Historical Geology - Correlation and Dating

Question 1

What are Steno’s Principles?

Answer 1

• superposition
• original horizontality
• lateral continuity

Question 2

What is superposition?

Answer 2

Younger rock layers over older rock layers

Question 3

What is original horizontality?

Answer 3

Deposited in horizontal layers as a liquid to fill in spaces at the bottom but smoothed out at the top.

Question 4

What is lateral continuity?

Answer 4

Layers of sediment are continuous, unless a barrier prevents the sediments from spreading during deposition, or subsequent changes in the landscape break those sediment layers apart.

Question 5

What is the principal of cross-cutting relationships?

Answer 5

New geologic features disrupt (cut) older ones.

Question 6

What is stratigraphy?

Answer 6

The study of rock strata, especially the distribution, deposition, and age of sedimentary rocks.

• Stratified rocks
• geometric relations
• compositions

Question 7

What is Smith’s map based on?

Answer 7

The principle of fossil succession.

-fossils occur in a predictable order in rock.

Question 8

What is correlation?

Answer 8

The process of demonstrating correspondence between geographically disparate stratigraphic units.

Question 9

What is disparate?

Answer 9

Different - not comparable.

Question 10

What is lithostratigraphic correlation?

Answer 10

Linking rock units of similar types..

Question 11

What is temporal correlation?

Answer 11

Linking rock units of a similar age.

Question 12

What is relative dating?

Answer 12

How to determine the order of events in the rock record.

Question 13

Explain Sedgwick and Murchison’s dispute.

Answer 13

Sedgwick discovered and named the time period known as Cambrian. Sedgwick helped fellow geologist Murchison discover the Devonian period. They were friends until they both wanted to claim the same rock strata for their periods. Sedgwick for Cambrian and Murchison for what he called Silurian. A geologist named Lapworth settled the dispute by assigning the older rocks to the Cambrian period and the newer rocks to the Silurian period then carving out a period called Ordovician for the rocks in between.

Question 14

Sedgwick and Murchison:

Answer 14

• Cambrian and Silurian systems
• Cambrian defined by the rocks it overlaid
• Silurian defined by fossil contents

Question 15

What is Chronostratigraphy?

Answer 15

The element of stratigraphy that deals with the relative time relations and ages of rock bodies.

Question 16

What is a Chronostratigraphic Unit (B.O.R.)?

Answer 16

Bodies of rocks, layered or unlayered, that were formed during a specified interval of geologic time (the geochronologic units).

Question 17

What is the Cretaceous system defined by?

Answer 17

The deposition of chalk units with particular index fossils.

Question 18

What is a geochronologic unit?

Answer 18

Period of time.

Question 19

What is the difference between chronostratigraphic units and geochronologic units?

Answer 19

Geochronological unts are periods of time, thus it is correct to say that Tyrannosaurus rex lived during the Late Cretaceous Epoch.

Chronostratigraphic units are geological material, so it is also correct to say that fossils of the genus Tyrannosaurus have been found in the Upper Cretaceous Series.

Question 20

Are the cretaceous deposits of the dinosaur park formation in Alberta a part of the Cretaceous system?

Answer 20

No

Question 21

Explain Sedgwick and Murchison’s dispute.

Answer 21

Sedgwick (did not believe in evolution) discovered and named the time period known as Cambrian. Sedgwick helped fellow geologist Murchison discover the Devonian period. They were friends until they both wanted to claim the same rock strata for their periods. Sedgwick for Cambrian and Murchison for what he called Silurian. A geologist named Lapworth settled the dispute by assigning the older rocks to the Cambrian period and the newer rocks to the Silurian period then carving out a period called Ordovician for the rocks in between.

Question 22

What is an Index Fossil?

Answer 22

A species or genus whose fossils are characteristic of a particular span of geologic time and are used for relative dating.

Question 23

What makes an index fossil?

Answer 23

• Abundant (easily found)
• Easily identified and differentiated from other fossils
• Geographically widespread
• Have relatively short age or stratigraphic ranges

Question 24

What is Biostratigraphy?

Answer 24

Branch of stratigraphy which focuses on correlating and assigning relative ages to rock strata using the fossil assemblages (groups) within. The aim is to demonstrate that two different areas (different deposits) are the same age because they have similar fossils in them.

Question 25

What is Biozone?

Answer 25

a biostratigraphic unit. A body of rock defined on the basis of is characteristic fossil taxa. (Taxa is a group of one or more populations of organisms.)

Question 26

What is Magnetostratigraphy?

Answer 26

Use of magnetic properties of rock for relative dating and correlation.

Question 27

How are absolute ages calculated?

Answer 27

Via radiometric dating methods.

Question 28

What is absolute age?

Answer 28

It is the age of a rock unit, fossil or geologic event expressed in units of time, such as years. A good example is your birthday. You were born at a specific time on a specific day of the year.

Question 29

What are isotopes?

Answer 29

• atoms of the same atomic number
• atoms that have different atomic masses
• different forms of a single element that differ in the number of neutrons in the nucleus