Assignment II (3 pts extra credit on Exam 2)

Geologic Sequences

due October 27^th, at the beginning of class

The purpose of this assignment is to assist you in reconstructing the sequence of geologic events from cross sections, using the relative age indicators discussed in class and in the text.

List the sequence of geologic events represented in each of the geologic cross sections provided on the next page. Remember that an event could be depositional (e.g. deposition of a sandstone), erosional (e.g. to form an unconformity), deformational (e.g. faulting), igneous (e.g. intrusion of a dike), or metamorphic (e.g. regional metamorphism to form a schist). Label the first (oldest) event 1, with successively younger events using higher numbers.

Note that there may be more than one "correct" sequence consistent with the cross section. Such potential ambiguity is inherent in working with rocks that only partially preserve their geologic history. The number of event will vary between cross sections, however no cross section should have more than 13 or 14 events; some may have as few as 6.

Your answers should be in the format given below (with A provided for you) on a separate sheet of paper. You do not need to turn in this handout.

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A.

7 = erosion

6 = deposition of second limestone

5 = deposition of second sandstone

4 = erosion to form a disconformity

3 = deposition of first limestone

2 = deposition of first sandstone

1 = deposition of shale