Lecture 2

Question 1

What can shelf break also be called?

Answer 1

Offlap break

Question 2

Draw and label a passive continental margin

Answer 2

see notes

Question 3

Draw onlap, toplap, downlap, truncation, offlap

Answer 3

See notes

Question 4

Offlaps are shown on chronostratigraphy graphs are what?

Answer 4

Triangles

Question 5

Define onlap

Answer 5

As they build up they move onto the other surface

Question 6

Define downlap

Answer 6

Building down onto older rock as they build out

Question 7

Define offlap

Answer 7

Building out and downwards

Question 8

Define truncation

Answer 8

Cross cutting one another

Question 9

Define toplap

Answer 9

Each unit laps out in a landward direction at the top of the unit, they build progressively seaward

Question 10

What 2 factors determine shoreline position

Answer 10

Accommodation rate (A) and sedimentation rate (S)

Question 11

What does the A/S ratio determine

Answer 11

If the shoreline moves seaward or landward

Question 12

Discuss regression

Answer 12

Regression is the seaward shift of the shoreline, it occurs when sediment supply exceeds accommodation rate (A

Question 13

What does the A/S ratio determine

Answer 13

If the shoreline moves seaward or landward

Question 14

Discuss regression

Answer 14

Regression is the seaward shift of the shoreline, it occurs when sediment supply exceeds accommodation rate A

Question 15

A>S represents regression true or false?

Answer 15

False

Question 16

A

Answer 16

True

Question 17

A>S represents transgression or regression?

Answer 17

Transgression

Question 18

Discuss Transgression

Answer 18

The landward shift of the shoreline, when accommodation rate is greater than sedimentation rate so you are creating the hole faster than you can fill it. A>S and so A/S ratio is >1. What was now in deeper water is deposited in shallower water

Question 19

Does transgression cause a RSL increase, decrease or does it not affect it?

Answer 19

It causes a RSL increase.

Question 20

Does regression need a RSL increase or decrease?

Answer 20

It needs a RSL increase otherwise nothing would be preserved.

Question 21

Define MFS and how it relates to regression and transgression

Answer 21

MFS is the point between regression and transgression where the sea is furthest inland

Question 22

Draw a transgressing and regressing shoreline

Answer 22

See page 3 of notes

Question 23

Regression has what kind of sediment stacking occurring

Answer 23

Progradational stacking

Question 24

Transgression has what kind of sediment stacking occurring

Answer 24

Retrogradational stacking

Question 25

Discuss negative accommodation

Answer 25

Negative accommodation is when there is a loss of space caused by base level fall. A/S < 0 which implies erosion that can be caused by RSL fall.

Question 26

What causes forced regression?

Answer 26

when the shoreline is lower than the previous one

Question 27

What happens to the shoreline during negative accommodation?

Answer 27

It becomes lower than the previous one which causes forced regression to occur

Question 28

How much is preserved during forced regression?

Answer 28

Not usually anything, small amounts can be preserved when RSL pulses up and down

Question 29

what is eroded during forced regression?

Answer 29

The marine shelf

Question 30

What happens when A=S

Answer 30

This is called autoretreat. When A=S, A/S =1. Although they are equal the shoreline will not remain constant, sediment will need to be distributed over a larger area so transgression occurs as the shoreline moves inland.

Question 31

Define autostratigraphy

Answer 31

The variation in stacking if you keep everything constant, what happens naturally due to inherent characteristics and geometry.

Question 32

Define a parasequence

Answer 32

A genetically related sequence of bedsets bounded by marine flooding sequences on top and bottom.

Question 33

Define walthers law

Answer 33

Stacking upwards sequences represent beds that would have been side by side unless there is an unconformity.

Question 34

does walthers law apply if there is an unconformity?

Answer 34

no

Question 35

parasequences can be identified by what features on a sed log?

Answer 35

A rapid change from coarse - fine grained sediment.

Question 36

Increase in accommodation rate causes regression or transgression?

Answer 36

Regression, it starts to prograde out.

Question 37

Decrease in S whilst A is constant causes what?

Answer 37

Transgression

Question 38

what are the 4 types of parasequence stacking?

Answer 38

Retrogradational (back towards land)
Aggradational (mainly vertical)
Progradational (building towards sea)
Degradational (seawards but downwards)

Question 39

When can retrogradational stacking occur, in terms of A and S

Answer 39

When S is constant and A is increasing

When A is constant and S decreases.

Question 40

what 2 things does degradational stacking require to occur?

Answer 40

Erosion to occur and an unconformity

Question 41

Discuss the A and S characteristics of retrogradational, progradational, aggradational, and degradational stacking

Answer 41

Retrogradational stacking occurs when A = constant and S is decreasing or when S = constant and A is increasing.
Aggradational occurs when A and S keep up with one another
Progradational occurs when S = +ve and A = 0
Degradational occurs when S =+ve and A = -ve

Question 42

What are the 3 types of stratal stacking patterns?

Answer 42

• Progradational - Aggradational (PA)
• Retrogradational (R)
• Aggradational - Progradational - Degradational (APD)