relative dating

Question 1

what are the limitations of relative dating? x3

Answer 1

no info on how long it took for each bed to be laid down
difficult to sort highly deformed/ inverted strata
difficult when unifossiliferous or missing due to erosion

Question 2

what are the four stratigraphic methods of relative dating?

Answer 2

original horizontality
principles of superposition
included fragments
cross-cutting relationships

Question 3

Describe original horizontality

Answer 3

Most sedimentary rocks are deposited as beds; breaks in deposition= bedding planes. beds are commonly horizontal if they are tilted its assumed to have happened after deposition.

Question 4

Describe the principle of superposition

Answer 4

states: rocks at the bottom are older than the rocks above and it assumes no inversion. it can be confirmed by checking way up criteria. e.g. desiccation cracks point to oldest rocks and graded bedding is large particles below fine.

Question 5

Describe included fragments

Answer 5

Fragments of older rock found within younger e.g.
xenoliths found in igneous rocks must be older- fragments of country rock that fell into magma due to stopping
derived fossils are older than the sediments they are found in

Question 6

Describe cross cutting relationships

Answer 6

features can only cut through older rock

e. g. dyke cutting through older sediment
e. g. faults through strata