Lab Exam Flashcards
In an anticline, is the rock in the middle at the surface the oldest or youngest?
Oldest
In a syncline trough, is the rock in the middle at the surface the oldest or the youngest?
Youngest
In an asymmetric anticline, is the rock in the centre the oldest or the youngest?
Oldest
In a plunging anticline, is the rock in the centre at the surface the youngest or the oldest?
Oldest
In a dome, is the rock at the centre of the surface the youngest or the oldest?
The oldest
In a basin, is the rock in the centre at the surface the youngest or the oldest?
The youngest
What is a thrust fault most similar to?
A reverse fault
Identify these unconformities.
Top left: disconformity
Top right: angular unconformity
Bottom: nonconformity
What is this called?
A strike-slip fault.
What is a nonconformity?
Sedimentary rock layered on top of igneous or metamorphic rock
In a disconformity, what is the separation between the layers called?
A depositional break
What is this symbol used to represent?
A plunging anticline
What is this symbol used to represent?
A plunging syncline
What is this symbol used to represent?
Horizontal bedding
What is this symbol used to represent?
Vertical bedding
What is the law of superposition?
It states that younger, sedimentary rocks overlie the older ones
What does the law of cross cutting relations state?
Intrusive rocks are younger than the rock they cut across or intrude
What are index fossils used for?
Can be used to correlate rocks in a separate area
Is the law of superposition relative or absolute dating?
Relative
Is radiometric dating absolute or relative?
Absolute
Are cross-cutting relations relative or absolute in terms of dating?
Relative
Is the use of index fossils absolute or relative dating?
Relative
What are some common radioactive parent isotopes?
C14, Rb87, K40, U235, U238
How is radiometric dating used to obtain the age of a type of rock?
Each radioactive isotope (parent) decays to the daughter isotope at a constant rate, exponentially. The half-life is the time required for half of the parent isotope to decay. After two half-lives, 1/4 remains, after three, 1/8, etc.
What is the half-life of carbon? What is the oldest a rock can be for carbon dating to work?
The half-life of carbon is 5570 years. After 50,000 years, all of the radioactive parent isotope has decayed to the daughter isotope (nitrogen). Therefore it does not work because the upper limit of carbon dating has been reached.
Is this a marine transgression or regression?
Regression
Is this a marine transgression or regression?
Marine transgression
Which type of sedimentary rock is the least resistant to weathering? Which is the most?
Least: shale
Most: sandstone (more quartzite)
What are the five types of sedimentary rocks composed of calcite?
Micrite, coquina, limestone, chalk, travertine.
What are the principles of relative stratigraphic dating?
- Principle of superposition
- Cross-cutting relations
- Fossil dating using index fossils
What is a principle of absolute dating?
Radiometric dating
What is the half-life of carbon?
5570 years
