You are reconstructing the history of this area. 1 is the oldest event and 12 wo

Question

You are reconstructing the history of this area. 1 is the oldest event and 12 would be the youngest.

You have the info from the first question. You just need to insert the other units into the time line using the clues. The

Use these 12 things:

A, B, C, D, F, G, K, L and V (together), N, R, S, and the erosion of the granite (nonconformity).

Work this out on PAPER and then enter your answers. You need to use the book to help you determine the order.

Use relative dating principle to help you.

Superposition: older units below younger units

Cross cutting relationships: Younger things (faults, igneous intrusions cut older units)

Hints-

fault (F) is younger than units A, S, K.

Some units are eroded away in some areas. Look at Unit A.

It is found on 3 corners only but it is the SAME rock that is the SAME age but it has been eroded away in other areas.

S and K are found on top of A in one corner-they have been eroded away everywhere else.

(info from question one)

Explanation / Answer

The order of timing of 12 things is asked

A, B, C, D, F, G, K, L and V, N, R, S, and the erosion of the granite (nonconformity).The Stratigraphic laws used to determine the order are: Law of Original Horizontality,Law of Superposition and the Law of Cross-Cutting relations.The order of events is as follows(1 is the oldest and 12 is the youngest) :

1.Formation of the Basement Granite(G)

2.Development of nonconformity on the Granite (no letter is assigned)

3.Deposition of the coarse sandstone(C)

4.Deposition of greenish shale(B)

5.Deposition of tan sandstone(A)

6.Deposition of reddish sandstone(S)

7.Deposition of grey limestone(K)

8.Movement along fault(F)

9.Formation of dike(D)

10.Deposition of older river gravels(R)

11.Erosion to form narrow canyon(N)

12.Eruption of lava flow(L) and formation of volcano(V)

Explanation :

Granite G forms the basement of the stratigraphic sequence and was formed first.Since a nonconformity is an unconformity between igneous rock unit and a sedimentary rock unit, therefore, a nonconformity developed before the deposition of coarse sandstone C. The rock units B,A,S,K were then deposited successively on top of each other in accordance with the law of Original Horizontality and Law of Superposition(older units below younger units).This complete succession is found on the right hand side of the diagram.

Next is formation of fault F as the strata G,C,B,A is elevated on the left side.The rock units S, and K are eroded in this area but the hint is already given that fault (F) is younger than units A, S, K.Therefore, it formed after deposition of the G,C,B,A,S,K.(Law of Cross cutting relations).

Next is the formation of the dike D.Dike D clearly cuts across the fault F therefore, it is younger in sequence.Next is the deposition of the older river gravel.The river Gravel R cuts across/erodes the exposed dike D at one place,hence it is younger in age than dike D.(Law of Cross cutting relations)

After this erosion takes place to form Canyon N which cuts through river gravel R down through the entire succession.(Law of Cross cutting relations).The last event which takes place is eruption of the lava flow (L) and formation of volcano(V) as lava flows are deposited over river gravels R and sweep over the already formed canyon N in the diagram.(Law of Superposition).

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