On a geologic map,if the contacts between sedimentary rock units form a series of parallel lines,with the youngest unit in the center,the underlying structure is a ________.
A)horizontal anticline
B)plunging anticline
C)horizontal syncline
D)plunging syncline

Question

Quizplus · Accepted Answer

Parallel lines on a geologic map indicate a horizontal orientation of sedimentary rock units. In this case, the youngest unit is in the center, which suggests a syncline - a downward-folded structure with the youngest rocks in the middle. If the structure were an anticline, the oldest rocks would be in the center, and the contacts would radiate out from that point. The term "plunging" indicates a fold that is tilted or inclined, but the question does not provide any indication of this, so we can eliminate choices B and D.

On a Geologic Map,if the Contacts Between Sedimentary Rock Units