Al/10Be - Quantz gain - Used in non-volcanic environments - Relationship btw sediments and fossils must be known

Question 26

Uranium Series Techniques

Answer 26

- Radiometric techniques using the decay of uranium to estimate an age for calcium carbonates including flowstones, shells, and teeth - Decay chain of 238U, 235U and 232Th - No daughter products are present when flowstone formed - Method to date directly with uranium techniques more complicated - In- and out- migration unpredictable

Question 27

Radiocarbon dating

Answer 27

- Radiometric technique that uses the decay of 14-C in organic remains such as wood and bone to estimate the time since the death of the organism - Primary techniques for estimating antiquity from Pleistocene through the present - All living organisms contain carbon - Limited to objects younger than 40,000 years

Question 28

Electron Trap Techniques

Answer 28

measures the effect of exposure to radioactivity

Question 29

Thermoluminescence (TL)

Answer 29

- Measures number of trapped electrons by measuring amount of light given off when released - Useful in dating pottery that was fired - Typically used in range of past 100,000 years

Question 30

Optically Stimulated Luminescence (OSL)

Answer 30

Dates materials whose traps were emptied by bleaching from sunlight

Question 31

Pangaea

Answer 31

- late triassic period | - 150 million years (late jurassic)

Question 32

LAURASIA

Answer 32

-Present-day North America, Europe, Asia

Question 33

GONDWANALAND

Answer 33

Africa, South America, Antarctica, and Australia/India

Question 34

Climate in Cenozoic

Answer 34

- 16 O and 18 O (indicating warmer/colder periods) - -Stable isotopes of oxygen that exists in water molecules and other compounds - -Ration measured by marine geologists because higher ratio of 10O/ 16O indicates colder climates and lower seas levels - More 18O indicates colder periods and more 16O indicates warmer periods

Question 35

Paleosols and Loess

Answer 35

- Ancient soils can correlate strata between sites - Carbonates used to understand local climates - Unclear base ratios - Loses is windblown sediment that provides some paleoclimatic and environmental information

Question 36

Vegetation

Answer 36

- Plant macrofossils - compare ancient environments to today - fossil pollens

Question 37

Animal Communities

Answer 37

- Preferred types of habitats of past animals can be inferred - Focus on community of animals at a particular site, not single species - Dietary and locomotor adaptation

Question 38

Dolinas

Answer 38

sink holes