Lecture 14

Question 1

Why was lithostratigraphy not useful for correlating strata in one region with those of another?

Answer 1

because the same environmental conditions produce the same or similar rocks throughout the world

Question 2

Where does later continuity work?

Answer 2

within a single deposition area

Question 3

What is William Smith known for?

Answer 3

Being the first person to produce a geological map of southern England (and later expanded out to other continents) in part observing the pattern of fossils throughout the strata. Through this he developed a new stratigraphic principle: biostratigraphy.

Question 4

What is biostratigraphy?

Answer 4

principle of fossil succession

Question 5

What is the principle of fossil succession?

Answer 5

There is a unique non-repeating pattern of fossils through stratigraphic time.
- all rocks containing fossils of the same species were deposited during the duration of that species on earth

Question 6

What are fossils used for correlating strata referred to as?

Answer 6

fossils that are used for correlating strata are referred to as Index Fossils

Question 7

What 6 criteria must be met in order to be an index fossil?

Answer 7

• have been very common
• have hard parts
• ave a wide geographic range
• lived in many different environments
• have distinctive features
• have a short geological duration

Question 8

What is the use of biostratigraphy?

Answer 8

Allowed strata around the world to be correlated as knowledge of index fossils increased.

Question 9

What is the fundamental unit of biostratigraphy?

Answer 9

the biozone

Question 10

What is the biozone?

Answer 10

The body of rock between the first appearance of an organism and the last appearance of an index fossil species.

Question 11

What led to the geologic time scale being developed?

Answer 11

work on biozones around the world during the 19th century

Question 12

What does the geological timescale rely on?

Answer 12

chronostratigraphy

Question 13

What is chronostratigraphy?

Answer 13

• the branch of stratigraphy that studies the age of rock strata in relation to time
• relies heavily on isotope geology to derive absolute ages of stratigraphic units

Question 14

What resulted from the combination of lithostratigraphy and biostratigraphy?

Answer 14

Allowed relative correlation first throughout Europe, and then to other continents.

Question 15

What made it possible to determine the absolute age of rocks?

Answer 15

discovery of radioactive decay

Question 16

What is the most important tool for establishing a numerical age of rocks?

Answer 16

radiometric dating

Question 17

What is half-life?

Answer 17

radioactive materials decay at a predictable rate

Question 18

Atoms decay from one for (___) to another (___product).

Answer 18

• parent

- daughter product

Question 19

What happens after one half life has passed?

Answer 19

half the original parent material remains, with the rest having been decayed. After another half life, a quarter remains and so on and so forth

Question 20

How can you date the rock radiometrically?

Answer 20

By comparing the ratio of parent material to daughter material

Question 21

Is it possible to radiometrically date all rock types?

Answer 21

no, it is only possible to date igneous rocks

Question 22

What must the boundaries between chronostratigraphic units be?

Answer 22

• instantaneous (represents zero time) and

- isochronous (the same everywhere)

Question 23

What forms the basis of geochronological units?

Answer 23

the boundaries between chronostratigraphic units being instantaneous and isochronous

Question 24

What is a geochronological unit?

Answer 24

interval during which each chronostratigraphic unit was formed (eras, period, stage)

Question 25

What has a formal name?

Answer 25

each period and each stage

Question 26

What are the grouping of different periods into eras based on characteristic fossils resulting from John Phillips in the mid 1800s?

Answer 26

• Paleozoic (ancient animal life)
• Mesozoic (middle animal life)
• Cainozoic (recent animal life)

Question 27

What are the paleozoic, mesozoic, and cenozoic all based on?

Answer 27

overall patterns in changing abundance of different invertebrate groups; as it turns out, major mass extinctions