25 points
Name ______________________________________
Rox & Miners-R-US Inc. have spent a considerable amount of money to finance the exploration of an
area that may house multiple massive sulfide deposits of nickel and copper. These deposits are
associated with a specific type of plutonic rock that is 100-145 Ma (millions of years old). You have
been hired to augment the work of one of the field geologists who took on another project. You must
locate the potentially economical plutonic rocks and distinguish them from other non-economical
plutonic bodies in the area. Your job is to determine if the plutonic rock in the cross section below is a
candidate for exploration or not. Field data of your first potential exploration target is provided.
1. Use the laws and principles of relative dating to decipher the geologic history or the area starting
with the oldest unit. Consult the geologic time scale in your text or the one provided in the
Supplementary Content section of our Geologic Time Lesson Page for the names and numeric ages of
the time intervals for units Q, P, and R. (8 points)
Hints: There are 13 events. Remember to include periods of erosion as separate events.
Unit B is a gabbro, the rest are sedimentary rocks.
Unit Q contains trilobite fossils that are Cambrian in age.485 541 ma
Unit P contains an amphibian-like index fossil that has an age range of 300-330 Ma.Carboniferou
Unit R contains coral fossils that are firmly Triassic in age.201
252 Ma
There are half arrows showing the relative motion along a fault where the crustal block on
the left-hand side has moved down relative to the block on the right-hand side.
Start at the bottom of the cross-section (the principle of superposition).
Preface your events with verbs that indicate the correct process for the rock type/event:
For sedimentary rocks use “deposition of ______”.
For intrusive igneous rocks use “intrusion of ______”.
For extrusive igneous rocks use “extrusion of ______”.
For unconformities use “erosion of ______”.
For faults or folds use “formation of fold or fault.”
For tilted layers use “tilting of units ______”.
For metamorphism use “metamorphism of ______”.
If you’re using contact metamorphism, you can list “metamorphism of _____” in the
same event as “intrusion of _____” or “extrusion of _____” because they are occurring
simultaneously. Example: intrusion of F and metamorphism of M, N, and O.
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