Figure 8 is the most complex figure yet. See if you can just look at the picture

Question

Figure 8 is the most complex figure yet. See if you can just look at the picture and figure out the sequence of events before reading the caption.

Now answer these questions:

Question #11: Is there evidence in this picture that there was another layer deposited between layer D and layer F? Explain why or why not.   _________________________________________________________________________

Question #12: The caption describes a “zone of contact” forming as the dike intruded into the rock layers. Is this zone of contact shown in the picture? (yes or no)____________

FIGURE 7.4 The body of igneous rock H is the youngest rock unit, because it cuts across all the others. (When a narrow body of igneous rock cuts across strata in this way it is called a dike.) A is the oldest formation, because it is at the bottom of the sedimentary rock sequence that is cut by H. Folding and erosion occurred after D was deposited, but before F was deposited. E is an angular unconformity. The sequence of events began with deposition of forma- tions A through D in alphabetical order and one atop the other. The sequence was folded, and the top of the fold was eroded. Formation F was deposited horizontally atop the folded sequence and the erosional surface, which became angular unconformity E. G was deposited atop F. Lastly, a magma intruded across all of the strata, causing development of a zone of contact metamorphism and cooling to form basalt dike H.

Explanation / Answer

question #11 :

there was no other layer deposited between the layer D and layer F. because, the surface E, separating the layers D and F is an angular unconformity. as we all know that, an unconformity, whether it is angular or some other kind, represents a time of erosion or non deposition, i.e. a hiatus or a gap in the sequence. that means, there was no other depositional event was going on until F started depositing.

in the caption also it is clearly stated that the sequence of events began with deposition of formations A through D in alphabetical order and one atop the other. the sequence was folded, and the top of the fold was eroded. formation F was deposited horizontally atop the folded sequence and the erosional surface, which became angular uncoformity E.

question #12:

yes, the zone of contact is shown in the picture.

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